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The Clarinet Reed: an Introduction to its biology, chemistry, and physics
Document
Presented in Partial Fulfilment of the Requirements for the Degree
Doctor of Musical Arts in the School of Music
The Ohio State University
By
Donald Jay Casadonte, B. A., M. A.
The Ohio State University
1995
Document Committee: proved by
James Pyne
Christopher Weait
Patrick Gallagher Advisor^ Department,Ç Music DHI Number: 9612138
Copyright 1995 by Casadonte, Donald Jay All rights reserved.
UMI Microform 9612138 Copyright 1996, by DHI Company. All rights reserved.
This microform edition is protected against unauthorized copying under Title 17, United States Code.
UMI 300 North Zeeb Road Ann Arbor, MI 48103 Copyright by
Donald Jay Casadonte
1995 To My Parents and the Blessed Virgin Mary, with the hope that the effort of this work has honored them Acknowledgements
In completing such a complicated Interdisciplinary work It Is almost
Impossible to mention all of people to whom the author Is beholden. In the matter of the biology of the reed, the author thanks Dr. Frederick Sack, Clare
Lawton, Dr. Marilyn Veselac and Dr. Lisa Boucher for their discussions about
Arundo donax, John Mitchell for electron microscopy, Ann Osterfeld and Cathy
Wolken for optical densitometry plots, Richard Pearson for donating a rhizome.
Dr. Richard Swenson, Jose Diaz and LLoyd Lemmermann (?) for photographing the gross anatomy of the plant. Dr. Oliver Tuovlnen, Christine
Vanecko, Dr. Karl NIklas, Steve Lawton, and Matt MIslcka who gave valuable advise or provided equipment. Many other students and faculty of the OSD
Department of Biology conversed wXh the author or helped run tests. Their names are Important and deserve a more complete listing.
In regards to testing the chemistry, physics and material properties of the reed, the author thanks, from OSD: Dr. Patrick Gallagher, Ruth Anderson,
Gordon Renkes, Dr. Billy Culbertson, Dr. Alka Thakur, Paul Herman, Sandy
Jones and Dr. Jerry BIgham, as well as Dr. Ivan Goldfarb of Wright State
University, Dr. Helntz Melneker of the University of Akron, Dr. Andrew Summers of Miami University of Ohio, J. W. Lemmons of J. W. Lemmons and Associates,
Wayne T. Scheer. In addition, a dentlst/obolst’s at the University of Washington
(Dr. Robert ?) for suggested to the author the salic acid deposition from saliva.
Ill Many former students of Dr. Arthur Benade helped the author in acoustical matters: Dr. Douglas Keefe of the University of Washington Department of
Systematic Musicology, Dr. Walter Worman, Dr. Steven Thompson, Dr. Peter
Hoekje.
Thanks go to Tom Merrick, Martin (Marty) Haas, the site assistants at the
OSU computer labs, and Dr. Gary Kinzel for computer help. Dr. Michael
Trudeau and Dr. Joel Weaver of OSU for videotaping the reed vibrating in the mouth. Dr. Arthur Leissa and Dr. Anderson for discussing plate theory and critiquing results. Dr. Brian Harper for reading chapter five, Been-Der Yang and
Mohammed (last name?) for measuring the shape of reeds, Calvin Trefz in the physics department for providing physical testing equipment, and Dr. James
Grotberg, Dr. Guezennec, and Dr. Thorwald Herbert (each suggested the vortex shedding mechanism of reed excitation) for discussing fluid mechanics .
In regards to the musical aspects of the reed, thanks go to my past clarinet teachers, Charles Baker, and professor emeritis. Dr. Donald McGinnis, the document and general examination committees: Dr. Patrick Gallagher,
Christopher Weait, Craig Kirchhoff and Richard Blatti, Dr. Burdette Green for reading and correcting chapters one and two, Robert Sorton and James Hill for advise on reeds, members of ICS and IDRS, Ray Spielman, various posters on the internet for comments, and Dr. Kim Ellis for support. Special thanks go to the student reed rater: Dr. Bruce Curlette, Dr. Daniel Lochrie, and Dr .Melinie
Griffin, Amy Lammendola, Cathy Gardiner, Cathy Hope, Sarah Young, Jennifer
(Sutton) McDonald, Gail Letho, Debra Andrus, Wendy (Welsh) Harvey, Lora
Sabo, Seth Semmons, Beth Stimpert, Carmen Strine, as well as other former clarinetists of the OSU concert band.
iv Thanks goes to the OSU Graduate School (Sandy Walden and Bobbi Davls-
Jones), Elaine Moran of the ASA, and journalists Karen Schmidt, Bret Adkins, and Robert Cooke.
For emotional support, thanks go to Susan Sund, my brothers and sisters in the Third Order of Discaiced Carmelites, who have taught me more about life than I can ever hope to repay, and my brothers and sisters in the St. Micheal
Prayer group for support and prayers. There is not room enough to say all I would wish to my parents, Dominick and Billie Ann Casadonte, and brothers,
Thomas, Michael, and Dominick, for their care over the years. They know what difficulties the author has faced, and the finishing of this document is a testimonial to them.
This document would never have been finished without the extraordinary help of the author’s advisor, James Pyne. He originally invited the author to participate in his idea of forming a clarinet research group six years ago, and has, over the years, been instrumental in obtaining funding and instrumentation. He has coached the author through the rigors of a performance degree program, and taken care of ail of the administrative details which were necessary to obtain the degree. He has discussed many of his own acoustical research projects with the author, and has gone out of his way to be there whenever the author needed his help.
Finally, the author must thank Divine Providence for providing him with so many moments of grace over the last fifteen years while attending to musical matters at The Ohio State University. If this document gives witness to anything, it gives witness to His power to act through weakness, and to bring all things to completeness. Vita
June 19,1955 ...... Born - Cleveland, Ohio
1977 ...... B. A., Case Western Reserve University, Cleveland, Ohio
1982...... M. A., Cleveland State University, Cleveland, Ohio
1979-Present ...... Music Student, The Ohio State University.
Publications
1. "A Center-symmetric Potential Function for use in Liquid-State Modeling," senior research project," Case Western Reserve University, 1977.
2. “An Introduction to the Biology, Chemistry, and Physics of Woodwind Reed Material,” Journal of the Acoustical Society of America, vol. 90, no. 4, part October, 1991 (Abstract).
3. Cane That’s Musically Able (Interview) Science News, December, 14, 1991.
4. Reed Research Interview, Science News Update National Public Radio January, 1992.
5. “The Geometry of Melodic Structure: is there a strange attractor at the heart of Bach’s, Invention no. 4 in d minor?". Journal of the Acoustical Society of America, (abstract).
vi 6. The Hypergraphics of Musical Sounds, MA Thesis, Cleveland State University, 1982.
7. "The Hypergraphics of Musical Sounds", cited in the book. Results of the Chroma Foundation Search for New Music Notation, 1985.
8. “The Biology, Chemistry and Physics of A. donax," paper presented at the International Double Reed Society meeting, Towson State University, 1990.
9. “A tour through Arundo donax," (with James M. Pyne), presented at the International Clarinet Society meeting. University of Cincinnati, 1992.
10. "A Hypothetical Decompactiflcation Model for the Process of Humor," Paper presented to the Western Humor and Irony Membership Conference, Purdue University, 1988.
11. A Hypothetical Decompactiflcation Model for the Process of Humor," abstract in WHIM VIII, 1991, Purdue University Press.
12. "A Hypothetical Decompactiflcation Model for the Process of Humor," cited in the American Society of Aesthetics Newsletter, 1989.
13. "The Dynamics of Humor l-Decompactification Mathematics," and Humor in F: what's so funny about Mozart's Musical Joke?" Seventh International Conference on Humor, Hawahi, 1989.
14. "The Dynamics of Humor II- Chain Ordering and the Energy of Humor," Eighth International Conference on Humor, Sheffield, England, 1990.
15. "Transition Phenomena in Humor," Ninth International Conference on Humor, Ontario, Canada, 1991.
16. “Psychophysiological responses to Humor: a theoretical perspective," CORUUM/Tenth International Conference on Humor, Paris, France, 1992.
17. "Resolving the Mechanisms of Musical Humor: an analytical study of Mozart's Musical Joke," juried competition winning paper. Graduate Research Forum Competition, The Ohio State University, 1989.
18. An Introduction to the Biology, Chemistry, and Physics of Arundo donax," juried competition winning paper. Graduate Research Forum vii Competition, The Ohio State University, 1991.
19. “The Geometry of Music: metric and phase space results," juried competition winning paper. Graduate Research Forum Competition, The Ohio State University, 1992.
20. DMA Solo Recital l-January, 26, 1990, The Ohio State University.
21. DMA Solo Recital ll-February, 1990, The Ohio State University.
22. “Who Killed Mrs. Myheart?" a musical mystery for Corps in Bb and Clarinet, © 1990, Donald Casadonte
Major Field: Music Minor Field: Chemistry
VIII Table of Contents
Dedication ...... ii
Acknowledgements ...... iii
Vita...... vi
List of Figures ...... xii
List of Tables ...... xii
Preface ; ...... 1
Chapter Page
I. Introduction ...... 5
Early Uses of Arundo donax in music ...... 5 Brief History of the Clarinet Reed ...... 9 Modern Manufacturing Techniques for Clarinet and Saxophone Reeds ...... 22 Reed Nomenclature ...... 33 Rationale of Current Study ...... 41
11. Arundo donax Anatomy ...... 50
The Root System ...... 51 The Stem System ...... 58 The Leaf System ...... 71 Ultrastructure ...... 79 Ground Tissue System ...... 95 Vascular Tissue System ...... 107 Cell Walls ...... 124
III. Clarinet Reed Chemistry ...... 132
The Chemistry of Arundo donax...... 132 Elemental Analysis ...... 132 ix Cellulose ...... 134 Degree of Crystallinity by Infrared Spectroscopy ...... 142 Extending the Infrared Testing Method ...... 153 Other Tests for Decrystallization ...... 155 Degree of Polymerization ...... 157 Hemicellulose ...... 159 The Role of Water and Hemicellulose ...... 163 Hemicellulose Degradation ...... 164 Infrared Identification of Hemicellulose ...... 174 Lignin Preliminaries ...... 175 Arundo donax Lignin ...... 180 Spectroscopic Methods of Lignin Determination ...... 181 Cell Wall Chemistry ...... 187 Chemistry and Material Properties ...... 189
IV. Clarinet reed Material Properties ...... 193 Introduction ...... 193 Descriptive Results ...... 196 Mass/Weight Properties ...... 208 Effects of Heat on the Clarinet Reed ...... 216 Effects of Light on the Clarinet Reed ...... 228 The Effect of Saliva on the Clarinet Reed ...... 229 Clarinet Reed Degradation ...... 232 Towards the Prevention of Reed Degradation ...... 239 Reed Hydroscopic Properties ...... 241 Changes in Physical Parameters with Hydration ...... 255 Mechano-sorptive Creep ...... 256 Damping ...... 256 Stress and Strain: Theoretical Considerations ...... 265 Stress and Strain: Empirical Tests and Results ...... 283 Biomorphological Variations ...... 286
V. Reed/Mouthpiece Dynamics ...... 298
Overview ...... 298 One-Dimensional Reed Models ...... 299 One-dimensional Unforced Models of the Reed ...... 302 One Dimensional Linear Models of the Forced Reed ...... 306 Two-Dimensional Reed Models ...... 318 Three-Dimensional Reed Mechanics ...... 325 X Reed/Mouthpiece Interactions: Diffuser Theory and the Origin of Reed Squeak ...... 336 Starling Resistor Model of Lip/Reed ...... 350 Reed Shape Effects ...... 359 Finite Element Simulation of the Clarinet Reed ...... 373
Appendicies A. Sample Reed Rating Instruction Set ...... 384 B. Reed Mode Shapes and Stresses ...... 392
Bibliography ...... 456
XI List of Figures
Figure Page
1.1. Early Reed flute and Pan Pipe...... 7
1.2. Early “Single Reed” and “Double Reed” Instruments...... 8
1.3. Historical Reed Development...... 10
1.4. Clarinet Reed Superellipse Paramenter (N) Variation...... 20
1.5. Effect of Changing N in the Superellipse Equation...... 21
1.6. Computer Superellipse of 1/2 Reed Tip (N = 1.786)...... 23
1.7. The Var Region of Southem France...... 24
1.8. Steps in Reed Manufacturing...... 25
1.9. A Biomorphological Miscellany ...... 29
1.10. Common Reed Nomenclature...... 34
1.11. The Reed Grid...... 35
1.12. The Wedge Profile...... 37
1.13. The Expanding Ridge (Crest) Profile...... 39
2.1. Arundo donax Taxonomy ...... 51
2.2. A Sample of Grasses at The Ohio State University...... 53
2.3. The Arunc/o donax Stem ...... 56
2.4. The Rhizome...... 60 xii 2.5. The Complete Arundo donaxCu\m ...... 62
2.6. Arundo c/onax Cross-section (Stele)...... 63
2.7. Arundo donax Intemodes and Nodes...... 64
2.8. Nodal Sites for Leaf Generation...... 65
2.9. The Processed Stem...... 68
2.10. The Three Tissue System...... 70
2.11. Arundo donax Leaf Pattern...... 72
2.12. Panicles...... 75
2.13. Panicle and Base Structure Showing Subdivisions of Aggregate....76
2.14. Spiklets...... 78
2.15 Spiklet, Glume, and Floret...... 79
2.16. Florets...... 80
2.17. Perianth...... 81
2.18. Three-Component Structure of Arundo donax Stem Material...... 83
2.19. Epidermis Schematic...... 85
2.20. Electron Dispersive X-ray Spectrum of Arundo donax Stem Epidermis...... 86
2.21. Electron Dispersive X-ray Spectrum of Arundo donax Stem Inner Tissue...... 87
2.22. A Tannin (Catechin) Structure...... 88
2.23. Subepidermal Sclerenchyma Tissue...... 90
2.24. Veselac’s Two Locations for Fiber Bands...... 93
2.25. Fibers and Sclereids...... 94
2.26. Bundle Sheath...... 96 xlii 2.27. Parenchyma Tissue...... 98
2.28. Parenchma I opology ...... 102
2.29. Parenchyma “Sheet”...... 104
2.30. Parenchyma Unit Crystal Approximation ...... 105
2.31. Vascular Bundle...... 108
2.32. Various Steles...... 110
2.33 An Explanation of the Vascular Bundle Power Law...... 111
2.34. Xylem Cells...... 113
2.35. Phloem Cells...... 115
T» 2.36. An Explanation of the Collateral Arrangement of Cells in the Vascular Bundles of Arundo donax ...... 117
2.37. Xylem Fiber...... 119
2.38. Companion Cells...... 120
2.39. Pits...... 122
2.40. Helical Thickening...... 123
2.41. An Explanation of Turgor Pressure...... 125
2.42. The Cell Wall...... 126
2.43. The Fibril Concept...... 128
3.1. 3-d-glucopyranose...... 135
3.2. Cellobiose...... 135
3.3. 1—>4 3-d-glucopyranose Bridge Structure...... 136
3.4. Cellulose Polymer Structure...... 137
3.5. Cellulose Crystal Structure...... 138
xiv 3.6. X-ray Detraction Spectrum of Clarinet Reed...... 141
3.7. Superimposed 020 Peaks for Spent and Pristine Reeds...... 146
3.8. Clarinet Reed infrared Spectrum...... 149
3.9. %C from Infrared Data for Selected Reed...... 152
3.10. Pristine and Spent Infrard Spectra...... 154
3.11. Differential Scanning Calorimetry Plot of Pristine and Spent Reeds...... 156
3.12. Arundo donax Hemicellulose...... 161
3.13. TGA Spectrum of Two Pristine Clarinet Reeds...... 166
3.14. TGA Spectrum of Two Spent Clarinet Reeds...... 170
3.15. Comparison of Differential Plots of Pristine and Spent TGA Spectra...... 172
3.16. Lignin Preliminaries...... 176
3.17. Infrared Spectrum of Arundo donax Stem...... 183
3.18. Infrared Peak Assignments for Arundo donax Spectrum...... 185
4.1. Overall Ratings for {R}...... 197
4.2. Descriptive Statistics for Reed Quality Rating...... 198
4.3. Timbre Ratings for {R}...... 200
4.4. Strength Ratings for {R}...... 201
4.5. Noise Ratings for {R}...... 202
4.6. Stability Ratings for {R}...... 203
4.7. Projection Strength Ratings for {R}...... 204
4.8. Summary Statistics for {R} ...... 205
4.9. Pearson Correlation Matrix for Performance Descriptors...... 205 XV 4.10. Mass Measurement Summary...... 211
4.11. Mass Statistics...... 210
4.12. Mass and Quality Descriptor Correlation Matrix...... 213
4.13. Contour Density Map of Oboe and Clarinet Reed...... 215
4.14. Optical Density Map of a Clarinet Reed Tip...... 217
4.15. Cross-sectional Optical Density...... 218
4.16. Stem Orientation...... 222
4.17. Thermal Expansion Curves for Arundo donax...... 223
4.18. Coefficient of Thermal Expansion for Arundo donax ...... 221
4.19. Shape of S. Epidermitis and its Migration in Reed Pit Cells...... 234
4.20. Bacterial Deposition on inner Xylem Wall...... 235
4.21. Bacterial Biomass...... 236
4.22. Bacterial Sheet (Heinrich’s “Fungus”)...... 237
4.23. Clarinet Reed Water Capacity...... 243
4.24. Water Adsorption on Cell Walls...... 245
4.25. Sorptive Hysteresis...... 247
4.26. Longitudinal and Transverse Reed Warp...... 249
4.27. Reed Warp Measurments, Pristine/Played...... :...... 250
4.28. % Warp for Pristine and Played Reeds...... 251
4.29. Water Transport Mechanism in Clarinet Reeds...... 253
4.30. Creep...... 257
4.31. Arundo donax Decay Curve (blow-up)...... 259
4.32. Arundo donax Decay Curve, Complete...... 261 xvi 4.33. Comparison of Wood and Arundo donax Decay Curves...... 264
4.34. Mass-Spring System...... 266
4.35. Cellular Spring Network...... 268
4.36. Young’s Modulus...... 270
4.37. Orientation of E and G Moduli...... 272
4.38. Two Diffemt Uses for Mohr’s Circle...... 275
4.39. Poisson’s Ratio...... 277
4.40. Viscoelastic Circuit Models...... 280
4.41. Typical DMA Plot ...... 285
4.42. Vascular Bundle Number in a Sample of Reeds...... 288
4.43. Vascular Bundle Statistics...... 289
4.44. Vascular Bundle/Quality Correlation Matrix...... 289
4.45. Different Types of Fiber Arrangements in Clarinet Reeds...... 291
5.1. A Comparison of Measured and Computed Reed Shapes...... 333
5.2. The Clarinet Moutnpiece and Reed...... 337
5.3. Flapping Flutter and Reed Squeak...... 345
5.4. The Starling Resistor Model...... 352
5.5. Reed Structural Factor: Heel Thickness...... 363
5.6. Reed Structural Factor: Uncompressed Shoulder Height...... 364
5.7. Reed Structural Factor: Compressed Shoulder Height...... 365
5.8. Reed Structural Factor: Tip Thickness...... 366
5.9. Reed Structural Factor: Thickness...... 367
5.10. Reed Structural Factor: 8mm, Left Thickness...... 368 xvii 5.11. Reed Structural Factor: 8mm, Right Thickess...... 369
5.12. Reed Structural Factor: Natural Frequency...... 370
5.13. Correlation Matrix for Structural Measures...... 371
5.14. Finite Element Grid Measurements...... 375
5.15. Modal Measurement Set-up...... 377
B.1. Reed Modal Shapes and Stresses...... 398
XVII! List of Tables Table Page
2.1. Comparative Size of Arundo donax Anatomical Elements...... 129
3.1. %C Data for Pristine and Spent Reeds...... 144
5.1. Statistics for Reed Structurai Measures...... 362
XIX Preface
The flow of fluids around structures, ranging from clarinet reeds to skyscraper, can cause destructive vibrations as well as useful motion...
-Robert Blevin, Flow-Induced Vibrations'^
A thorough search of the literature pertaining to the clarinet reed (see
Shea for such a list) reveals a large number of articles on practical issues, such as reed preparation and scraping, but few articles concerning scientific aspects of the reed. Neither the biology (except for Perdue’s introductory work and Veselac’s landmark dissertation), the chemistry
(indeed, there is no source outside of the chemical literature for information on reed chemistry), nor the physics (although, to be sure, in this area there have been a few articles with broad implications on topics such as reed resonance) have been covered to any great extent.^
At this point in history, the lack of information on the clarinet reed can no longer be dismissed with the remark that the undertakings necessary to remedy the situation are beyond the reach of current science. Advances in material science, physics, chemistry, and botany are such that many of the questions clarinetists would like to have answered about the reed and its
1 2 behavior are now within the capabilities of researchers to do so. This document is intended to be a first step in that process of the scientific study of the clarinet reed.
Because this task it has had to be interdisciplinary in nature from the outset, however, a few words are in order for both the musician and the scientist who, of necessity, must confront each other in the course of these pages. The author has decided to write each section, musical or scientific, at a level which is as close to a professional discussion of the research presented in the area as possible, while acknowledging that its principal readership will, in all likelihood, be drawn primarily from non-specialists in that area. This decision was made in order to avoid dwelling too extensively on background material.
Little explanation is given for such things as differential equations, for example, or the workings of the electron microscope, most standard laboratory equipment, or even how to hand-make a clarinet reed-to do so would simply have expanded the document well beyond the confines of reason. Because, however, there is probably no one reader who is well versed in all of the areas presented in this document, where it would increase ease of presentation, the author has provided “essential” background for some of the tests, chemical and reed nomenclature, etc. In addition, the author has introduced each new term used by bold-faced type to make them easier to find for the reader’s reference.
In order to bridge the gap between art and science, a discussion is made 3 of not only the scientific implications of the findings contained herein, but also a discussion of the musical implications as well. Although not all questions about the clarinet reed could be answered given the limitations of resources for this research, hopefully some of the questions which have been the source of frustration, guesswork and folk wisdom over the years will be answered herein, and in some cases, misconceptions corrected.
As simple as the clarinet reed appears to be, the scientific effort required to understand it is, nevertheless, not small. Many of the concepts needed to explain the reed behavior on a material and physical level are at the forefront of current scientific knowledge. It is hoped that this document will help to motivate other people, far better qualified than the author, to bring their own expertise to the problem of the clarinet reed.
The relationship between the musical arts and the physical sciences is very old. It is hoped that this document will help extend that relationship a little farther. Endnotes
1. Robert Blevins, Flow-Induced Vibrations (New York: Van Nostrand Reinhold Co., 1990): 1.
2. David Shea, “The Clarinet Reed: A Bibliographic Addendum”. The Clarinet Magazine (November/December, 1990): 28-29; Robert E. Perdue, Jr., “Arundo donax-Source of Musical Reeds and Industrial Cellulose.” Economic Botany, vol. 12, no.4 (Oct.-Dec). Industrial Cellulose”. Economic Botany, 12, no.4 (Oct.-Dec, 1958): 370-390; Marilyn Sue Warren Veselac. “Comparison of Cell and Tissue Differences in Good and Unusable Clarinet Reeds” (Ph.D diss.. Ball State University, Muncie, Indiana, 1979); Stephen Thompson, “The Effect of Reed Resonance on Woodwind Tone Production,” Journal of the Acoustical Society of America, 66, no. 5 (May-June, 1979): 1299-1307. Chapter I
Introduction
Early Uses of Arundo donax in Music
Of the three essential elements in the tone production of single-reed woodwind musical instruments-the resonating tube, the mouthpiece, and the
"reed", the most temporary and variable is the reed, because is usually consists of some form of plastic or semi-plastic (bio)polymeric substance which is subjected to both chemical and mechanical degradation during its use. The material still most commonly used to produce the characteristic sounds of the clarinet and saxophone families of musical instruments is naturally occuring--the stem of the monocotyledonous grass, Arundo donax L ,
(commonly, giant reed plant) .
Before it was used in the construction of woodwind reeds, however,Arundo donax, a relative of the bamboo family of plants (although definitely not bamboo, as is sometimes thought) was used primarily to form the entire body of primitive types of musical instruments. It was originally utilized as it occurred, in situ, by cutting portions of the long hollow cylindrical stem (having a cross-sectional diameter on the order of one inch) to a suitable length for the body of the instrument. The earliest known examples of such musical adaptations of the plant stem date back to the prehistoric forms of reed flutes and Pan pipes (an instrument consisting of many hollow tubes of different lengths coupled together in a row, functioning much as a row of glass bottles of different lengths-each pipe sounding a different pitch depending upon which segment is blown into (figure 1.1)).1
Some time before 3000 B. C. two new classes of musical instruments were developed in which some part of the musical instrument itself was set into motion by air passing from the lings into the air column (the direction of flow is indicated by the letter U in figure 1.1). In the double reed variety of instruments, the vibrating portion was separate from the body of the instrument, and may have been developed in primitive cultures as a result of a simple experiment in placing two thin reed slivers together and blowing. It is not our purpose here, however, to develop the long and complex history of double reed instruments.
The details of early double reed instrument history will be deferred to the many fine texts on musical organology currently available.^
The single reed variety of these early reed-driven instruments consisted of the hollowed tube of Arundo donax having a long rectangular segment cut into one end near the opening of the tube which acted as a vibrating tongue or
"squeaker" activated when the player blew through an open end (figure 1.2).
The instrument was often cut with several tone holes and mounted tandem to a second tube which sounded a single drone note.
Scholars are uncertain which of the two prototypical classes of single or double reed instruments developed first.3 Reed Flute Mouthhole Ô a o D Arundo donaxintemode
Pan Pipes
Arundo donaxintemode Frequency increasing U (= air flow' vector) ^Coupling Box
Figure 1.1-Early Reed Flute and Pan Pipe 8
Arundo Donexlntemode
U D
Prototype Double Reed Instrument
Arundo Donaxintemode Sque^er Flap ( "Reed") O CD CD O Qf
Drone■
Prototype Single Reed Instrument v ith Drone
Figure 1.2-Early “Single Reed” and “Double Reed” Instruments Although the double reed variety of such instruments flourished historically, assuming a variety of guises from bagpipes to racketts to early oboes, single reed instruments remained in their undetached squeaker form, except for some curious examples where reed slivers were mounted to tubes of ivory or metal which served as a holder.4 Despite being used for two thousand years, a clear-cut detached single-reed system does not seem to have developed at all before the late seventeenth century.s
A Brief History of the Clarinet Reed
The use of detached single reeds placed over a mouthpiece opening appears to have developed simultaneously with the first chalumeau (late seventeenth century). In fact, the name itself, "chalumeau", derived from the
Latin word, calamus, meaning, "a small reed", attests, somewhat, to this fact.e
According to a surviving chalumeau produced about 1700 by the famous
Nuremberg instrument maker, J. C. Denner (which may even possess a contemporaneous reed), the first "clarinet" reeds were very wide-1.5 cm. vs.
1.35 cm. for modern reeds-being mounted to equally wide mouthpieces. They were essentially rectangular in shape, with no rounding nor tapering at the tip (it was, essentially, a flat, rectangular plate), had a longer vibrating length relative to the clamped portion than modem reeds (figure 1.3), and were somewhat thicker than modern reeds- a feature accommodated by the less restricted acoustic requirements of earlier instruments. The wider, flatter, and thicker reeds allowed a looser, more flexible embouchure to produce a sound.7 10 1.5 cm Top 1.35 cm Superelliptical View Roundijig 1 1.2 cm Square Tip (N=oc) (N«1.5-3?) I V 2b 3.0cm ^ 3.35 cm {
1.2cm
} 2.1 cm { 3.4cm a. 1:3 Era Reed (1 7 2 0 -1 8 20) b. 2:3 Era RsecK 1820-1860) Cross-sections I c. 3:3 Era Reed (I8 6 0 -) 1 . C = 3 Ground Tissue Epidermis—
2 - W E■Vibratingw,k Clamped" 3. O Surface
Side View Front Vamp Back Vamp Front Vamp Back Vamp
Superelliptical Tip Rounding:
(2Lf”+ (lf = 1 a b
Figure 1.3-Historical Reed Development 11
Although the Encyclopédie of Diderot and D'Alembert (1751-1765) contains an engraving of an early clarinet reed, most of the evidence as to their construction and shape is scant and inferential.8 The first single reeds made specifically for the clarinet appear to have been little more than thin rectangular slabs about 1 mm. thick. The rectangular shape is probably derived from the
rectangular "squeakers" of the older single-reed pipes. This conjecture is supported by the fact that when these earliest plate-iike reeds are afixed to the mouthpiece the similarly to the reed squeaker arrangement of figure 1.2 is unmistakable.9
A simpie development would have been to remove the rectangular squeaker completely from the body of the squeaker-borne instrument and attach it to a separate mouthpiece, retaining, in the process, both the squeaker (now, detached) and the window opening through which the squeaker (reed) could move. Early mouthpieces were little more than tube extensions of the chalumeau body, being practicaliy continuous with the instrument, making the resemblance to squeaker-driven instruments evenc le a r e r.io
In retrospect, the design for the early reed, in which the lengthwise tapering common to all modern reeds is lacking, may seem strange to players of today, accustom as they are to having a thin tip from which to produce the tone, however, given the mouthpiece design of the earliest clarinets, with the interior chamber showing very little taper compared to modern mouthpieces, flat plate reeds would have been quite stabie (the book by Baines contains an interesting x-ray of an early clarinet, showing the interior of a mouthpiece in detail).n 12
We shall show in chapter five that the thickness variation of a reed is a direct function of the volume variation inside of the mouthpiece chamber. Since modern mouthpieces contract towards the tip, the reed must be made thinner at the tip to balance the forces generated inside of the mouthpiece, which decrease as one approaches the tip of the mouthpiece (although at the very tip other physical forces, such as Bemoulli forces, increase the pressure over this small region). The earliest mouthpieces, being almost constant and cylindrical in chamber shape would require reeds equally as uniform in thickness. Thus, the simple plate-like shape of the earliest reeds would have been appropriate for the instrument of the time. In any event, this primative reed shape makes vibration analysis very simple, as it is easily approximated by a simple rectangular beam or even a thick plate (chapter five).
The earliest reeds, specifically designed for the clarinet, had a playing surface
(the region of exposed cane) about 3 millimeters (mm.) shorter than modern reeds, judging from photographic evidence of early mouthpieces contained in organological references, such as the The New Grove's Dictionary of Musical
Instruments.^^ In the aforementioned work, in the article entitled, "Clarinet," sample photographs of old and modern mouthpieces and reeds are presented.
Since the sizes of both modern mouthpieces and reeds are known precisely, these values may be used to scale the other photographic measurements of earlier mouthpieces and reeds to correct size.
Using this approach, the vibrating surface of the reed, which is the portion placed in the player's mouth (called the front vamp or, more commonly. 13
simply, the vamp), Is 3 cm. for the earliest reeds (ca. 1760) vs. 3.35 cm. for a
modern reed (figure 1.3).
These measurements are under the assumption that the vibrating portion of
the reed is coincident with the opening (called thewindow ) in the clarinet
mouthpiece. This may or may not be a valid assumption. It does seem to be
supported by iconographie evidence, such as from VneEncyclopedie^ mentioned
above. F. Geoffrey Rendall, the clarinet historian, has also advocated this
photographic method of inferring reed dimensions from available contemporary
mouthpiece s h a p e s js indeed, since early reeds are all but nonexistent, this
inferential approach may be the only general way to derive even approximate
information about the development of the clarinet re e d . 14
The epidermal or unexposed clamped part of the earliest reeds (we call this the back vamp) was very short, gradually lengthening as time went on: 1.2 cm.
(ca. 1760) vs. 2.1 cm. (ca.1850) vs. 3.4 cm. (modern). The reason for this
difference in length is that the table, i.e., the flat portion of the mouthpiece against which the back vamp rested, was much shorter on early mouthpieces than modern ones, only gradually reaching down the full length in the late
nineteenth century.
The evolution of the mouthpiece allows one to draw some conclusions about the evolution of the clarinet reed. Denote the ratio of the back vamp length to the
front vamp length as rbf. Acording to measurements of the tip shape and table
lengths of photographs of old mouthpieces (realizing that the conclusions
drawn are based on a limited sample), the development of the clarinet reed may 14 be divided into three somewhat arbitrary but convenient eras according to gradual change in the rbf parameter: the 1:3 era, the 2:3 era, and the 3:3
(1:1) era, respectively (figure 1.3).
The 1:3 era (1720 to 1820) was characterized by ultra-short back vamps (1/3 of the length of the front vamp). There is some variation in the rbf in measured drawings, with one by Geoffrey Rendall having a 1:4 ratio.15 |n any case, this period has the largest overall value of the rbf parameter (typically, 1:3, more or less). The front vamps of the earliest reeds, in addition, were shorter and wider than modern reeds. Reeds of this era were played against the upper lip, and were either rectangular or (later on in the era), rounded at the tip. A mouthpiece made in 1780 in Paris shows unmistakable rounding at the tip.i6
The detailed profile of the reed varied enormously during this period. The earliest reeds (1720-1750), as mentioned, were fairly thick, flat plates ofArundo donax. After 1760, several other shapes began to emerge. Baines reports that the Tutor by Backofen (1803) is the first to give a detailed account of the reed shape. 17
According to Backofen, at the turn of the nineteenth century the tapered reed tip had not yet gained universal aceptance. The older flat plate reed, about one millimeter thick at the tip, coexisted along with the newer tapered tip reed. The tapered reed of the era, being shorter, thicker at the tip, and thinner than a modern reed, had a correspondingly shorter moment arm. Such a reed would probably feel "stiff if played on modem instruments (interestingly, the Vandoren
Black Master reed comes close to this historical profile). In any event, the 15 mouthpiece and air column of the time would have compensated for this resistance.
The transverse (width-wise) cross-section of the reed could be, according to
Backofen, uniform and rectangular (as in the flat plate) or convex on both the top and the bottom of the reed or even flat on the top and concave underneath
(since the reeds of this era were played "upside-down" compared to modern reeds, the flat "top" refers to the part facing the mouthpiece, so that the cross- section is equivalent to the modern reed shape), as in figure 1.3.
Whatever the cross-section, the reeds were generally thicker than modern reeds. The contemporary clarinetist, Muller, however, comments that such reeds were hard to c o n tro l.18 |n addition, such thick reeds required that the lay be very long to create the forces necessary to the physics of the reed (chapter five). When thinner reeds were accepted, the mouthpiece requirements were relaxed, allowing for the shorter lay which is used today, and consequently, greater control of the physical motion of the reed. The reed of this era, with a thinned tip, is probably the type which was used by professionals during and after Mozart's time.i9
Along with the variations in length and cross-section during this era, the width of the reed also changed- from 1.5 cm. in the earlier part of the eighteenth century to as small as 1.2 cm. in German reeds of the later part of the century (even today, German reeds tend to be narrower than other reeds, maintaining the 1.2 cm. width).so These changes are reflected also in the 16 narrowing of the mouthpiece window, especially at the bottom of the window, so that a quasi- "v" shape, with a top window opening of .93 cm. and bottom window opening of .33 cm. was formed (as one representative example).The value of rbf also changed as the table became longer, so that by the end of the century, 1:2.5 ratios were common. By 1800 this value was at 1:2 or smaller.
The date of the development of the rounded tip reed is impossible to establish, although, based upon mouthpiece designs, it can be established before 1780. Both round-tip and square-tip mouthpieces coexisted during this period. In fact, judging from photographic evidence, this situation existed as late as 1800, and so, presumably, did round-tipped and square-tipped reeds.
These early reeds, although mostly made of Arundo donax, were also made of material from the pine tree or fir tree, which must have been very thin in order to compensate for the difference in material properties, (as discussed in chapter four). In any event, they deteriorated easily. Materials such as fishbone, or possibly metal and ivory were also tried.2i
The reed was generally hand-made during this era (mass production began in the middle of the nineteenth century-by 1870, at the latest); however, there were small shops as early as 1770 which produced reeds for commercial consumer u s e .22
The reed was attached to the mouthpiece during this period by means of waxed thread or a silkencord.23 Rings were cut into the mouthpiece to allow for this. The tone was said to have good flexibility and sonority in the lower octave.
We shall see in chapter five why such a situation might be explainable 17
based upon the vibrational characteristics of the reed, and the tendency for the
ligature to act as a high-pass or low-pass filter.
The 2:3 era (1820, about the time of the invention of the metal screw
ligature by Ivan Muller, to 1860) was characterized by an back vamp length about 2/3 that of the front vamp, with the length of the front vamp being about the same as in the 1:3 era. The heel of the 2:3 era reed (see figure 1.10 for an explanation of reed structure terminology) was thinner than modern reeds, and the tip was definitely rounded. The earliest reeds from this era were played with the mouthpiece turned up or down, so that the reed was against either the upper or lower lip. As time went on, the reed down position became standard (it was supported by some players as early as 1784, with about fifty percent of them using the window down position by 1 8 2 4 ).24 The Paris Conservatory adopted the reed down position as standard practice in 1831.25
The variation in the rbf was rather large during this pre-standardization period-from about 2:3.4 for the reeds used on the European continent, to about
2:5.2 for reeds used in England (according to the mouthpieces shown by
Rendall).26 In addition, the width of the reed varied enormously; many of them were still hand-made. The average width was slightly narrower than modern
reeds, 1.2 cm. vs. 1.35 cm. The reed became wider as time progressed, instrument bores changed, and mass production of reeds began, eventually
reaching the modern width for French cut clarinet reeds.
The 1:1 era (1860 to the present) is characterized by a reed having a back vamp and front vamp of about equal length, being slightly wider (1.35 cm.) and 18 thicker at the heel (approximately, 2.5 cm. to 3.5 cm.) than in the 2:3 era (figure
1.3). The tip was rounded, and the playing position was with the mouthpiece turned down.
It is not clear what caused the historical development of a rounded reed tip and mouthpiece (which became universal certainly after about 1820), but the need for the alteration was possibly empirically deduced by manufacturers.
One may describe the rounded part of the reed as a semi-ellipse, whose length
(semi-major axis) is 1.3 cm. and width (semi-minor axis) is .25 cm. This is a tedious composite shape to model for physical calculations (players often modify the shape by hand, anyway) and so an approximation may be useful, which, coincidentally, allows for a natural description of the historical development of the tip, as well. The reed shape may be approximated mathematically by a plane figure known as a supereliipse.27
A superellipse is a generalized form of an ellipse. The formula for an ellipse, the reader may recall, is
(x/a)2 + (y/b)2 = 1 ( 1.1)
where a is the length of the semi-major (long) axis, and b is the length of the semi-minor (short) axis. A superellipse is defined by the formula:
(x/a)2N + (y/b)2N = 1 ( 1.2)
There are several useful limits of the superellipse equation useful in modeling the tip rounding of the clarinet reed. When N =1, the simpie ellipse equation is recovered, so that if the tip were a perfect half ellipse, it couid be 19 described as a superellipse with N = 1 on the half plane. If N = <», then the superellipse degenerates into a rectangle, and describes the case of the 1:3 era reeds, with their rectangular tip. Thus, the 1:3 era reed tip "rounding" may be described as a superelliptical shape with N =°o. For values between 1 and oo, the ellipse becomes gradually more squared (figure 1.4 and figure 1.5).
Based upon empirical measurements, the modern clarinet reed, with its approximately elliptical tip, may be described as a superelliptical shape with
N = 1.786. This value was determined by rewriting equation 1.2 as:
1 2N / xb . 2N b - ( — )
(1.3)
Since this is an implicit equation, N cannot be calculated directly. We rewrite the equation as:
(1.4)
A reasonable “seed’ value of N2 is chosen and from the known values of a, b,
X, and y, a value of Ni is calculated. One continues the iteration until Ng and Ni converge. This is the approximate value of N.
A computer simulation of one-half of a reed tip which uses this value of N is \
—1 - .8 — .6 - .4 " .2 .8 1
Figure 1.4-Clarinet Reed Superellipse Parameter (N) Variation 21 1
.8
A
.2
0 1 .6 0 5 1 N=1 N=2
N=3 N=4
Figure 1.5-Effect of Changing N in the Superellipse Equation (N = 1.78 for Clarinet Reed) 22
shown in figure 1.6. The graphing of only one-half of the reed tip is due to
computational difficulties, as non-integral values of N yield some non-elliptic
regions near -1 on the x axis, and this region has been omitted for clarity. The
profile looks quite close to that of a modern clarinet reed (the scale is arbitrary).
A comparison of the historical shapes mentioned in this chapter, inferred from
available historical mouthpiece designs, is shown in figure 1.3. A comparison
of typical vibration patterns of the first mode of a struck reed withN = ©o and N =
1.786 is given in chapter five.
While it is clear that the evolution of the mouthpiece influenced the
development of the clarinet reed, the influence of changes in the air column on
mouthpiece evolution is poorly understood, and must await a better
understanding of the physical relationship between the two.
Modern Manufacturing Techniques for Clarinet and Saxophone Reeds
Arundo donax is a subtropical to warm/temperate plant, produced commercially for use as musical instrument reeds chiefly in the southeastern
portions of France (figure 1.7) near the Var river, which is seventy-five miles
long, entering the Mediterranean four miles southwest ofN ic e .28 The towns of
Cogolin, Frejus, and Le Lavandou are often mentioned in this regard.29 Other
Mediterranean countries near France also possess a climate suitable for its
cultivation. The plant has been exported to many other regions of the world,
such as India, China, southern Africa, England (although there appear to be
relatively few pockets of the plant left in that country), Spain, the West Indies, 23
0.7
0 6
0 5
0.2
0.1
0.2
Figure 1.6-Computer Superellipse of 1/2 Reed Tip (N = 1.786) 24
Paris
Orleans
Dijon
Limoges
lordeaux (Provence)
Nice
Figure 1.7-The Var Région of Southern France 25
Australia, and the more tropical regions of North America-most notably,
California and the lower fringe of the United States: Texas, Florida, and up the
coast to near Washington D.C.so
Despite the wide geographicai distribution and ecological tolerance of the
plant, the Var region has enjoyed a century-long reputation as the only region
capable of producing high-quality reed material. Neither the nature of French
cane as compared to cane grown in other countries, nor the soil quality nor
growing conditions in the Var region have ever, to the author's knowledge,
been subjected to rigorous scientific studies (excluding possible proprietary
research done by the reed companies themselves). The comparison of quality
between French cane and other national canes, as well as the study of other
agricultural matters, are projects which definitely need to be done in the study of clarinet reeds, but they must be left to those who have the resources available to do so.31
Despite the lack of scientific scrutiny, however, many writers and reed
dealers continue to maintain the exclusivity of the quality of French cane, and
indeed, reed companies often cite the “rich soil and moderate climate” as the
reasons for the quality of their cane in their advertisements.32 Be that as it may, there simply is no evidence available at this time to decide if these claims are justified. In any case, the discussion may be moot, considering Perdue's
prescient remarks on reed research made nearly thirty-five years ago: 26
Any American cane made available at a price and quality competitive with the French product will still have a great psychological disadvantage. A majority of musicians are thoroughly convinced that only cane from France is suitable for their work. This belief can be attributed to the dismal failure of non-French cane as well as the good reputation that French cane has long enjoyed. A careful study of atmospheric and soil conditions under which cane is produced in southeastern France should point the way to the most satisfactory American environment. Such an environment appears to be in the southwestern or western United States.Careful study of the botanical and agronomic characteristics of the plant, in connection with the the detailed study o f the physical and musical quality of the cane, would provide a firm basis on which attempts to establish the industry could be made [italics, mine]. It is questionable whether the industry could profitably support the expense of the necessary research.33
Currently, clarinet and saxophone reeds are the result of a long, tedious, growing, curing, and manufacturing process (figure 1.8) which begins with the planting of the root of the plant-the rhizome (these and other morphological terms which will be described in more detail in the next chapter), typically, in
June.34 It is a myth that Arundo donax grows from seeds, even though they often develop a plume-like structure(panicle) near the top of the stem which is often mistakenly thought to contain seeds.
According to Perdue, these large, very fleshy roots are placed in rows, about two to three meters apart (Vandoren reed company literature places the spacing of the rows at twenty-five feet), and planted about ten centimeters deep (figure
1.8). 35 The plants are watered and hoed as needed (usually, very
rarely), and cultivated very simply-by removing weeds or immature (small diameter) versions of the plant.
The plants develop vertically (botanists cali upward growth, primary growth) for the first year, and then, once achieving full height-about ten to 27 2. Primary 1. Planting Rhizome Internode[ Growth Top Soil t Clyr. Primary Growth / / S i t e s \ ' Node— ^ ÎIÎ!-' Rhizome Primary Thickening / Adventitious Roots
3. Drying Crab 4. Cutting and Stacking
(2-4 months)
(1 yr.to 2yr.) Racks
|5. Splitting and Cutting Quarter Cut :o: Blank
o;
6. Finishing] 7. Shave Vamp and Round Tip (Flatten Bottom)
Figure 1.8-Steps in Reed Manufacturing 28
twenty feet-the cylindrical stem of the plant stops growing upward and begins to thicken outwardly by the addition of new parallel lengthwise (not horizontal)
layers, being allowed to develop, typically, for another year.
The material being added to the thickness of the stem is not properly referred to as "wood", in a botanical sense, since this is reserved for a type of plant material having a different type of 1) cell wall structure and 2) growth pattern than Arundo donax and most other grasses possess. Unlike the grass stem of
Arundo donax, once a true tree has finished its primary or vertical growth phase
(chapter two), it begins to grow outward in a clearly horizontal direction (botanist call this type of growth, secondary growth). This phase is accomplished partially by the addition of new layers of cells which push outward horizontally
(figure 1.9) each new growing season from cells which form a ring, known as a growth ring, or vascular cambium. These growth rings or vascular cambia form anew at the beginning of each season from the position where the growing stopped in the prior season.
The other mechanism by which the expansion of the cells outward is accomplished is by addition of secondary inner walls to the existing primary (or single thickness) cell walls of the already present plant cells as the new cells in the growth ring simultaneously begin to expand outward (figure 1.9).36 The
presence of these secondary walls is what charaterizes true wood cells. Grass cells do not have them.
The thickening whichArundo donax undergoes, by contrast, is not due to the
horizontal outward growth of cells, but, rather, is due to the addition of new Cell Growth Orientation Plasmamembrane (variable size and shape) [simplified ^ee"ce11l Secondary Growth
Primary Primary Growth Cell Vail Direction Secondary Trees and Grasses Cell Vail Cell Growth (Initial (upward) Orientation Nucleus growing phase) ^ olgi Apparatus
Plastid
Primary Thickening Grass Stems Cross-section Plasmamembrane (variable size and shape) (S = Secondary Wall)
Primary Cell Wall(P)
Nucleus Cross-section Golgi Apparatus
Plastid
Cell Wall Simplified Grass Stem Cell Slime Plug Filling a "Leak In a "Food" Conducting Cell
Figure 1.9-A Blomorphologlcal Miscellany 30
parallel vertical layers of cells next to the preexisting vertical layers of cells in the stem formed during primary growth (figure 1.9). This type of outward growth,
derived from vertical additions, is more properly referred to, botanically, as
primary thickening, since it uses the same mechanism as in the primary or vertical growth phase of the plant to achieve its thickening.
This primary thickening reaches one to four centimeters thick in the case of
Arundo donax. This is much less of an increase in thickness than in a true tree of similar initial diameter because of, among other reasons, the lack of secondary cell walls in Arundo donax, which would otherwise result from secondary growth mechanisms, as in true woods. This lack of a secondary wall structure gives Arundo donax less structural support, limiting its buckling strength. This biomechanical limitation is one cause for the smaller diameters and less thickness of the grasses in general.
After two years, the material is han/ested, typically, in winter (December,
January, or February), bundled in groups of twenty stems and placed in an x-shaped configuration called crabs (figure 1.8), which resembles the inner frame of an Indian te p e e .3 7 Once dried, the reeds are stripped of their leaves,cut into four-foot segments, and placed horizontally on low supports to dry in the sun for at least one, and possibly as long as two years.
Given the wide variability in the vibrational responses of manufactured reeds, it is unlikely that the current market pressure for clarinet reeds has allowed a curing schedule that is optimal (forcing the shorter, rather than the longer lengths of time), yet sunning is essential in stabilizing the reed ultrastructure 31 and histochemistry, since during this period chlorophyll, contained in the cell walls, is changed into other chromophores (color producing compounds) which
impart the characteristic golden color of fine c a n e .3 8 The rigidity of the cell walls of the plant (and subsequent reed) likewise stabilizes, being far too pliable for musical use when first harvested.
One point must be emphasized: the material used for woodwind reeds is made from an excised section of a dead plant. Although this point may seem obvious-that the reed material is no longer alive when used for musical purposes, nevertheless this is not trivial from a biostructural viewpoint. The biological and histochemical properties of live and dead plant tissues are quite different from each other. A living plant cell, as an example, has a plasmamembrane (a semi-liquid wall of lipid material inside of the rigid plant cell wall, functioning much as the inner tube in a tire) which hold the fluid-filled contents of the plant cells (figure 1.9). Within these plasmamembranes the plant metabolizes carbon dioxide, excretes wastes, stores nutrients, titrates chemical growth regulators, controls water, respiratory, and nutrient flow, and
participates in a host of other metabolic processes.
When the giant reed plant is harvested for the production of reeds, the cutting of the stems of the plant causes those plasmamembranes closest to the site of laceration to rupture, releasing their contents. This "wounding" of the plant causes an immediate mobilization of biochemical life-saving processes in the plant, such as the formation of sllme-plugs In the food conducting tissue
(similar to the formation of clots in animal injury) which severely alters the 32
original biochemical composition of the plant material (figure 1.9).
Eventually, these severe biochemical processes subside as the slime-plugs
slow down the leakage of material, but what remains for musical use is the
shell of the plant-partially filled with a severely altered histochemical
plasmamembrane environment relative to the original tissue. In time, the
remaining plasmamembranes are drained or evaporated, leaving the form, but
little of the substance, of the original material. It is important, then, to realize in the discussion to follow that the reed material used by musicians is in the final
and relatively fixed stage of a long series of physiological processes occurring
in the plant both before and after harvesting.
Once sun-dried, the stems are processed. The stems (now calledstokes or
batons) are split into quarters by means of a hammer and fluted spike. The quarters are then given a flat bottom. At this stage, the reed is called ablank, and consists of a rectangular slab of reed material. The blank is then precision cut into the shape of the traditional clarinet reed as the final step (figure 1.8),
possibly using diamond-tipped cutting machines, due to the high silica content
of the plant, which would quickly ruin standard stainless-steel blades. The
slope of the reed, as it tapers to the tip, is of paramount importance in the vibrational response of the reed. Different manufacturers have developed
different slope profiles over the years, trying to find the best profile for the widest
number of players.
Many excellent books and articles show the clarinetist how to make a reed
starting with the raw internode (i.e., one tube-like section of the plant), and we 33 have nothing new to add to the procedure, although we shall have much more to say about the final reed shape in chapter five. Rather than summarize the various methods of reed making, we refer the reader to the literature.39
Reed Nomenclature
At this point, it is useful to introduce the nomenclature scheme for the parts of clarinet reed which have become part of the common language of clarinetists, and a separate nomenclature scheme which will be useful in more technical discussions.
A schematic of a clarinet reed is shown in figure 1.10. The clarinetist's terminology for the parts of the reed are given, in part, according to Opperman's terminology.40 As may be seen, the terminology has been derived from a mixture of sources, some more derivative than others. The references to the human body are obvious.
The problem with using this terminology is that, while descriptive of some structural markers of the reed surface, it cannot easily describe with any precision the location of biomorphology and elements within a specific manufactured reed shape. To allow more specificity in the description of the reed surface, an x-y grid in millimeters may be overlaid on the reed surface with the zero vertical line (x axis) passing through the middle of the reed and the zero horizontal line (y axis) passing through the interface between the front and back vamp. We shall always denote the region containing the elliptic tip as one separate subdivision, one coordinate line, T (figure 1.11). 34
—Rounding Point /P oint of Resisting Heart Front Vamp (Vibrating) -Crest (Ridge) i \ Right - Shoulder L e ft------—Fiberous Region Shoulder “ Shoulder Underside ^Stock Back Vamp (Clamped) — Epidermis
Top Viewl \ / iBack View ------Heel (Butt) '------
Front Vamp Back Vamp ^side Profile
Left Edge Side View
Figure 1.10-Common Reed Nomenclature 35
- 4 0 6 (mm) . T Li ne 16 mm rff i------
Epidermal Interface^ 2 mm 0 mm 2 mm
16 mm
Figure 1.11-The Reed Grid 36
Looking down on region T, it is a half-ellipsoid shaped region containing the tip, with a semi-major axis of (typically) 1.3 cm. and a semi-minor axis of .25 cm. The slope (the thickness variation) is very slightly positive (i.e., increasing ), with a rectangular cross-section of slightly increasing width as one proceeds from the initial tip inward to the beginning of the rectangular sides.
The remainder of the front vamp is of complex profile. It is in this region that different reed companies show the greatest variability in manufacturing.
One company (Rico) has a simple rectangular cross-section which is 1.3 cm. in width with a linear increase in thickness along the length of the regions (figure
1.12). Such a "wedge" shaped profile (we shall call it thewedge profile) allows the reed to approximate a gradually thickening beam or plate, and makes the mathematical analysis of its vibration (chapter five) fairly tractable.
The reed is generally reported to require little pressure to initiate vibrations.
Another popular reed shape (Vandoren, Olivieri, Glotin) contains an expanding ridge or crest in the front vamp. This expanding ridge area makes analysis much more complicated due to the variation in a mathematical property known as the radius of gyration, k (which is the moment of inertia,
I, divided by the area function. A, both of which vary along the length of the reed with this shape-more detail on the radius of gyration is given in chapter five).
The cross-sectional geometry of such an expanding ridge profile (we shall refer to it as simply the ridge profile, when this is unambiguous, since there are many possible ridge profiles) may be further divided into four horizontal subregions (approximate values in cm.): 3r, 3rp, 2rg, Ire. as indicated in 37
-1 -2
T ~ )
Cross-section Cross-section
Slope Slope (Thickness) (Thickness)
Figure 1.12-The Wedge Profile 38
figure 1.13, based on variations in structure and thickness (which are responsible for the difficulty in assigning a simple value for k).
3r is the region just beyond region T, and is still dominated by the rectangular cross-section of the T region. In the dynamics of thin beams and plates, the concept that a change in thickness is equivalent to a change in material strength (rigidity), may be important in the thinner portions of this region, since scraping the reed here amounts to large changes in the local bending modulus of the material in this region.
Moving down the reed in region 3r, as the ridge begins to emerge, it does so first by the addition of a small protrusion or "bump" in the middle of the otherwise rectangular cross-section of region 3r to form a compound cross- sectionalshape, which is sufficiently different enough to denote as a separate region: 3rp (i.e., the region 3 centimeters from the front vamp/back vamp interface with rectangular cross-section and a protrusion stacked on top).
Progressing down the reed, the protrusion grows both higher and wider, spreading out beyond half the reed width. At this point the protrusion may no longer be viewed simply as a perturbation of region 3r, as it eventually assumes a size nearly equal in width to the rectangular portion. This is region
2rg, in which a more or less Gaussian-shaped cross-section, which almost reaches the sides of the reed, is attached atop the rectangular cross-section.
The protrusion and the Gaussian cross-sections along with the underlying rectangular base cross-section in the 3rp and 2rg regions, taken together. 3 9
Cross-section
Cross-section
Slope Slope (Thickness) (Thickness)
Figure 1.13-The Expanding Ridge (Crest) Profile 40 comprise the "heart" of the reed.
Finally, in regions 1re and 0, the Gaussian shape extends to the entire width of the reed, and the sides fill out, forming a true half-elliptical cross-section on top of the rectangular cross-section. The thickness of both the rectangular and the elliptical layers continue to increase linearly along the reed length towards the epidermis.
Such an expanded ridge reed profile is generally reported to offer more resistance to the initiation of vibrations than the wedge profile, no doubt due to the added mass of the ridge near the tip (in the 3r subregion), but is also reported to provide more "depth" to the sound.
The amount of variation in the thickness in each of these four regions of sections 0, 1,2, and 3 cm. differs from reed company to reed company, with the
Olivieri company preferring a steeper Gaussian curve in region2^g than either
Vandoren or Glotin (the base rectangular cross-section is thinner in the same regions for the Olivieri shape compared to the other two, with the result that the reed is somewhat more flexible, but also somewhat more sensitive to scraping).
Other theoretical shapes besides the wedge shape or ridge shape are possible in these two regions, although the wedge and the ridge profiles are the two most common shapes. These other shapes may also lead to other simple or complicated subdivisions as well. We shall discuss other theoretical profiles in detail in chapter five.
The back portion of region 2, and all of region 1 (figure 1.11) is a continuation of region 2re, but the thickness has reached its maximum and 41
stabilized. Region 0 (figure 1.11) commonly displays thick-walled fibrous tissue
(called sclerenchyma cells) exposed just under the epidermis. It has a
semielliptical cross-section stacked on a rectangular base, as in regions 10 and
2re. This region, while not placed into direct vibration, does participate in the dissipation of energy through the reed structure, especially at higher frequencies (as we shall show later).
The influences of reed shape on the vibration of the manufactured clarinet
reed, is profound. The influence of the shape on both musical quality and the biophysics of the reed will be studied in detail later.
Rationale of Current Study
Despite the fact that Arundo donax has been the preferred material for the reeds of most orchestral woodwinds for over two-hundred years, a careful scientific study of the materiai properties of the stem (the portion used for clarinet reeds) is still lacking. There have been, to be sure, a number of studies that treat certain aspects of the plant material, but a unified study of the biological, chemical, and engineering properties of this material as it relates directly to the area of musical acoustics is lacking. We shall review the published studies, such as they are, in due course. Most of the remaining
knowledge about the properties of woodwind reed material is anecdotal and of
uneven reliability. This folk wisdom will be assessed in the light of the findings of the current study.
As mentioned earlier, this study cannot include definitive work on the naturally 42
occurring plant Arundo donax, because this would require a substantially more
comprehensive approach to many botanical aspects (such as national
variations in the soil, growth patterns, resulting material properties, etc.) than
befits the context of this work. Rather, the purpose of the current study is to
begin the first large-scale investigation of the biological, chemical, and physical
properties of this plant material in the processed form of the clarinet reed, and to examine some possible types of synthetic replacements.
There are many reasons for undertaking such a study of the processed reed:
1 ) to know the basic engineering parameters of the plant material that is selected and processed as clarinet reeds, 2) to understand reed material degradation over playing time, 3) to measure the reed material variability. Both usable and unusable reeds occur within a random sampling of commercially produced reeds, supposedly of the same strength and constitution, 4) to define the best ranges of the material parameters for use in the manufacture of the clarinet reeds, 5) to correlate these properties with synthetic material substitutes, 6) to test the validity of certain types of folk wisdom concerning reed
use and selection among clarinet players, 7) to study the effects of shaping the
reed (i.e., scraping the reed with a reed knife) on the sound quality and vibrational characteristics of the reed, 8) to obtain a better understanding of how the reed vibrates in the environment of the mouthpiece (the so-called scund-structure Interaction problem), 9) to study the effects of the oral cavity environment on the reed material properties and vibrations.
To address these questions relating to the biology, chemistry, and physics of 43 the processed clarinet reed, a number of different experiments and machine tests are run. Each experiment or experimental machine set-up will be described in detail in the appropriate section following in this document, and the resuiting data collected and analyzed.
As mentioned in point number three above, the reed material exhibits large variations in properties from plant to plant. These variations are often passed on to the processed ciarinet reeds in the form of variable vibration response, water capacity (the abiiity to absorb and retain moisture), and a whole host of other subtle parameter responses. The first goal of this study, therefore, is to measure some of the biological, chemical, and physical parameters of pristine (i.e., reeds taken fresh out of the manufacturer's container) processed clarinet reeds in an attempt to define the range of natural variation within the parameter sets and correlate them with desirabiiity and undesirability (i.e., "good" reeds vs.
"bad" reeds).
In order to study the pristine state of the clarinet reed, a method of obtaining a set of reeds rated in terms of playing quality is needed. One-hundred reeds of different representative brands were given, ten each (i.e., one sealed box of reeds), to ten different students of roughly similar professional or preprofessional ability in the clarinet program at The Ohio State University with the instructions to rate the reeds on a number of different quality and performance criteria, without tampering with the reeds in any way, other than simply playing the reed for some time (however long was needed to make the initial determination of reed quaiity). We call this set of rated reeds, {R}, 44 throughout this document. It will form the basis for much of the material tests to follow.
This study also examines the vibrational characteristics of the clarinet reed which depend upon the natural variations in selected parameters of the pristine reed material. To date, the most complicated model of the clarinet reed developed was by Summerfeldt and Strong, who considered the clarinet reed to be a cantilever beam with linearly varying thickness.4i In reality, this study will show that a detailed analysis of the clarinet reed is best done by considering the reed to be a plate, not a beam, since the material thickness to length ratio is on the order of 1/34 at the tip (a plate has thickness to length ratios usually of 1/20 or less). In fact, a full analysis of the clarinet reed shows it to be a superelliptically-shaped, variable thickness, thin-thick, inhomogeneous plate with moving boundary and load conditions involving sound-structure interaction with the mouthpiece chamber. The reality of the clarinet reed is many orders of magnitude more complex than a simple cantilever beam, and even the situations mentioned above vary as the reed ages. We shall take up each of these topics in turn.
Much of this vibrational analysis will be theoretical in nature using the capabilities of several different computers. The machines will model as realistically as possible the vibration of a typical reed as it is supposed to occur in the mouth of a player. Scraping the reed surface, as many players do, will also be modeled. So as not to be completely devoid of empirical comparisons, the theoretical results will be correlated with stroboscopically slowed video 45 data obtained via fiber optic camera methods of reeds actually being played in the mouth of a skilled musician (the author). In addition, acoustic measurements of the vibrational modes of the reeds in air will be compared with calculated frequencies. It is hoped that such studies will greatly expand the knowledge of how the clarinet reeds function musically.
The second global area of study, and the second goal of this work, is to attempt to ascertain a realistic "playing ecology" of the reed. Reeds are subjected to many different force of a chemical and physical nature during the course of their playing life. By studying the changes in various chemical, physical and biological parameters which occur in the reed as a result of playing, the hope is that the causes of the eventually occurring "reed death" may be more precisely defined. As in the case of the pristine reed, the exact experimental protocols for the study of changes in the different aspects of reed material over time will be presented as warranted.
The results of this study may help to improve the quality of manufactured clarinet reeds, and even help to find a suitable synthetic substitute (although, due to the difficulty of exactly mimicking the complex biological structure of plant cell walls by polymeric formulations, this author doubts that plastic reeds will ever supersede the best natural reeds. Nevertheless, the development of a good substitute, useful, for all but the most demanding acoustical situations may be possible).
It necessary to point out that many of the new results presented in this document must be accepted as provisional. Much of the testing involved only 46
limited samples, due to inevitable economic limitations involved in doing
interdiscipiinary research in no less than nine different, highly specialized fields:
music, chemistry, material science, botany, physics, engineering, medical
pathology, computer science, and optical imaging. Multiple sample tests and
reproducibility studies were, thus, impossible in many cases. It would be of great value to independently confirm the findings presented herein, because they relate substantially to the body of knowledge available to both musicians and scientists. There is already too much pseudoscience in the area of reed research to inflict more upon the reader.
In addition, since much of the research had to be done in areas outside of the author's fields of expertise, important aspects of the research might have been misinterpreted or overlooked. Where possible, the author has solicited expert opinions and help in the testing procedures. Any oversights, omissions, or errors in interpretation are solely the responsibility of the current author. 47
Endnotes
1. Robert E. Purdue, Jr, "Arundo donax--Source of Musical Reeds and Industrial Cellulose," Economic Botany ^2, no.4 (Oct.-Dec. 1958): 375-376.
2. Anthony Baines, Woodwind instruments and Their History (New York: Dover Publications, Inc., 1991); Anthony Baines, Musicai instruments Through the Ages (Middlesex, England: Penguin Books, Ltd., 1976).
3. Perdue, “Arundo...,” 376.
4. F. Geoffrey Rendall, The Clarinet: some notes upon its history and construction^ 3rd ed., revised and with some additional material by Phillip Bates (New York: W.W. Norton and Co., 1971).
5. Most or all of the early single-reed folk instruments used squeaker type excitors.
6. Jack Brymer, The Ciarinet (London: McDonald and Jane's Publishers, Limited, 1976).
7. Nicholas Shackleton, "Clarinet," in The New Groves Dictionary of Musicai instruments, Stanley Sadie, ed. vol. 2 (New York: Grove's Press, 1975): 397.
8. ibid., 397.
9. Perdue, “Arundo...,” 374
10. ibid., 374.
11. Baines, Woodwind Instruments..., plate xxix.
12. Shackleton, “Clarinet...,” 396.
13. Rendall, The C/ar/nef...,56.
14. Another way would be to rebuild some of the old clarinets and attempt to make reeds which match known historical descriptions. This might give a clue as to the exact dimensions which produce the best sounds on the instruments. 48
15. Rendall, The Clarinet.., 6 (upper left mouthpiece)
16. Baines, Woodwindlnstruments..., plate vil (no. 8).
17. ibid., 300.
18. ibid., 300.
19. ibid., 300.
20. Shackleton, “Clarinet...,” 396 (illustration d).
21. Baines, Woodwind Instruments...,30^.
22. Rendall, The Ciarinet...,57.
23. ibid., 8.
24. Shackleton, “Clarinet...,” 397.
25. ibid., 397.
26. Rendall, The Clarinet..., 6.
27. C. M. Wang, L. Wang, and K. M. Liew, "Vibration and Buckling of Superelliptical Plates," Journal of Sound and Vibration 171 no. 3 (1994): 301-314.
28. Webster's New Geographical Dictionary (Springfield, Mass.: Merriam-Webster, 1988): 413, 1285.
29. Rendall, The Ciarinet...,57.49
30. Perdue, “Arundo...,” 370.
31. For instance, the British obois/botanist, Clare Lawton has reported work comparing Australian and French cane (private communication).
32. La Canne a Musique. Vandoren Reed Company brochure: 4; The Making of Greatness. Vandoren Reed Company brochure: 2.
33. Perdue, “Arundo...,” 391.
34. ibid., 380. 49
35. ibid., 381; The Making of Greatness..., 2.
36. A discussion of the morphological and ultrastructural differences between grasses and woods may be found in many standard plant anatomy texts, such as, Katherine Esau, The Anatomy of Seed Plants (New York: John Wiley and Sons, 1977).
37. Perdue, “Arundo...,” 382.
38. Frederick Sack,Lecture Notes, Plant Anatomy 656, The Ohio State University, 1991.
39. Kalmen Opperman, Handbook for Making and Adjusting Single Reeds: for all Clarinets and Saxophones (New York: Chappell and Co., Inc., 1956); a series of three articles by Lee Livengood appear in the pages ofThe Clarinet Magazine : 1 ) Lee Livengood, "A Study of Clarinet Reed Making. Part 1 : a case for clarinet reed making," The Clarinet Magazine 19 no. 3 (May/June 1992), 2) Lee Livengood, "A Study of Clarinet Reed Making. Fait 2: a method for making reed blanks from tube cane,"The Clarinet Magazine 19 no. 4 (July/August 1992), 3) Lee Livengood, "A Study of Clarinet Reed Making. Part 3: selected bibliography," The Clarinet Magazine 20 no. 1 (November/December 1992).
40. ibid., frontispiece
41. Scott D. Sommerfeldt and William J. Strong, “Simulation of a Player-Clarinet System,” Journal of the Acoustical Society of America, 83, no. 5 (May, 1988): 1908- 1917. Chapter II
Arundo donax Anatomy
introduction
The structural elements of theArundo donax plant may be classified according to three natural size ranges: gross (= .1 m-8 m), ultrastructural (=.001 m-.l m), and molecular (<.001 m). This chapter will examine the structural elements of the giant reed plant contained in the first two of these categories.
Issues involving the structure of the plant on the molecular level will be discussed in the context of the histochemistry of the reed (chapter 3).
Gross Anatomv
Morphologically, Arundo donax belongs to the generic botanical family for most grasses-Gramineae (its subfamily \sArundinoideae)J Within
Arundinoideae, the plant is in tribe 12, Festuceae (bamboo, a plant for which clarinet cane is often mistaken, is in another\r\be-Arundinaria ). The genus is Arundo, and the species, donax. A complete biotaxonomic classification is given in figure 2.1. For a listing of the specific traits which comprise each taxon the reader is referred to any standard botany textbook.
The gross anatomy of the giant reed plant, as indeed most grasses, may be
50 51
Arundo donax Classification
Kingdom; Plant I Subkingdom: Embryophta I Phyium: Tracheophyta I Subphylum; Pteropsida I Class; Angiospermae I Order; Monocotyledoneae I Family; Gramineae I Subfamily; Arundinoideae i Tribe (12); Festuceae 1 Genus; Arundo i Species; donax
Figure 2A-Arundo donax taxonomy 52 divided into three distinct functional/structural systems; 1 ) the fool system- responsible for stability of the plant underground, nutrient acquisition, and reproduction, 2) the stem system-responsible for the above-ground structural stability of the plant, and the conduction of water, glucose, and other nutrients, and 3) the leaf system-responsible for photosynthesis, transpiration, and some hydroscopic phenomena. The large-scale anatomy of each of three systems is considered separately.
Figure 2.2 shows several grasses that are structurally related toArundo donax
These specimens were found locally at The Ohio State University. The gross morphological similarities among these particular examples of grasses are quite evident-broad leaves, or plume-like inflorescence, for example, as well as their resemblances to the stem of theArundo donax plant (figure 2.3).
The Root System
The root system of Arundo donax is composed of two major structural elements: 1) the rhizome-a large, fleshy, cylindrical structure, which lies in a predominantly horizontal direction (i.e., perpendicular to the stem direction) just beneath the soil, and from which the stem sprouts, and 2) the well-developed, thin, creeping adventitious roots which extend from the rhizome and reach deep into the soil, allowing the plant to maintain hydration in times of drought by extending down into the water table. The term "adventitious" refers to the development of a structure-roots, in this case-in a location on the plant not normally expected. A photograph of the root system, showing a rhizome, a 53
Figure 2.2-A Sample of Grasses at The Ohio State University 54
Figure 2.2 (cent.)
i 55
Figure 2.2 (cont.) 56
Figure 2.3-The Arundo donax Stem 57
Figure 2.3 (cont.) 58
tangled adventitious root structure, and even an emergent stem Is shown In figure 2.4.
It Is a common misconception that Arundo donax grows from seeds. The reproduction of the plant actually takes place by means of the rhlzome.2 Once planted (two to three meters apart to start within a typical mass-productlon setting, at a depth of about ten centimeters), the rhizome quickly extends adventitious roots and begins to grow an emergent shoot (figure 2.4) that rapidly rises above ground to become a stem. Once the stem begins to grow, the cane Is moved farther ap a rt.3
Typically, new rhizomes are acquired by dividing (cutting up) old rhizomes and replanting them. Occasionally, growers plant large stems sideways underground to acquire rhizomateous matter.4 This last method leads to the development of young plants at the nodes of the stems, which are then transplanted to provide new root systems.
The Stem Svstem
The stem of the giant reed plant Is a long (essentially hollow) tube. The tube, in toto, is usually called a culm. The culm may grow as tall as two to eight meters
(although, about three-five meters Is the average size range of plants used In the production of clarinet or saxophone reeds, judging from commercial photographs obtainable from the reed manufacturer, Vandoren).s
A year old culm of Arundo donax with leaves still attached, 2.77 meters tall, and still In fair condition after harvesting and transport, Is shown In figure 2.5 59
Figure 2.4-The Rhizome. Symbol Key: R-Rhizome, ES-Emergent Shoots 60
Figure 2.4 (cont.) 61 with the author (who Is approximately seventy inches or 1.778 meters tall) standing next to it for comparison. This particular specimen from The Ohio
State University Arboretum has an inner diameter of 1.65 cm. and an outer diameter of 2.35 cm. at its base, yielding a thickness of .7 cm. (figure 2.6).
These sizes are typical for a slightly immature plant, as in this case.
The stem is divided up into smaller cylindrical subunits, called Internodes
(figure 2.7), which are joined together to make up the total length of the stem.
The points at which the internodes are joined, callednodes, are typically regions of a thick-walled, fibrous nature, resembling elbows. There is an alternating N-l-N-l-N-l-N... (N = node, 1= internode) arrangement of the stem parts, as shown in figure 2.7. Typically, according to Perdue, the internode lengths may be between approximately 12 to 30 centimeters.e Measurements on the present specimen indicate the nodes are about one-tenth of those dimensions (1.5 cm. to perhaps 4 cm.).
In addition, the nodal regions are the sites from which leaves sprout. The sites are called leaf gaps, and are holes in the nodes through which the leaf shoots pass (figure 2.8).
In general, the taller the plant, the wider the outer diameter of the stem, which may range from less than 1 cm to 4 cm or more. Since the range of lengths for stems is from two to eight meters, and the range of diameters is from about one to four centimeters, a convenient, "rule-of-thumb" is that:
= Stem Length/Stem Diameter = 200
(2.1) 62
Figure 2.5-The Complete Arundo donax Culm 63
Figure 2.6-Arundo ofonaxCross-section (Stele) 64
Figure 2.7-Arundo donax Intemodes and Nodes. Symbol Key: I - Intemode, N - Node, T -Tannin Deposit 65
Figure 2.8-Nodal Sites for Leaf Generation. Symbol Key: L-Leaf Gap Figure 2.8 (cont.) 66
Intemode
Lee/ Gap
Node ' ■"
Emergent Leaf Intemode 67
Generally, wide diameters are used for larger reed (bass clarinet, etc.). Plants
having diameters in the range of two to three centimeters are usually used for standard Bb clarinet reeds (figure 2.9).
The large size/diameter ratio of thegiant reed plant is explained in terms of the differences in growing patterns between plants classified as trees and grasses. The vertical growth of a plant is termed primary growth, while growth which is horizontal, girthward or outward, which usually occurs in tandem with or after primary growth is finished, is called secondary growth.
True trees typically show both primary growth and secondary growth.
Arundo donax, as well as grasses in general, do not have secondary growth
(there is no seasonal horizontal expansion of the plant), but rather, as the plant grows taller, new parallel vertical layers are added to preexisting layers. This process is called primary thickening, since the thickening of the stem uses only the mechanism of upward (primary) growth. These plants are said to have a primary thickening meristem (a meristem is a site of continuous growth).
The cellular distinctions which allow for secondary growth in trees (via the formation of secondary cell walls), but not in grasses (which have no such inner cell walls ) will be discussed later.
Arundo donax Is a very fast growing stem. A typical growth rate is .3 to .7 mm./week for several months, with the stem being essentially of a mature
(inner) diameter as it grows.7 The primary growth begins once the maximum height is reached. 68
Figure 2.9-The Processed Stem. 69
Figure 2.9 (cont.). Symbol Key: C-Ciarinet Reed (French Cut), B-Bass Clarinet Reed (French Cut) 70
iiliito»
Figure 2.9 (cont.). The Three Tissue System. Symbol Key: T-Tannin, P- Parenchyma, VB-Vascular Tissue, E-Epidermis 71
The Leaf Svstem
The leaves of Arundo donax are two ranked, which means that the leaves grow in simple alternation from side to side along a straight line up the stem
(figure 2.10). The leaves are typically 5 to Scentimeters across at the base, and taper to a tip.
The leaf sheaths typically wrap around the stem, covering it (figure 2.11).
The sheaths may stay attached to the stem long after the leaves have fallen off.
Many times the leave sheath will rot (black spots in figure 2.11), according to
Perdue, discoloring the stem undemeath it (figure 2.7). This causes the brown mottling often seen on the epidermal portion of clarinet reeds, in reality, this discoloration to be due to the presence of tannin, a substance found on the exterior of many plants (see the discussion of the epidermis, below), and Is not the result of a pathological process.3
The inflorescence, or flowering portion of the reed plant, occurs at the tip of the stem, and resembles a plume (figure 2.12). This plume is, in reality, composed of about three to five plum-like bundles which join together to form the larger plume (figure 2.13). Each individual plume bundle is called a panicle.
Each panicle is composed of a grouping of small, three to five millimeter long, V-shaped flowers, resembling wheat stalks, calledspiklets (figure 2.14).
Each spiklet on a panicle is composed of two very small outer leaf-like structures, called glumes (figure 2.15), which enclose another pair of leaves. 72
Figure 2.10-Arundo donax Leaf Pattern (Entire Stem and Close-up) 73
Figure 2.10 (cont.) 74
ti^jr
Figure 2.11-The Leaf Sheath: Black Spots are Areas of Decay on the Leaf Sheath 75
Figure 2.12-Panicles. Symbol Key: P-Panicles 76
Figure 2.13-Panicle and Base Structure Showing Subdivisions of Aggregate 77
Figure 2.13 (cont.)
1
I 78
Figure 2.14-Spiklets 79
Figure 2.15-Splklet (S), Glume (G), and Floret (F) 80
Figure 2.16-Florets 81
Figure 2.17-Perianth. Symbol Key: P-Perlanth, S-Spikiet 82 called florets (figure 2.16). Other more detailed parts of the Inflorescence, such as the perianth (figure 2.17), which are undeveloped In this plant, need not concern us.
Ultrastructure
In the remainder of this document, we shall only be concerned with the stem portion of the reed plant.s This Is not to Imply that the other gross structural elements are not Important to the finished clarinet reed, but a separate study of these elements Is warranted only after the stem characteristics which yield preferable clarinet reeds have been studied and Isolated.
Anatomically, the ultrastructure of the reed stem Is composed of threetissue systems: 1) the dermal, 2) the ground (or supportive), and 3) the vascular
(figure 2 .9 ).io These three tissue types corresponding somewhat loosely to skin, muscle/bone and vein tissue In animals, respectively. Using this classification scheme It Is possible to view the reed stem as an engineering material, and In this context It a three-component material with two of the components Infused and Interlarded (the ground tissue and vascular tissue) while the third component (epidermis) Is layered on top (see figure 2.18).
Dermal Tissue System
The dermal tissue Is contained In theepidermis, the hard outer covering of the reed stem, which Is Initially a greenish color, but Is usually a golden yellow in the mature plant (figure 2.7). The epidermis Is schematically shown In 83
^ p i dermis
************* *************** **************** Vascular Tissue Parenchyma
Figure 2.18-Three-Component Structure of Arundo donaxStem Material 84
figure 2.19. The "shininess" of the surface of the back vamp of the reeds in figure 2.9 is due to a thin layer of wax, which acts as a moisture and pathogen barrier in the living plant. The hardness of the epidermis is due to the unusually high silica content of the outer cells. This silication is shown in the electron dispersive x-ray (EDS) spectrum in figure 2.20, which gives a measurement of the elements present in a sample as it is scanned with a variable energy x-ray or electron beam (this technique is explained in detail in chapter three).
The first spectrum is of the epidermis. The only significant constituent is silicon
(Si). Palladium (Pd) and gold (Au) are coatings placed on the reed sample to allow higher energy electrons to be used, and hence, higher resolution, for the scanning electron microscope. By contrast, the interior cells (figure 2.21) show a much more diverse elemental analysis typical of biochemical processes, where
Chlorine (01), Sodium (Na), Magnesium (Mg), and Calcium (Ca) are most often used in energy transfer mechanisms within the plant.
The discoloration of the reed surface, mentioned earlier, is due to the increased concentration of a tannin, one compound in a whole class of dark- colored (usually brown) fatty acids stored as an energy reserve material for plant metabolism in certain types of cells called tannin cells. The structure of a representative tannin is shown in figure 2.22.
The rotting of the leaves could not be the cause of the brown flecks seen on the epidermis of clarinet reeds, as Perdue suspects, because of the presence of tannin beneath the epidermis, which is seen as thin dark brown lines in 85
Silica Bodies Epiculicuiar Wax Cutin / \
•Wax Pectic - î Material Height
Ceiiuiositic Material (Cell Walls) (Longitudinal - Length Cross-section)
Figure 2.19-Epidermis Schematic 86
C-SU SCfï'MRKl ELECTRON MICROSCCP,' U% i t i 094 m -9 i 15:10 Cursor: 0.200keV = 3
_U_.
0.080 • ."'-L W S ?. 15384 . 3.120 100 • E?IC€P«I£
Figure 2.20-Electron Dispersive X-ray Spectrum of Arundo donaxStem Epidermis. 87
OSLl SCfiM'JING ELECTRON MIO%5COPY LAB TUE 26-JRN-40 05:18 Cursor: 0 000k.eV : 0
11 i
0.000 VF5 : 4096 5.120 m
Figure 2.21-Electron Dispersive X-ray Spectrum oi Arundo donaxStem Inner Tissue. 88
OH OH
Figure 2.22- A Tannin [Catechin] Structure 89 figure 2.9. Since the epidermis is virtually impenetrable, no tannin, if formed by leaf decay, could pass through it into the interior tissue. Neither it is likely that tannin would adhere to the wax cuticle of the epidermis. The tannin discoloration is an indigenous part of the plant cell metabolic process, coming from within the plant as it ages, it exists within the epidermis, not on top of it. It is often thought by clarinetists that better cane has a higher amount of the brownish tannin flecks on the epidermis. This conclusion is debatable
The rigidity of the epidermis is due in part to the silica infusion, and partially to the presence of thin, thick-walled subepldermal sclerenchyma cells found just under the surface of the material (figure 2 . 2 3 ) . Dimensionally, these rod-like cells are 3 to 9 microns thick(1 micron = 1 micrometer = .001 mm.), compared to 1 to 3 microns for soft tissue cells (such asparenchyma, to be discussed later). The inner diameter in a random sampling varies from 4-10 microns (c.f. 50-70 microns for soft tissue cells), while the exterior diameter varies from 7-22 microns (c.f. 50-75 microns for soft tissue cells). Without access to whole stems, it is impossible to estimate the length of these cells, but limited observations from indigenously grown plants indicates that they extend considerable lengths along the stem.
These cells provide enough structural support to allow the giant reed plant to grow to unusually large heights for a grass stem. Sclerenchyma cells began to develop in their embryonic state as water conducting tubes (thexylem, to be discussed momentarily), but at some point in their development specialized into a load-bearing tube, developing thicker walls and smallerpit cells 90
Figure 2.23-Subepideral Sclerencyma Tissue. Symbol Key: E-Epidermis, 8- Sclerencyma 91
Figure 2.23 (cent.). Symbol Key: P-Pit 92
(figure 2.23) than a typical water conducting tube.
Veselac points out a structure in the stem of Arundo donax which she calls
"fiber bands" which seems to be in the same location directly under the
epidermis as the schlerenchyma cells mentioned above, surrounding the stem,
forming an inner band or ring (figure 2.24).12 She also says that the same fibers
surround the nutirient conducting vascular bundles of the plant. So as not to
confuse the reader with what may seem to be differing anatomical terminology
between her study and this one, a bit of explanation is In order.
Sclerenchyma is a generic term for the thick-walled supportive cells
(singularly) or tissue (collectively) of a plant stem. These cells may occur as
long slender tubes, typically called fibers, or as shorter tube-like units, called
sclereids (figure 2.25). Thus, Veselac is making the assumption that the sclerenchyma under the epidermis is essentially composed of fibers. We prefer a more generic term.
To be sure, other types of supportive tissue also exist within the plant, such as the thinner-walled parenchyma cells (figure 2.27), which are the major component of the inner tissue of Arundo donax. When adapted specifically for
load-bearing purposes, such as those parenchyma cells near the epidermis, they may develop cell walls thicker than is typical, and are then said to be
sclerifled.
The "fiber bands" under the epidermis to which Veselac refers are probably a
mixture of sclerifled parenchyma and sclerenchyma. We prefer the more
generic term, subepldermal sclerenchyma (or simply sclerenchyma), to 93
T ib e r Band"
Epidermis
Ground Tissue A: Stem
Xylem Fiber Band"
Metaxylem Pole
Phloem
B: Surrounding Vascular Bundle
-Igure 2.24-Veselac’s Two Locations for Fiber Bands (c.f Figure 2.23 and 2.26) 94
^yietn
^^ppottive)
Pits
'^"'‘<°^^'>fl,lenyKinil,l
2.2s.F,ben ® a w SclersUo 95
refer to them, since there are many types of fibers, such as phioem fibers, xylery fibers, etc., which may be scattered throughout the stem, and the overuse of this term could lead to confusion, especially when the same cells may be labeled by other, less ambiguous n a m e s . 13
Veselac alludes to a second structure (which she also and confusingly calls
"fiber bands") which surrounds the outside ofvascular bundles. These are probably sclerifled parenchyma cells, and not true fibers. It is typical to find paraenchyma cells surrounding vascular bundles in plant stems. To increase their protective ability, they may sometimes develop thicker, sclerifled wails, as do the parenchyma near the epidermis. To avoid confusion, we shall refer to the cells which surround vascular bundles by the generic name, bundle sheath, as they is often called, since the cells "sheath" the vascular bundle, as the name implies (figure 2.26).
Ground Tissue System
The ground or supporting tissue of the Arundo donax stem (c. f. muscle in animal tissue) is composed, essentially, of long chains of one cell type (figure
2.27). These parenchyma cells are typically tetrakaldecahedral in shape, having 14 sides partitioned into one heptagonal face, four hexagonal faces, five pentagonal faces and four square faces (figure 2.28). For a long time it was thought that this shape represents what is known in topology as aminimal surface-one which keeps the volumeas large as possible with the minimum surface area; however, it is known that there are some slight variations 96
m
Figure 2.26-Bundle Sheath. Symbol Key: X-Xylem, Ph-Phloem, B-Bundle Sheath (LIgnlfled), S-Sclerlfled Parenchyma 97
Figure 2.26 (cont.) 98
:..^k.*»>«iw- ;4#^ Mk.## f - . < # Tfcf • * f- •■■•■': ; t
-.Hir'KS^irar'iS?
K % : r % V.Va=cu,ar 99
Figure 2.27 (cont.) 100
Figure 2.27 (cont.). Transverse Section.
^ 101
Figure 2.27 (cont.). Transverse Section. Symbol Key; P-Parenchyma Cell, L- Lignin, W-Cell Wall 102
Figure 2.28-Parenchyma Topology 103
statistically from this idea condition in plant stems. 1 <
Dimensionally, approximating the parenchyma cell as a parallelpiped induces only a small error. The length in a random sample varied from 85.44 to
126.75 microns (pm), with a variation in the "width" of 50 to70 pm. These more accurate measurements were conducted real-time on a specially adapted JOEL scanning electron microscope (SEM) with a computer-controlled digital micrometer, while the other values were obtained from ruler measurements of
SEM micrographs. The cell walls are typically 1 to 3 pm thick (2.6 pm, for a typical example, measured by SEM).
As a tissue, parenchyma occurs in long stacked sheets which do not maintain exact alignment of the cell wall orientations or lengths from sheet to sheet
(figure 2.29). In many ways this stacked sheet arrangement gives the ground tissue, which is very simple in structure (almost a girder network), a unit crystal morphology (figure 2.30). To a first approximation the ground tissue may be modeled as an extended imperfect lattice, such as one might see in a crystal.
This crystalline-like structuring (normal wood is much more amorphous in the internal structure of the ground tissue), in some ways makesArundo donax easier to model as a vibrating entity than wood.
The unit cells (parenchyma cells) of this quasi-crystalline ground tissue are either hollow or filled with a gummy protective substance called lignin (figure
2.27), and because of the simple, nearly regular ordering pattern of these hollow/filled unit cells, we suspect that energy is much more efficiently dissipated throughout the ground tissue ofArundo donax than in more 104
Figure 2.29-Parenchyma “Sheet” 105
i l l H
Figure 2.30-Parenchyma Tissue Unit Crystal Approximation 106
amorphously structured wood ground tissue. This efficiently is likely one
reason for the unusually high damping coefficient of Arundo donax (more than ten times that of wood)--the energy resulting from an impulse applied to the
ground tissue is siphoned away from the initial site of impulse at a very high
rate. This has enormous implications for musical tone generation as we shall see.
As an aside, lignin is a highly complex molecule (there are many varieties of
lignins, as discussed in the next chapter), formed from dead cells, which acts as an all-purpose filler substance in stems, gives water protection to vulnerable cells, acts as a pathogen barrier, a parasite growth inhibitor, etc. It is
hydrophobic (water repelling), and tends to shrink and stabilize the cell wall thickness of the parenchyma cells because less water is able to penetrate them.15 The older the section of the plant, the more likely lignin is to be found as the cells become more brittle and more in need of reinforcing.
Because of its large molecular shape and extended polymeric formulation, lignin is a very viscous type of material. The cell walls of the parenchyma cells, by contrast, are essentially elastic, giving the reed a "springiness". The vascular tissue, to be discussed next, is somewhere in-between a viscous and an elastic material (it is usually classified as a viscous material). It is customary to refer to a material having a combination of resistive and elastic components as a viscoelastic material. We shall discuss these mechanical terms in the next two chapters. 107
Vascular Tissue System
Interspersed In the matrix of ground tissue (figure 2.27) are both the food and water conducting (vascular) cells of the plant, which are long tube-llke structures. These two distinct types of vascular cells or tissue do not usually occur In Isolation, but typically together in distinct collections of vascular tissue
(called, vascular bundles) which are Incorporated into the ground tissue as shown In figures 2.26 and 2.31. Vascular bundles In the Interior of the stem average from 250 to 300 p,m In diameter, while those near the epidermis average from 50 to 100 pm.
The arrangement of vascular tissue within the ground tissue of a stem varies from plant type to plant type, and one often refers to the collection of the supportive and vascular tissue In a stem as astele, from the German word meaning stem. There are many different types of stele arrangements, and several of these arrangements are shown In figure 2.32. InArundo donax, the vascular bundles are scatter randomly throughout the stem, giving this plant the designation of an atactostele.
As one progresses from the Interior tissue towards the epidermis, the number of vascular bundles Increase according to some power law (figure 2.33):
Nvb = No (R/Rinner )^ (2.2)
where No is the number of vascular bundles along the Inner radius encompassing the annulus, Rjnner + Rvascuiar Bundle- Rinner Is the inner radius, R Is 108
Figure 2.31-Vascular Bundle. Symbol Key: PX-Protoxylem, MX-Metaxylem, PP- Protophloem, MP-Metaphloem, PO-Metaxylem Pole, P-Parenchyma, B-Bundle Sheath 109
Figure 2.31 (cent.) 110
Black = Vascular Tissue Whit e = Gro un d Tiss u e AtactostelefA'undo donax)
Subcaiagories Cross-section Protest el 8 (No Ground Tissue): \/^Halptostele Siphonostele: ( Actinostele Ectophloic 'x V . Plectostele O Miphiphlolc J
Subcatagories Subcatagories
\ Siphonostele: r Dictyostele Eustele V (Amphlphloic)
3-d1mens1ona1 example: Siphonostele
O
Figure 2.32-Various Steles 111
outer
Inner
+ R inner YB
There is an increase in the number of vascular bundles as one moves from the inner radius to the outer radius which is governed by a power lav of theform: Nvb (vb/mm) inner
R inner '^oiier
Figure 2.33-An Explanation of the Vascular Bundle Power Law 112 the radius of interest (Router ^ R ^ Rinner). Router is the outer radius, and P is an
exponential (power law) scaling factor. From emeprical measurements, No is typically on the order of 4 bundles/cm. and P is typically on the order of 1.96.
The xyiem (figure 2.34) is the name for water conducting tubes (composed of smaller tube-like subunits calledtrachiery elements joined end to end) which occurs in the vascular bundle, and the phloem (figure 2.35) is the food conducting tube (composed of smaller sieve tube elements, similarly linked together).
Xylem have diameters of 50 to 100 pm in the inner portion of the stem, and 20 to 40 pm near the epidermis. Phloem has very irregular cell construction, which makes diameter measurements difficult, however, an approximate range of 5 to
20 pm may be given. The length of each sieve tube ranges from 150 to 250 pm.
The particular arrangement of the vascular tissue (xylem and phloem) in a vascular bundle is one type of distinguishing characteristic of a plant. The type iorArundo donax is known as acollateral arrangement (figure 2.31 and figure
2.36). The phloem region lies above the xylem region separated by an imaginary line (hence the designation collateral) running between them. The phloem region is abaxial relative to the xylem. The term abaxial signifies that the phloem is closer to the epidermis or surface than the xylem region. The cells sandwiched between the xylem and phloem are the parenchyma type cells mentioned above.
In discussing the development of a typical vascular bundle, the imaginary collateral line is a useful structural device. It corresponds to a region of 113
Figure 2.34-Xylem Cells. Symbol Key: X-Xylem Cell (Tracheid), P-Pit, W-Cell Wall 114
Figure 2.34 (cent.). Transverse Section. 115
i
Figure 2.35-Phloem Cells. Symbol Key: P-Phloem Cells, C-Companlon Cells 116
Figure 2.35 (cent.). Longitudinal Section. 117
Bundle Sheath X Old (EaMy)-'Proto- Protophloem
Metaphloem
Ph oem- Imaginary New="Meta- Collateral ■ ■ "L in e g Xyem
Metaxylem Old (Early) ="Proto Metaxylem Pole
Protoxylem
In a typical vascular bundle, the food c on ductin g tiss u e (phloem) lies above an imaginary canter(collateral) line, when seen in this orientation. Thewaterconducting tissue (xylem) lies belowtheiine. Earlier tissue is pushed away from the coliateral (meristematic) line, so that the earliest (proto) tissueisnearthe outside of the bundle,andthe younger(meta) tissue is nearerthe center.
Figure 2.36-An Explanation of the Collateral Arrangement of Cells In the Vascular Bundles of Arundo donax 118
generation where xylem is forming and pushed away below the line, and phloem is formed and pushed away above of the line. Starting from the imaginary dividing line, the first phloem to develop (protophloem or "first" phloem) is pushed away from the center line as later(metaphloem or "middle" phloem) cells develop. Thus, the vascular bundle elements are older the farther away they are from the collateral line. The designations proto- and meta- simply refer to whether the phloem developed at the beginning of the life of the vascular bundle or later on, respectively. The same situation occurs for the xyiem, leading to the designations, protoxylem and metaxylem. The result is show schematically in figure 2.36.
As the growth stresses of the developing vascular bundle push the early cells farther and farther away from the collateral line, they begin to impact against the outer circular region of thick lignified parenchyma cells(bundle sheath) which encases the vascular bundle (figure 2.36). The forces are so great that often the earliest phloem and xylem are crushed up against the two half-walls of the vascular bundle.
Typically, the xylem in the vascular bundles are surrounded by smaller, immature, and somewhat thicker types of tissue which resemble xylem in appearance (figures 2.37 and 2.25). These tissues surrounding the xylem are called xylem fibers (or simply fibers) and provide support and protection for the xylem. The phloem tubes occasionally have such support as well, but it is more characteristic to find small phloem-likecompanion cells coupled to the phloem cells to form a phloem/companion cell pair (figure 2.38). 119
Figure 2.37-Xylem Fiber 120
r ,
n KV X 2 I
Figure 2.38-Companlon Cells 121
Standing often at one apex of a triangle formed by the two metaxylae in a
vascular bundle is the smaller metaxylem pole ( typically, 65% the size of
the xylem size in the vascular bundle-figure 2.31). This lacuna is generally
nonfunctioning.
The near-epidermal vascular bundles tend to be smaller (typically 1/3 to 1/5
as large) than those lying in the interior of the stem and have some elongation
of the abaxial side of the bundles, giving them an egg-shaped appearance
(figure 2.31).
It is an interesting fact that xylem tissue actually kills itself shortly after
reaching maturity so as to be useful in water conduction (only the shell is
important). This often precipitates the formation of lignin around it. Phloem cells engage in energy transfer and storage within the plant, and must remain alive, so there exists the odd case of the functioning xylem being dead and the functioning phloem being alive.
From the standpoints of physical stress-strain properties, water retention, and its eventual breakdown as a viable vibrational medium, it is important to mention two other anatomical elements of the vascular tissue, specifically elements of the xylem tubes. The first are small (1 p,m by 2 pm) ellipsoidal perforations, called pits (figure 2.39), that iie along the outside of the xyiem tubes and allow materials such as proteins, ions, etc., to be pumped into (or out of) the xylem tube in order to be transported upstream or downstream via the streaming fluids inside of the tube. These pits align themselves in a helical pattern (called helical thickening). A typical coil of the helix is 6.3 pm 122
% I I
Figure 2.39-Pits 123
Figure 2.40-Helical Thickening 124 thick. A scanning electron micrograph of an exposed helical section of a xylem tube if shown in figure 2.40. The helical thickening strengthens the xylem cell, much as a spring mounted inside of a tube of cloth might.
Cell walls
Each cell of the reed, when alive, is filled with a complex fluid ( called the plasmamembrane) that provides a hydrostatic pressure inside the membrane and pushes outward against the rigid cell wall that contains it. This turgor pressure is very much like the function of air pressure inside of an inner tube-providing support and shock resistance (figure 2.41).
This turgor pressure requires the development of thick cellulositic cell walls capable of resisting the immense hydrostatic pressures of the plasmamembranes. In the case ofArundo donax, as in most grass stems which have only primary growth, these cell walls may be separated into two parts, having approximately a 2:1 ratio in thickness: the part common between and connecting any two adjacent cells-the middle lammela, ( .875 pm) and the part which beiongs exclusively to the individual wall of a cell, the primary wall
( 1.75 pm), as shown in figure 2.42. The chemistry changes radically from the middle lammela to the primary wall-a point we shall return to in the next chaper.
Arundo donax is a grass stem, and as such, lacks some of the other major components of typical wood cell walls. Chief among the missing elements is a secondary wall which forms interior to the primary wall, and is responsible for 125
Cell Wall
"VSÿ "Deflated" plasmamembrane (small pressure y against cell wails)
Lov
Turgor Press I High
Inflated plasmamembrane Ê (large pressure against cell wails)
Figure 2.41-An Explanation of Turgor Pressure .126
0002 20K0- X
Figure 2.42-The Cell Wall. Symbol List: P-Primary Wall, M-Middle Lamella, L- Lacuna 127
the horizontal thickening of most trees. BecauseArundo donax lacks this secondary cell wall structure, it characteristically grows very tall but not very wide.
The fact that Arundo donax grows slightly thicker horizontally than most grasses is because of a horizontal growing region(primary thickening meristem) in the outermost portion of the internodes which resembles in some respects the so-called secondary (or horizontal as opposed to primary or horizontal) thickening found in normal woods. Although most xylem cells with secondary cell walls have pits, some prior researchers ofArundo donax have mistaken the existence of pits inArundo donax xylem as evidence of secondary cell walls. In fact there is more than one kind of pit and some of the simpler types of pits (so-called simple pits, which are the type found in Arundo donax) are quite often found in cells having only primary walls.
At an even smaller level, these cell walls are composed of long, layered chains of cellulose called fibrils with an alteration of crystallite regions and relatively amorphous regions within a fibril (figure 2 .4 3 ) .16 These fibrils form a network of cellulose into which a number of other chemical substances are interlarded, as we shall discuss in the next chapter.
Before we turn to a discussion of the basic chemical components of the clarinet reed, all of which exist solely in the plant cell walls since the plasmamembranes are dried out during processing, we summarize this section of anatomy by showing the relative sizes of the different anatomical components mentioned in this section (chart one). 128
Middle Lamella Primary Wall
lary
FIbrila
Magnified
Elementary Fibril
Magnified VfW {«VVLV.------/C e llu lo s e Polymer m > Lattice
Amorphous Cellulose
Figure 2.43-The Fibril Concept 129
Table 2.1-Comparative Size of Arundo donax Cells and Their Components
Element Size Comparative Size illustration
Stem 2-8 M 20,000 X larger than xyletn
Leaves 5 -8 cm 40 xsmalierthan the stem
Parenchyma 80-130(ji lO x less volume than length xyiem cells 50-70|a radius
150-250 n Xylem Approximately the length thickness of human hair 20 -100 [A radius
150-250 n Phloem 1/4 the thickness of length human hair 5-20n radius
Sclerenchyma 7-22JX 1/4 the radius of xyiem, radius yet 3 xthickerthan xyiem
Fibril < .Oln > 200,000 xsmalierthan stem 130
Endnotes
1. Purdue, Arundo donax...page 368.
2. ibid., page 381; the author gratefully acknowledges the help of Richard Pearsonin obtaining this specimen.
3. ibid., page 381.
4. ibid., page 380.
5. Vandoren Reed Co., The Making of Greatness... page
6. Purdue, Arundo donax...page 369.
7. ibid., page 369.
8. It seems strange that Purdue, an experience botanist, would make this assertion, when a partial understanding of plant flavinoids (tannin, for example) already in existed before his article was written.
9. For a thorough discussion of all of the aspects of plant ultrastructure, the author can do no better than to recommend, Esau, The Anatomy of Seed Plants...
10. Fredrick Sack, Lecture Notes, Plant Anatomy, 656...; tissue is defined here as a large collection of cells which function as a unit.
11. The author is grateful to Fredrick Sack for a discussion about proper nomenclature for these cells, as there is some confusion in the reed literature.
12. Veselac, A Companson...page 34
13. This terminological ambiguity has been the source of numerous arguments between researchers in the reed field.
14. See Esau, The Anatomy of Seed Plants...tor a discussion of parenchyma morphology. 131
15. Fengel, Dietrich, and Wegener, Gerd. Wood: chemistry, ultrastructure, reactions (New York: Waiter de Gruyter, 1984): chapter 6.
16. Wegener and Fengel,Wood, page 97. Chapter III
Clarinet Reed Chemistry
The Chemistry of Arundo donax
As mentioned in chapter one, a clarinet reed is nothing more than the shell or
remnant of cell walls of the giant reed plant after the plasmamembranes have
been removed due to cutting, curing, and shaping. The manufacturing process
leaves the basic cell wall “building blocks” of the clarinet reed intact in a
relatively fixed form so that the entire chemistry of clarinet reed material is contained within them (figure 2.42). We shall be concerned primarily in this chapter with the molecular composition within the cell wall lattice structure, as this forms the basis for many of the engineering properties of the clarinet reed material.
Elemental Analysis
Electron dispersive x-ray analysis may be used to study the elemental composition of a material in a qualitative manner. This method takes its idea from the studies of the early twentieth-century physicist, H. G. J. Moseley, who found (1913) that when an element is bombarded by energetic electrons inner shell electrons may be dislodged from the atom, radiating x-rays of a frequency
132 133 particular to that element according to the formula:
3cR
(3.1) where c is the speed of light, R is the Rydberg constant, and Z is the atomic number of the element."!
If such high energy electrons (on the order of 20,000 electron volts) are directed at the surface of material composed of a single unknown element the surface will radiate x-rays whose frequency uniquely identifies the element.
Typically, one starts with some low energy of electrons and slowly increases the energy until a maximum transmitted radiation is found. One may then identify the element by its characteristic frequency, since these have been precisely determined (in fact, Moseley’s method was used to confirm the discovery of new elements after about 1930). In practice, since energy and frequency are related by the Plank relationship (E = hF , where, h = Plank’s constant), typically most
EDS-capable machines vary the energy of the incident electron beam, and then calculates the frequency from the known energy of the beam. For a composite material, one finds a series of peaks in the x-ray spectrum, each peak being characteristic for one of the elements in the sample.
Figure (2.20) shows a typical EDS analysis from the epidermis of a clarinet reed. The high silica (SiOa) content is reflected by the very large peak in silicon
(Si) present in the spectrum. The palladium (Pd) and gold (Au) peaks are artifacts of their use as coating agents to allow the sample to withstand the high 134 energy electron bombardment without deterioration.
By contrast, the interior cells (figure 2.21) show a much more diverse elemental analysis, typical of organic and bio-organic compounds: carbon, hydrogen, and oxygen (the basic building blocks of organic chemistry and biochemistry), as well as chlorine (Cl), sodium (Na), magnesium (Mg), and calcium (Ca), which are the most often used elements in energy transfer mechanisms within a plant.
This technique is not generally quantitative (although some systems will allow for semi-quantitative analysis), but does indicate that the interior of the plant has most of the general elemental characteristics of a (once) living biological material, whereas the epidermis is more closely related to a glass-like inorganic material in composition.
Despite the fact that there are hundreds or thousands of compounds which may be synthesized by the living reed plant from only the elements mentioned above, to a large extent there are only three major organic chemical compounds found in the reed cell walls after the plasmamebranes are removed.
Two of these compounds are carbohydrates, and one is a phenolic derivative.
Each of these three compounds will be discussed in turn.
Cellulose
The first and most important of the compounds contained in the cell walls of
Arundo donax is cellulose, which, according to Fengel and Wegener, comprises 40%-50% of the total plant material for bamboo. This is 135
approximately the same percentage for Arundo donax, according to Perdue.s
Celluiose is the name given to a six-member ring structure of carbon and oxygen (cellulose therefore belongs to the branched hexose or pyranose family
of carbohydrates). Its technical name is p-d-glucopyranose (figure 3.1):
OH
H OH
Figure 3.1-|3-d-glucopyranose
Cellulose is rarely found as a single carbon ring, but rather, is usually found in a paired arrangement with another p-d-glucopyranose ring connected by an oxygen bridge (as shown in figure 3.2):
HH OH OH
OH
Figure 3.2-Celiobiose
This oxygen bridge (the formation of oxygen bridges is one thing which renders carbohydrate chemistry unique), incidentally, is what renders cellulose 136
indigestible to mammals. Glucose, the most common simple sugar, differs from
cellulose only in the position of this oxygen bride.
Numbering the carbon atoms on the two rings with the aldehyde containing
carbon (i.e., the carbon to the left of the oxygen as seen from outside the ring)
always numbered one, this linkage is between the 1 carbon of ring 1 and the 4
carbon of ring 2.3 The designation 1->4 is often used to denote where the
carbon “trusses” of the bridge are in the joined rings (figure 3.3):
CH2OH H OH
OH H OH H
H OH CH-OH
Figure 3.3-1—>4 (3-d-glucopyranose Bridge Structure
Thus, this is a 1-->4 p-d-glucopyranose bridge structure. This two molecule version of cellulose has a special name:cellobiose.
These cellobiose units link together into long continuous chains (the oxygen bridge alternates in the up and down position). If cellulose is called a monomer (literally, “mono = one, mer” = unit, in Latin), and cellobiose is a dimer (i.e., two unit), then extended chains of cellulose molecules are known as polymers: 137
H Q1 H m M « H «
Figure 3.4-Celluiose Polymer Structure
The most common polymeric form of cellulose in woods is cellulose I (there are four major forms of cellulose, and several subcategories). Large-scale order is generated not only by the stringing together of cellulose molecules in a line (forming a linear polymer), but also because some of the hydrogen atoms on one ring of a cellulose molecule can weakly bond across space to other hydrogen atoms on another ring (so-called, hydrogen bonding). This hydrogen bonding (there is bonding both within a cellobiose molecule.
Intramolecular hydrogen bonding, and across space between other cellobiose molecules, intermolecular hydrogen bonding) allows bonding between the cellulose molecules in a three-dimensional sense, which permits cellulose macromolecules to conserve energy and space by arranging themselves along the sides of a cubic-like arrangement, called monoclinic a unit cell (figure 3.5).6
In the monoclinic unit cell, the three vertices, a, b, c are of different lengths, and the three angles between them, a, p, y are related by a = (hence the term, monoclinic, which means “single angle", referring to the single nonequal angle). Each unit cell structure is a single unit in the three-dimensional lattice of the extended hydrogen bonded polymer chains (figure 2.43). These extended 138
Hydrogen Bond nonoclinic Uni t Arrangement of £*JJ______Celiufose Atom* 002 020r 200 ' X /
...... %
Miller Indieies for Cellulose Unit Crystal Lattice
Figure 3.5-Cellulose Crystal Structure 139
lattice chains grow into a macromolecular structure which resembles thin fibers
-- elementary fibrils. These elementary fibrils, in turn, form the fibrils
mentioned in chapter two, which then fuse together to form the ceil walls of the
plant.
There are different planes which pass through the monoclinic cell, and they
are identified by a set of indices called Miller indices. The origin of the
indices is not hard to see in figure 3.5. A point (usually a corner) on the unit cell
is assigned as an arbitrary zero point (0,0,0) for the cell in the x, y, and z
directions. The planes passing from the origin to the points on the cell are
noted. In the monoclinic unit celi, there is one plane, for instance which passes
through the cell exactly at the midpoint of the c vertex (c = 1/2). Since it does
not intersect the a orb axis, one is free to give these coordinates any vaiue, and
they are typically assigned to infinity (o o ). This particular plane of the monclinic
unit cell intersects the iattice at 0,0,0 and (o°,1/2,oo)v The Miller indices are
generated by taking the reciprocal of the point on the unit cell other than the origin which intersects the plane, in this case,( 1/o o , 2, 1 /o o ) = (0,2,0). This plane
is designated then the 020 plane, and it is the major plane in cellulose. Since the unit cell has symmetry, the planes 020, 002, and 200 are equivalent. The
major planes are shown in figure 3.5.
When an x-ray beam, which has a wavelength on the order of the spacing
between edges of the unit cell for a given substance impacts with the unit cell, depending upon the size and shape of the unit cell (there are fourteen different types of three-dimensional unit cells, the so-called Bravais Lattices), the 140 x-rays are scattered at characteristic angles off of the different planes of the unit cell.7
An x-ray diffractogram of a clarinet reed is shown in figure 3.6. This diffractogram (henceforth, this method of obtaining the x-ray diffraction information will be abbreviated as XRD) is made by placing a portion of the clarinet reed in a flat holder and mounting it on a rotating turret. A fixed x-ray beam, using a Ca ka radiation source is then shined at the holder as the holder is slowly rotated about 360 degrees. Depending upon how the molecules are oriented to the beam, scattering occurs when the x-ray beam impacts a natural plane of the unit cell and the intensity of the reflected x-ray beam is recorded by use of a scintillation counter as counts per unit time-in this case, ten seconds.
We shall represent this quantity as counts/10 sec. or cts, for short. The angle of rotation of the holder at that point tells at what angle that particular natural plane is found in the unit cell.
The large peak in the diffractogram occurs at 22.2 o. This is the principle scattering angle for the 020 plane of the cellulose unit cell. There are two smaller “halos”, the doublet at 16.0° and 17.6o and the singlet at 38.4o, which are the 101 (1 0 1 ) and the 040 planes respectively (the underscoring indicates an axis perpendicular to the other axis).
A knowledge of these angles may allow one to reconstruct the unit cell fairly well, however, a better method to determine the unit cell parameters of cellulose
( the angles and the lengths of the cell) is the single crystal method, in which a small single crystal of the cellulose material is exposed to an x-ray beam for 141
Figure 3.6-X-ray Detraction Spectrum of Clarinet Reed 142 extended periods at different rotation angles and the diffraction pattern is recorded on photographic film. Such detailed methods were not available for this study, however, and the bulk or powder x-ray (XRD) method mentioned above was used.
Degree of Crvstallization bv XRD
The cellulose matrix is only partially ordered (the monoclinic extended lattice). Some of the cellulose molecules are not bonded in this matrix, but exist as collections of individual molecules which tend to be amorphous in structure.
These amorphous regions exist in combination with the crystalline cellulose
(figure 2.43). The amount of ordered cellulose (0% to 100%) relative to the total amount of cellulose is reflected by a quantity known as thedegree of crystallization (or crystallinity index), which we shall write as, “ %C ”. In other words, the degree of crystallization measures the percentage of the cellulose which belongs to the ordered monoclinic lattice network.
There are two methods which are used to determine this quantity. The first method uses the intensity of the 020 line of the XRD spectrogram. The second method uses selected absorption intensities of bands in the infrared spectrum.
The infrared method tends to overestimate the %C, but is easier to obtain.
In the XRD method, the intensity of the 020 peak is taken to be a measure of the amount of crystallized material trapped in the extended monoclinic cell structure.8 Since some of the cellulose molecules are not bonded in this matrix, it is assumed that this amorphous cellulose forms a background noise in the 143 spectrum. The %C is calculated by subtracting the 020 intensity from the amorphous background and taking the ratio according to the formula:
% C = [ lo20"lam /lo20 ] X 100% (3.2)
A place in the spectrogram which is not influenced by the monoclinic lattice is used as a reference for the amorphous background intensity. Most often, this value is 19°.
A typicai calculation of the %C proceeds as foilows: the maximum intensity of the 020 is seen to be 992 counts/10 sec. at 22.053°. The amorphous background intensity is 290 at 19°. Subtracting the amorphous intensity from the 020 intensity and taking the ratio gives:
992 cts.-290 cts
%C = ______X 100% = 70.8% (3.3)
992 cts
This %C value is common for piant cellulose, which varies between 60% to
80%.
As an experiment, we selected three pristine reeds (reeds taken out of an unopened box of Vandoren V I2 reeds, strength 3 1/2), and four spent reeds
(supplied by students and faculty), and obtained spectrograms of each, centering on the theta values encompassing the 020 peak. The %C values given in table 3.1 were obtained by two slightly different methods, which use: 1) maximum intensity measurements, 2) intensity measurements at a fixed point in 144
R eed Label lnt.22.2G Max. Int. Amoro. Int. %C (22.20) %C(Max. IP 984 984 290 70.528 7 0 .5 2 8 2P 863 889 286 66.859 67.829 3P 959 963 2 9 3 69.447 6 9 .5 7 4 IS 1055 1077 3 5 4 66.445 67.130 2 8 979 1008 343 64.964 65.972 3 8 1058 1076 3 6 7 65.311 65.892 4 8 867 868 295 65.974 6 6 .0 1 3
1P 2P 3P 1S 2S 3S 4S
Reed Label
Table 3.1-%C Data for Pristine and Spent Reeds 145 the 020 peak (22.2°). The results are essentially the same (although pristine
reed two is shifted to a higher %C value). A superimposed plot of the spectrograms are presented in figure 3.7. The label p stands for “pristine” and the label s stands for, “spent.”
Several things are worthy of note. The %C values of the pristine reeds
(average, %C of 69.6%) are slightly higher than the %C for spent reeds
(average, %C of 66%). Also, the pristine reed maxima are shifted on average to lower theta values (22.05 vs. 22.2) relative to the spent reeds, indicating a larger lattice spacing, 4.027 Angstroms vs. 4.00 Angstroms The normally reported values for the lattice spacing of the 002 to 002 planes in the unit cell is approximately double these values (7.9 Angstroms is the value usually reported) because the measurements indicated here are for only half length, i.e., the distance of the 002 to 020 axis, instead of 002 to 002 axis (which is the complete span of the unit cell).
The lower %C values of spent reeds may be explained in a number of ways.
The first possible explanation is that the cellulose extended lattice of a spent reed breaks up into slightly smaller units than that found in a pristine reed due to vibrational stresses on the reed cell walls. This hypothesis would be in line with findings pointed out by Carleen Hutchin that violin wood tends to decrystallize over time due to vibrations of the violin body as the instrument is played, s
Another, more chemically-based explanation is decreased hydrogen bonding in the interlattice matrix. As we have seen, it is hydrogen bonding 146
R I
- Ri
n
(spuBsnoqj_) SpuODBS 01 Sfunoj
Figure 3.7-Superimposed 020 Peaks for Spent and Pristine Reeds 147
which gives cellulose its supermolecular lattice structure, and we shall shortly
present evidence that a class of compounds called hemlcelluloses are
removed from the reed cell wall over time due to saliva. Hemicelluloses tend to
hydrogen bond to the exterior of the cellulose lattice forming a parallel sheet to
it. This hemicellulose sheet allows water to get trapped between itself and the
cellulose lattice. The combined hydrogen bonding of both the hemicelluloses
and the water to the cellulose matrix increases the apparent crystallization of the cellulose matrix. When the hemicelluloses are removed, one of these two hydrogen bond sources (hemicelluloses) is removed (water continues to bond to the cellulose material), and the lattice shrinks, fractures or holes appear, lowering the order in the cellulose extended matrix.
A third possible explanation is that the results are somehow artifactual. The reed must be placed in a holder, and if the reed is not placed in precisely the same spot each time, the reed, being a wedge as opposed to a flat plate, will then allow varying degrees of material thickness to be exposed to the x-ray beam, which could influence the intensity of the beam which is diffracted, and possibly the resulting %C, however, since it is the ratio of crystalline to amorphous peak intensities which yield the %C, both peaks should be influenced by the positioning of the reed to approximately the same extent, cancelling the effect of thickness changes, leaving the ratio unchanged.
It seems, then, that this small, but measurable decrystallization effect is real.
The data presented, while limited, is provocative, and warrants a more detailed study with larger sample numbers. Nevertheless, spent clarinet reeds appear to 148 decrystallize slightly, perhaps due to vibrationally induced stresses or the loss of hemicellulose in the cell wall matrix. The lattice spacing also appears to be decrease slightly, which suggests a contraction of the cellulose matrix after
removal of the hemicellulose.
Decree of Crvstallization bv Infrared Spectroscopy
Another method by which %C may be calculated, introduced by Nelson and O’Connor, uses the ratio of certain band intensities which occur in the infrared spectrum of cellulose to determine the degree of crystallization of the cellulose lattice.10
Infrared spectroscopy is a method of determining molecular structure based on the interaction of infrared light with molecules. Figure 3.8 shows a typical infrared spectrum of a clarinet reed (we shall return to the matter of interpreting the peaks in this spectrum later). For the purposes of calculating %C, it is only necessary to focus on two transmission (%T) bands in the spectrum, those at
1372 cm-1 and 2900 cmwhich are due exclusively to the cellulose molecule of the reed, whereas most of the other bands are influenced by the other chemical constituents. The band at 1372 cm 1 corresponds to C-H bending in cellulose, while the band at 2900 cm-i corresponds to a relatively stable (i.e., unaffected by crystallization of the polymer lattice) C-H or G-H 2 stretching mode.
The method of determining the percent crystallinity of cellulose as proposed by O’Connor and Nelson is given below.11 As an example, the “troughs” in the infrared transmission spectrum in figure 3.8 at 1372 cm-i and 2900 cm 1 are oim pads peJBJ^ui peey )auuB|0 - 8 G © Jn S y
Transmission Intensity (100% = 1) o o o P - o N5 U1 -A Ol Kj U1 4 0 0 0
3 8 7 0
3 7 4 0
3 6 1 0
3 4 8 0
3 3 5 0
3 2 2 0
3 0 9 0
2 9 6 0
2 8 3 0
2 7 0 0
2 5 7 0
2 4 4 0
• 2 3 1 0
2 1 8 0
2 0 5 0
1 9 2 0
1 7 9 0
1 6 6 0
1 5 3 0
1 4 0 0
1 2 7 0 to
1 1 4 0
1010
8 8 0
7 5 0 150
isolated. These troughs or wells measure the percent of infrared light at that
particular frequency (in cm-i) which passes through (i.e., is transmitted by) the substance without interacting with the molecular structure of the material. When
light of a particular frequency hits a molecule, it can cause portions of the molecule to vibrate, much as hitting a row of connected springs at one particular point may cause "localized" vibrations of the spring system. The amount of infrared light transmitted is that amount of light which does not interact with the molecule at that particular frequency.
O’Connor and Nelson prefer to work with absorption peaks (%A), which is simply the amount of infrared light which is absorbed, rather than transmitted, by the sample at a given frequency (%A = 100% - %T). Because of this relationship, if a particular frequency shows a trough in the transmission spectrum, it occurs as a peak in the absorption spectrum (and vise versa). Both types of measurements are used in infrared spectroscopy. For the sake of clarity, we shall base the discussion on transmission spectra, trusting that the : relationship to O’Connor and Nelson is obvious.
Since no baseline exists to measure the well depths at 1372 cm i or
2900 cm- 1, one is drawn for each of the peaks (figure 3.8), using a line drawn from the peaks at 1315 cm-i to 1372 cm i as a level line from which to measure the 1372 cm 1 well depth. Similarly, a straight line is drawn across the top of the well at 2900 cm-i.
Next, the depth of each well is determined on some convenient scale at the two frequencies (we simply measure them with a ruler in mm). Finally, the ratio 151 of the depths of the two wells is calculated and the percent crystallization is determined by the simple formula:
%C = Di372cm-1/D2900cm-'l X100% (3.4) where, is the well depth measured from the baseline at 1372 cm-i, etc.
The resulting value is a rough qualitative measure of the degree of crystallization, since the method works on a scale much courser than x-ray radiation, and hence only bulk average molecular properties are used. Since infrared spectroscopy averages over molecular states, the values for %C derived are not always accurate, depending upon the configuration of the particular molecule being studied.
A typical calculation of the %C from infrared data by the O’Connor-Nelson method is:
Di 372/D2900 x100% = 17.5mm/23.5mm x 100% = 74.5%
(3.5) which is in agreement with the values obtained via XRD.
The results of calculating %C from a small group of infrared spectra of processed ciarinet reed samples is shown in figure 3.9. The differences in degree of crystallization are quite noticeable. The %C of reeds number 1 and 5, are quite high (on the order of 60%-70%). By contrast, the %C for reeds number 2, 3, and 4 are much lower (on the order of 40%). Such a wide variation (20% or more ) in the %C makes this method somewhat tenuous for 152
T- 0 . 6 - E o o o O) CM Q
E o MCM eo û 0 .2 -
Reed Number
Figure 3.9-%C from Infrared Data for Selected Reeds 153 quantitative analysis. The infrared method is more sensitive to the loss of cellulose-like material, such as hemicelluloses, and the effects of cell wall molecular orientation, than XRD. More carefully controlled experiments than performed here need to be done to see if this method can accurately distinguishes between pristine and spent reed states of crystallization.
Extending the Infrared Testing Method
While obtaining the infrared spectra for the determination of the %C, the author noticed an interesting difference between pristine reed spectra and spent reed spectra: the presence of several additional bands in the spectra. A comparison of three spectra, two pristine, and one spent, (middle line at the start of the spectra) is presented in figure 3.10. The spectra are virtually identical except in the 1550 cm-i to 1700 cm-i and the 800 cm-i regions where the spent reed spectrum diverges from the pristine reed spectra. The additional peaks between 1550 and 1700 cm-i have been identified for the author by Andrew
Summers at the University of Miami (Ohio), using an infrared microscope as being of human origins-scrapings from the inside of the human cheek reproduce the bands seen in the spent reed exactly. This strongly suggests that the peaks at 1550, 1620, and 1680 cm -i are related to the N-H deformation
(amide II) and C=0 stretch of peptides (such as proline- rich proteins) in the lip which coat the reed over time.
It may be possible to use these bands as a way of measuring the degree of deterioration of a clarinet reed (we shall comment more on the effects of saliva 154
g
Figure 3.10-Pristine and Spent Reed Infrared Spectra 155 on the reed surface in chapter four).
Other tests for Decrvstallization
A third method which may reveal decrystallization of the cellulose matrix is known as differential scanning calorimetry (DSC). The idea behind DSC is that a sample containing many different compounds is heated, and the heat flow rate into and out of the sample (in milliwatt equivalent energy) is measured. From this data and the weight of the sample, it is possible to calculate basic thermodynamic properties of the material.
When a DSC spectrum of a spent and a pristine reed are compared, it is found that the vaporization temperature of the spent reed cellulose is lower by about fifty degrees than that of the pristine reed (onset temperature 475° C for pristine vs. 416° C for the spent reed), as in figures 3.11. These values are determined by extending a line from the slope and the straight line portion before and after a weight loss. The intersection gives the onset temperature of vaporization.
This lower onset vaporization temperature of the spent reed is consistent with a decreased %C in the spent reed compared to the pristine reed.
Thermodynamically, more energy (which is measured by the enthalpy of vaporization) must be put into the crystallized form of a material to vaporize it, in order to randomize or destroy the extra stability gained by the lattice ordering
(i.e., to overcome the lattice stabilization energy), than for a more amorphous form of the same material. 156
Curve îi ose File info, 00082 Fri Nov 22 16,35,IB 1991 Soap le Weight, 1.480 »S Clorlnet Reed Prietine TS # I Clcrinet Reed Prietine TS Hect Flo* (sV> S 10.00 9 2 Clorlnet Reed Ueed K Heat Flo* (mM) S 5.00 ■
-5.00 - S -10.00 -
-15.00 -
•2 0 .0 0
•25.00 -
•30.00
•35,00 -4— 50.0 250.0150.0350.0 450.0 550.0 10 C/aln in Stognent Air Temperature (*C) F.K. CelJaqher *0.0 c/»,n PERX2N-ELMER 7 Serlee Thermal Analysle System Hon Nov 25 13,16,02 1991
Figure 3.11-Differential Scanning Calorimetry Plot of Pristine and Spent Reeds 157
Thus, it Is possible that the Increased melting point of the pristine reed Is due
either to the extra stability of the crystallized cellulose, or possibly due to the
presence of hemicelluloses (which are missing In the spent reeds, as
mentioned above) In the cell wall matrix, which would affect the molar
composition of the cellulose and lead to boiling point elevation (as In the
familiar case of salted water). It Is not possible at this time to determine which of
these phenomena lead to the change In vaporization temperature.
Degree of polvmerlzatlon
If the degree of crystallization measures the amount of ordered cellulose
which exists In the total amount of cellulose material, then another number, the
degree of polymerization, measures the number of cellulose molecules
strung together In each extended cellulose lattice. This number Is determined
by dividing the molecular weight of the cellulose lattice by the weight of one
cellulose molecule (not celloblose, but a single molecule):
Dp = wt. polymer / wt. monomer
(3.7)
Typical values for the Dp range from 15,300 molecules of cellulose for
California cotton still In Its capsule, to 305 cellulose molecules for rayon fibers.
The other carbohydrate compounds which form the cell wall matrix, the
hemicelluloses mentioned above, by contrast have Dp values of about 150 for mature tlssue.i2 158
It has not been possible in this study to measure the Dp of clarinet reeds,
since this involves extensive laboratory preparation of the sample, (e.g.,
techniques such as vapor phase osmometry, viscometry, light scattering,
sedimentation, etc., which are typically used to measure Dp) and is something
which must be reserved for future studies. The Dp for the cellulose in the cell
wall matrix in Arundo donax, for this study, will be assumed to be approximated
by the value for cellulose, which is on the order of 700 cellulose molecular units.
Fibrils
Cellulose molecular lattices link together to form long chains, which can form even more complicated three-dimensional lattice structures due to hydrogen bonding. These extended lattice structures are calledmicelles, and there is a huge literature on micelles in biophysics, as this is a topic currently of much interest in polymer chemistry and physics, if these chains and resulting lattices are sufficiently ordered and extended, a larger visual macromolecular structure is often formed. This mesoscopic structure of cellulose reveals itself as long slender thread-like fibers, calledfibrils (figure 2 .4 3 ).13
Fibrils of this size, just above the scale of the extended polymer lattice micelles of cellulose (= .003 |i-.008 |x), are technically called elementary fibrils or microfibrils, and just as thread or twine contains smaller threads twisted together to form the larger threads, elementary fibrils join together to form larger thread-likefibrils (sometimes called macrofibrils). It is these fibriis which link together to form the matrix of the cell wall. 159
The fibril structure is more complex than implied above, however, because hemicelluloses (the other class of carbohydrate compounds in the cell walls of plants) tend to form sheets or chains parallel to the outer surfaces of the cellulose micelles of the fibrils, and hydrogen bond to the cellulose. On the opposite side of the hemicellulose sheet, glycoproteins cross-link the cellulose-hemicellulose elementary fibril to other fibrils, to form a quasi-lattice of elementary fibrils, creating a macrofibril. In addition, lignin bonds to the hemicellulose material in the macrofibril, stabilizing the cell wall matrix, by
“filling in the gaps in the matrix”, but also slightly lowers the elastic strength of the material.
There are several theories which have been presented to explain the formation of the cell wall from fibrils: the multinet theory, the hélicoïdal theory and an extension of these theories based onperiodic microstructuring of a composite material, by Niklas. We shall refer the reader to the endnotes for more detail, since such a discussion is outside of the scope of this document, even though an understanding of the influence of the properties of the cell wall fibrils of Arundo donax may have importance implications in the growing of the plant for clarinet re e d s . 14
Hemicellulose
The other class of carbohydrate compounds found in clarinet reeds are the hemicelluloses, so-called because at one time they were thought to be steps in the natural biosynthesis of cellulose. The particular generic hemicellulose 160 found in clarinet reeds is the same one found in many softwoods, namely, arabino-4-O-methyl glucuronoxyian (figure 3.12).The molecular structure of this compound is more complicated than simple cellulose, and is formed by the linking together of so-calledxylan units, more specifically,
(1->4)-linked-p-D"Xylopyranose (abbreviated, Xyl), to form a backbone.
The structure of this xylan is shown in figure 3.12.
From the parent backbone, two different chemical units attach or branch from different and sometimes variable points on the backbone:
L-araboRofuranose (abbreviated, Araf), and 4-0-methyl-a-D-glucuronic acid (abbreviated, 4-Me-GlcA), as shown in figure 3.12. Araf typically attaches at the so-called 0-3 position of the Xyl backbone, which means that an oxygen bridge connects the Araf molecule from carbon number 1 of its ring system to the carbon numbered 3 in the Xyl ring system (so, more exactly, one could call this a 1-0-3 bridge, but convention is to simply assume that the external attaching molecule does so from the number 1 carbon atom in the ring unless otherwise stated). 4-Me-GlcA has variable bridging positions within the
Xyl backbone, but is typically at the 0-2 position.
The generic structure of the primary hemicellulose in Arundo donax mentioned above (which we shall abbreviateAMGX, hereafter,) and shown in figure 3.23, consists of branching Araf and 4-Me-GlcA units, but the exact locations are not specifically known, so the structure indicated is to be taken as an approximation, consistent with known chemical knowledge obtained through 4-O-methyl-ct-D-glucuronic acid :00H L-arabi nofuranose OH /
OH OH OH
OH OH OH
( 1-->4)-1 i nked-p-D-xy lopy ra nose ( b a c k b0 n e )
Schematic Structure
j 0 -2 0 -3
(0 -2 etc., => oxygen linkage)
# =Xy1
= 4 - Me-01 uA
= Araf
Figure 3A2-Arundo donax Hemicellulose 162 degradation experiments.
Different softwoods (and grasses, such as Arundo donax) have different concentrations of the Araf and 4-Me-GlcA side-chains. For exampie, Fengel and Wegener summarize a number of sources which show that the ratio of Xyl to 4-Me-GlcA varies in different softwoods from 5 : 1 to 6 :1 in softwoods, although extremes of 4 : 1 and 3 : 1 are known; the ratio of Xyi to Araf varies from 6 : 1 to 10 : 1 in softwoods.i6 Taken together, they give an averaged ratio of Xyi to 4-Me-GlcA to Araf of 8:1.6:1. In addition, softwoods also contain higher concentrations of 4-Me-GicA than hardwoods. Using Sodium Hydroxide at varying concentrations as an extractant, Solomon et. al, were able to obtain hemicelluiose giobules and determine that the ratio of Xyl to Araf is 5.8 : 1, and
Xyl to 4-Me-GlcA is 10 : 1 in Arundo d o n a x .i7
As Arundo donax matures, the concentration of hemiceiluioses and hemicellulose components changes. Since it was known from previous work that the relative amount of mature tissue greatly increases from the apex of the
Arundo donax stem down to the bottom of the stem, in a relatively immature
(one month old), but fast growing stem, Joseleau and Barnoud excised tissue from only 1 to 3 cm from the top of the stem, representing the youngest portion of the plant, from 9 and 15 cm from the top, representing the middie stage in development, and from 21 centimeters from the top (i.e., the bottom of the stem), representing the oldest portion of the plant. They found that the total hemicellulose content changed from 34% to 44% to 25% in the early, middle, and late tissue, respectively. 18 163
More specifically, the Xyl concentration changed from 68% to 89% to 81 %, while the Araf concentration decreased as the plant matured. They interpreted these results to the increased used of hemicellulositic material in the formation of the primary thickening of the stem, which typically occurs after the initial primary (vertical) growth period of the plant, and before stabilization of the stem size.19
The degree of polymerization of AMGX also changes as the plant matured: from 63% to 91% to the stable 151% mentioned earlier in this chapter during the rather general discussion of Dp. This corresponds to the observation that as the size of the vascular tissue increases, more of the hemicellulose is polymerized into the cell walls.
A comparison of the concentration of Xyl in different sections of a maturing
Arundo donax indicates that there is variation not only over time, but also within the different cell types. It has already been mentioned that the Xyl concentration changes from 34% to 44% from young to middle-aged tissue. More specifically, this is true for vascular tissue. Parenchyma tissue shows an even larger change: from 24.3% to 51.2%. In both types of tissue, the Araf concentration fell off dramatically: 15.9% to 2.6% for vascular tissue, and 7.3% to 2.6% for parenchyma.20 These results are also consistent with the primary thickening meristematic growth of the stem mentioned above.
The Role of Water and Hemicellulose
The purpose of hemicelluloses in Arundo donax, and woods in general, is to aid in the absorption of water. Hemicelluloses tend to be hydrophillic in nature. 164
and allow for the absorption of water molecules in the interstitial spaces of the
cellulose crystallite lattice. A related class of molecules, pectins, serve this
function even more in most woods (not, however in the grasses, since the
concentration of pectin is low).
Xylans may be isolated and grown into extended crystal structures. These
crystals may be hydrated, and show the relative hydrophyllicity of AMGX or
similar xylans. Upon reaching 100% humidity the crystal size of a
representative xylan crystal changes 5% in width and 1% in height.2i Partially
because of the steric hindrance of the side-chains in Xyl and other xylans, the type of hydrogen bonding which is seen in the cellulose unit crystal is not possible, and it is the addition of water molecules, with their propensity for hydrogen bonding, which is thought to be responsible for enabling the xylan crystal structure to form.22 The “piggyback” nature of the borrowing of the hydrogen bonds of water which stabilizes the xylan unit crystal (although, probably not as much as the “purer” hydrogen bonding in cellulose), and as well as the presence of the protruding side-chains of the molecule, explains the lower Dp of the hemicelluloses compared to cellulose.
Hemicellulose Degradation
It is sometimes possible to obtain qualitative data on the composition of large molecular entities in a material by the use of a technique known as thermogravimetric analysis (TGA), and we use it here to study the effect of saliva on hemicellulose in the reed material. The idea behind TGA is that, as a 165
sample containing many different compounds is heated, each compound will
boil off at its particular vaporization temperature, resulting in a drop in weight as
the particular compound is released in the from of a gas. When samples of
pristine and spent reeds are placed in TGA chambers and slowly heated and the weight loss recorded, the various volatile compounds contained in the reed
can sometimes be identified.
Two typical TGA spectra, spectra pi, and spectra p2, from two different
excised samples of a single pristine reed (about five mg per sample) are shown
in figure 3.13. The author is extremely grateful to Dr. Patrick Gallagher of The
Ohio State University department of chemistry/material science, who performed the TGA (and DSC) analysis, for donating his time, expertise, and his own equipment in this research.
The plots show a striking resemblance to the TGA curves for cellulose, as should be of no surprise, since most of the reed material is cellulositic.23
Differential plots (which show the change in slope of the original spectra and makes the weight loss easier to see) are overlayed in each case shown in figure 3.13. A tentative analysis of the loss in weight for the different molecular entities in the differential plot for the two pristine material is as follows (some form of evolved gas analysis would be needed to definitively identify the compounds); 166
^>va 11 TGA Fila Info, T383B Mon Nov 25 C5,25,47 1991 Soaplt Walght, 4.342 "g Clcrinat Raad Prlatlna TS f : Clorlnat Raad Prlattna TS WolghC (Wt. %) 100.0 -F # 2 let Darlvotlva (Z/eln x 10 ) 10.0
90.0 0.0
80.0
70.0 •30.0 b ±? 60.0 4 "40.0 & 50.0 4 e •50.0 40.0
30.0 ■; ■70.0
0.0 200.0 3CÔ.0 500.000Ô.0 700.0 800.0 900.0400.0 10 C/eln Sn Ar Tmparotura (*C1 P. K. Gollodwr îSSi: Ut: i Îiæ: feg — 5'§ÏÏS^oi/^=iy.i.syrt« M— M.W. oc ne.cT. 90 raoi '
Figure 3.13-TGA Spectrum of Two Pristine Clarinet Reeds 167 Figure 3.13 (cont.)
Curve ]i TGA File Infoi T383S Fri Nov 22 18,54,09 1091 Sample Weight, 4.528 mg Prlmtlne ftemd TS 0 I Prletinet Roed TS Weights (Wt. V § 2 let Derlvotlvm (Z/sln>
80.0 0.00
-5.00 2 70.0 Q •10.00 é •15.00 > & 50.0 •20.00 e 40.0-}
30.0 •25.00
20.0 -30.00
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0 .0 0.0 200.0 300.0 500.0 10 C/min in Air Teperoture C*D PERKIN e&S ? fnat tS tiS 7 Seriem^ThermalSeri______System Fri Nov 22 16,56,31 168
100° C-water, (approximately 5% loss by weight ( = Ibw)), 2200 C-AMGX (15% Ibw), 2800 c-LlgnIn, and some types of non-AMGX hemicelluloses, possibly MGX (approximately 18% Ibw) 3100 c-Llgnln (present In pristine reed sample p i. Not present In used reeds, si, Sa) 3500 C-cellulose (approximately 55% Ibw).23
Table 3.3-TGA PeakAssignments24
The presence of the additional peaks in spectra pi (noted above) may be due to a different sampling environment (i.e., having been chosen possibly from a region richer or poorer in vascular tissue than the material in spectrum 2 p), or due to different machine settings, as the tests were conducted on two different dates.
When a clarinet reed is initially selected and played, most musicians notice a sweet taste to the reed. We believe this taste is due primarily to the presence of
AMGX in the reed (having side-chain structures related to many other sugar-like glucosides). The reed is also extremely hydrophillic (we shall discuss the water capacity of clarinet reeds in chapter four).
As the reed is played upon, the sweet taste gradually diminishes, and the reed becomes gradually less hydrophillic, until some stable point is reached.
This is the point at which the reed is generally said to be “broken in.” These effects are probably due to the loss of hemicellulose in the reed cell wall matrix, and thus, it is this chemical degradation which is mainly responsible for the breaking in of a reed.
Considering that the reed is being subjected during the course of playing to something, which, as a chemistry laboratory procedure which could be 169
described as, “immerse in a water-filled, alkali/enzyme bath and shake
vigorously,” it is not difficult to understand why this type of material, which is
soluble In mild bases, is leached out of the reed cell walls.
Saliva is stimulated by the infusion of Ca2+ ions reaching the Acinar cells of
the salivary gland, and possibly the slightly alkali nature of these ions, along
with the action of such glucose degrading enzymes as amylase in solution,
along with the physical excitation of the reed, is enough to remove the AMGX in
the pristine reed. This is not to say that saliva is alkali, in and of itself (it is not,
except when the flow rate is sufficiently high, as explained in chapter four), but
rather that AMGX is sensitive to the presence of several compounds and ionic
species contained within saliva, some of which, such as Ca2+ andHCO 3- have
alkali properties and which can react with the AMGX when near it.
The loss of AMGX is shown in the TGA spectra, Si and sa in figure 3.14 (each
sample excised from the same single spent clarinet reed, but, as earlier, run
under different machine settings). These TGA spectra may be compared with the pristine samples pi and pa shown earlier (figure 3.13). A comparison of the
differential plots is shown in figure 3.15. The loss of the peak at 220 oC in the
spent samples indicates the absence of AMGX in the spent reeds. Lignin,
however, is unaffected, as both reeds show a peak at 280 oC.
As mentioned, MGX (4-0-methyl glucuronoxyian) is also present in the reed,
as identified in the spectra above at 310° C, and this peak also appears to be
removed by saliva, as it is missing in the spent reed as well. 170
Curv« It TGA Fll« Infoi T3B38 Fri Nov-22 38,55,37 3883 SapU Volghti 5.273 mg Clorlnmt Rood U##d K Clorlmmt Rmmd Uwd K
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Figure 3.14-TGA Spectrum of Two Spent Clarinet Reeds Figure 3.14 (cont.) 171
Curve 11 TGA File Info, T3639 Mon Nov 25 :1,50,58 199: Sample Weight, 4.941 eg Clarinet Reed Ueed K # 1 Clorlnet Reed Ueed K Weight: (Wt. Z) 0 2 let Oerlvotlve (Z/mln x 10 ) 10.0 90.0 0.0
00.0 •10.0 70.0 Q ÿ 60.0 •30.0 ft 50.0- •40.0 40.0 - •50.0 30.0
20.0 •70.0 10.0
0.0 100.0 200.0 300.0 500.0 C 700.0600. 000.0 900.0 10 C/mln in Ar Temperature <*C) P^^CoIlagher iin lUTi,* ia.fl e/i 7 Serlee Thereol Analvele Syetem Mon Nov 25 12,29,00 1991 ' 172 Curve 11 TS.* Fila info, T3B36 Fri Nov 22 Î8i55,37 199: Soaplo Weight,5.273 eg Clarinet Reed Ueed K U I Clcrinet Reed Ueed V. let Zerlvetive C/e in) § 2 Prietine Reed TS let Oerlvotlve C/eln) C. 00
e -10.00 I
100.0 300.0 400.0 500.0 600.0 700.0 900.0 10 c/eln In Air Teeperoture (*D P.K. Colleger PERXIN-ELMER asi: I «%: 8:8 7 Serlee Thereel Analvele Syetea Kon Nov 25 12,49,12 %%] ^
Figure 3.15-Comparison of Differential Plots of Pristine and Spent TGA Spectra 17 3 Figure 3.15 (cont.)
Curv# Il ToA fllQ infoi T3S38 Ken Nov 25 C9i25i47 1S81 Seapl« Vsightt 4,342 mg Clsrinat Read Pristina TS tf ! Clorinst Raad Pristina 75 1st Oerlvctivs (I/sin x 1C 10. C -i § 2 Clorinst Rasd Ussd K 1st Oorlvotlva CZ/aln % 10*^) 0.0
„ - 10.0 1 - -20.0 4 ; ! - -30.0 -i I ? •"“■“1 5 -50.0*1 I -60.0 J
-90.0
;cô.o 200.0 300.0 400.0 600.0 700.0 600.0 600.0 10 c/min in Ar Ttmpsroturs <*C> P. K. Golloohsr I SATCI* 1 0 .0 C/mir PERKIN-£U€R g 7 Sariss Thonsol Anolysis Systom Mon Nov 25 12, 42i 45 I%1 174
Infrared Identification of Hemicellulose
Earlier in this chapter we discussed the possible role of infrared
spectroscopy in determining the degree of crystallization of the reed material.
Infrared spectroscopy may also be used to identify compounds by their
characteristic absorption peaks.
Marchessault and Liang have done extensive analysis of the infrared spectra
of xylan structures.25 On the basis of their research into the MGX, it is possible
to identify some of the peaks in the infrared spectra ofArundo donax as being
of AMGX origin. A complete identification of the peaks in the spectra are given
in the section on lignin later in this chapter.
Interestingly, the infrared spectra of spent reeds indicate that AMGX is
present in the same amounts in both spent and pristine reeds (figure 3.10), if
one assumes that the band between 1000 and 1150 cm i is due to the presence
of AMGX, as the work by Marchessault and Liang seems to suggest. This
discrepancy with TGA is something which must be explored further, as the
decrystallization results and TGA results seem to indicate some change in the
composition of the reed hemicellulose due to saliva immersion. It is possible that the reaction with saliva is more complicated than the simple leaching model would indicate. In addition, there are biomorphological differences in infrared
spectra depending upon concentration of ground tissue and vascular tissue, which have different chemical environments. Most of the work done in this chapter was using infrared microscopy, which would be more sensitive to these tissue/environment differences. 175
To summarize, later harvesting of Arundo donax leads to stable concentrations of AMGX In the plant stem (about 25%). Alternately, younger stems, sectioned only near the base of the plant, show the same trend.
Ultimately, AMGX appears to be leached out of the material relatively early on In the playing life of the reed (a detailed time-dependent study via TGA or Infrared spectroscopy of the rate of loss of AMGX due to saliva Immersion time Is still wanting).
Llanin Preliminaries
The last major chemical component (20% to 40%) of Arundo donax Is lignin
(from the Latin word for wood). This highly complex gummy filler substance is formed from dead plant cells, and usually occurs as a result of the aging process of plants. Lignin protects older plants from pathogens and water, stabilizes the cell wall matrix, and gives viscous shock protection and some plasticity to the plant.
There are three major types of lignin which exist In different hardwood, softwoods (and grasses): guaiacyl lignin, syringyl lignin, and, guiacyl-syringyl lignin (for reason which will be explained, momentarily).26
Each type of lignin Is formed from the Incredibly complex polymerization of one or more of three simple molecular units of propyl alcohol (PrA) which have a different phenol ring derivative attached at the third carbon: p-coumaryl alcohol (PA), coniferyl alcohol (CA), and sinapyl alcohol (SA) (figure
3.16). It should not be Inferred that there Is a one-to-one correlation between 176
OH- /y ^ CH2CHCÜOH
NHg tyrosine
i4 \ CH^OH CH OH CHgOH I CH CH CH II II II CH CH CH
s\ OCH 3 OCH OCH I OH OH
p-coumaryl coniferyl si napyl alcohol alcohol alcohol PA CA SA
e e OCH OCH C9 OH OH •O p-hydroxyphenol yuiacayl S i napyl 1 unit (H ) unit (G) unit (S ) ë N c « a HC=0 HC=0 HC=0 2 £
OCH OCH OCH OH OH OH p-hydroxybenzaldehyde vanillin syri ngaldehyde H (y) V S (y)
Figure 3.16-Llgnln Preliminaries 177 the three alcohols and the three above-mentioned lignins. That there are three
of each is purely coincidental, as the three lignins mentioned above each
contain mixtures of ail three alcohols, and derive their names from the
by-products of chemical analysis of the lignins (to be explained shortly).
The polymerization of the building-biocks mentioned above results in a
molecular structure composed of many linked benzene/phenoi ring systems, which has not yet been completely worked out for any of the lignin types, and estimates or models of the the number of rings involved for a single molecule of a prototypical lignin range from sixteen rings to ninety-four rings! Such aromatic entities, having large numbers of carbon atoms, typically appear as gummy substances, and lignin is no exception, as mentioned above.
It is not possible to go into the incredible amount of biosynthesis which creates each of the three types of lignin, nor their polymerized forms, and for such a discussion the reader is referred to either Fengel and Wegener, or
B ra u n .2 7 In a simple-minded manner, however, it is possible to imagine that lignin is formed in most true woods (i.e., those plants having secondary growth) from glucose, which is converted to a compound called shikimic acid (this method of biosynthesis of lignin is called, not surprisingly, the shikimic acid pathway), which eventually works its way through different biological reactions to one of the three alcohols mentioned above, which then begin to polymerize.
Grasswoods, on the other hand, arrive at these alcohol precursors by a different route than the shikimic acid pathway, starting instead with tyrosine,
(which is known also as the phenylpropanoid, p-hydroxyphenylalanine). 178
Of the three types of generic lignlns, the gualacyi llgnin, which comprises most softwoods, is derived primarily from coniferyl alcohol. Hardwoods contain mostly guiacyl-syringyl lignin, which is a copolymer comprised of the coniferyl and sinapyl alcohols in ratios of 4 : 1 to 2 : 1 . 28 Sinapyl lignin is found mainly in compression wood, which is the type of wood which results when a plant is subject to bending or is injured, it contains large amounts of p-hydroxyphenol elements, and is sometimes alternately called p-hydroxyphenyl lignin.
These are several ways to classify the three types of lignins mentioned above, as might be expected from their complex molecular composition. If one ignores the propanol unit which is common to all of the three precursors mentioned above, and is only concerned with the remaining aromatic substituent, then one may call these guaiacyl units (from coniferyl alcohol without the propanol subunit, i.e., CA without PrA), syringyi units (from sinapyl alcohol without the propanol subunit, i.e., SA without PrA), and p-hydroxyphenyl ( from the p-coumaryl alcohol without the propanol subunit, i.e., PA without PrA ). These aromatic subunits are abbreviated,G, 8, and H, respectively (i.e., G =CA without PrA, S=SA without PrA, H=PA without PrA).
When a lignin is reacted with nitrobenzene in a process called nitrobenzene oxidation, the biopolymer is fractured into the three basic constituent molecules mentioned above (G, 8, H), only converted to their aldehyde form.29 The guaiacyl ring (G) in its aldehyde form is simply vanillin
(i.e., G->V). The aldehyde form of the syringyi unit is syringyialdehyde (i.e.. 179
S-->Sy). Finally, the aldehyde form of the p-hydroxypenyl subunit is p-hydrcxybenzaldehyde (i.e., H—>Hy)). Since there is a one-to-one ratio between the number of moles of the aldehydes formed through the nitrobenzene oxidation process (which is often easy to measure), and their original aromatic subunits counterparts (G ,S,and H), measuring the number of moles of aldehyde formed suffices to determine amount of the corresponding aromatic forms. The reader should not be surprised that the two labeling systems are essentially the same, since they refer to related compounds, with V being preferred for the aldehyde form of G, and Sy, and Hy being use in this document (the literature uses S, and H for the aldehyde forms of S and H, as well but this might confuse the reader) for the aldehyde derivative.
Depending upon which lignin is used, different ratios of these three subunits,V, Sy,Hy (or G, S, H) are obtained by nitrobenzene oxidation. As mentioned earlier, most softwoods contain large amounts of CA, and hence it comes a no surprise that nitrobenzene oxidation yields large amounts of vanillin, indicative of the guaiacyl subunit, which is derived from coniferyi alcohol (CA). Hardwoods, as mentioned above contain both CA and SA and yield primarily V (G) and Sy upon nitrobenzene oxidation. Grasswoods contain primarily CA, but also sizable amounts of both SA and PA, so it should come as no surprise that V,Sy, and Hy products are formed by nitrobenzene oxidation.
Based upon these results, one may refer to softwood lignins asG-iignins, hardwood (dicot) lignins as GS(y)-iignins, and grasswood lignins as
GS(y)H(y)-lignlns (the usual literature omits the y). 180
Arundo donax Lianin
With these preliminaries in mind, results of studies of Arundo donax lignin may be summarized.
All three lignins covalently bond to most of the various types of hemiceiluloses found in plants. Since the ratio of Araf to Xyl is higher in the lignin obtained via the residue when the mill wood process is applied to a stem of Arundo donax than that reported for the hemicellulose of Arundo donax,
AMGX, Diesheng Tai, et al., concluded that that the bonding between the GSH lignin of Arundo donax and the major hemicellulose, AMGX, occurs typically at the site of the side-chain unit, Araf, which was mentioned above (figure 3.12) in the discussion of hemicelluose.30
This group also found that the ratio of V, Sy, and Hy (i.e., G, S, H) were,
1 ; 1.14: .34 (10.87%, 14.98%, 2.95%, by weight of the milled wood process residue) respectively, confirming that this lignin is a composite GSH-lignin. The molecular weight, indicative of the biopolymer, is between 1000 and 10000
Daltons, which is similar to most grass lignins, and indicate that up to 100 carbon rings may be found in the complex biopolymer, as has already been mentioned.
Joseleau et al. found, as to be expected, that there is also a correlation between age and lignin concentration.3i The concentration of lignin increases about ten-fold as one goes from the top (younger portion) of the stem to the bottom (older portion). This group also found that although the concentration of
G is always large, as the plant matures, the amount of Sy increases. 181 presumably reaching the roughly 1 : 1 ratio mentioned above by Diesheng et al.
We shall discuss the implications of these findings on the biomechanics of the clarinet reed later, since the presence of the rather amorphous lignin in the relatively flexible cell wall structure of Arundo donax may be responsible for changing the plant stem from one in which there is only one naturally dominant plane of material strength (a situation common in true woods) into one in which each of the x, y, and z planes are of equal strength.
Spectroscopic Methods of Lianin Determination
There is no iaboratory chemical process which will precisely determine the concentration of lignin in a given sample of wood, although nitrobenzene digestive methods are commonly used. In the area of machine testing, there are several ways in which lignin may be studied non-destructively, which yield additional information. The three most common are infrared spectroscopy, ultraviolet spectroscopy, and nuclear magnetic resonance spectroscopy.
The easier technique to use is ultraviolet spectroscopy, in which the absorption or reflectance of ultraviolet light of various wavelengths
(frequencies) is measured. Lignin, containing many aromatic rings, shows an absorption maximum at wavelengths of 280 nm (nanometers), and a shoulder in the 230 nm wavelength ran g e.32 Another very large peak occurs in the 200 to 208 nm range. Deisheng et al. found that the ultraviolet spectrum of Arundo donax showed the peaks at 280 nm and an additional peak at 310 nm (it is not reported if they found the peak at 200 nm, although they almost certainly did).3i
The position of the 280 nm peak changes as the lignin type changes, thus 182 allowing for confirmation of lignin types which may be present in a sample.
Softwood lignins have the second peak at 280 or higher nm, while hardwood lignin shows the peak at lower wavelengths (270 nm-275 nm), which is indicative of the larger amounts of the Sy units in hardwood, which have higher symmetry than the the G units found in softwoods (recall that hardwoods are
G-Sy lignins, and softwoods are G-lignins). Interestingly, since the amount of
Sy increases as Arundo donax ages, it should be possible to qualitatively determine the relative maturity of samples in the growing field by the shift in the
280 nm peak location as the stems mature. Also, the peak at 310 nm may also show variation with age, since it is primarily due to the presence of Hy units in the stem.
Infrared spectroscopy, mentioned earlier, is also useful in revealing the presence of lignin in a woody sample, although the interpretation of which type of lignin is present is not straightforward.33 a typical infrared spectrum is shown in figure 3.17. As mentioned earlier, the troughs in the spectrum corresponds to the decreased transmission of infrared radiation at that frequency (or equivalently, wavelength, since the two are related by a simple formula). When
IR radiation is absorbed, it sets into motion the internal modes of oscillation of a molecule. Different wavelengths effect different modes of vibration (such as bending of certain elements on the molecule, or stretching of some of the atoms, etc.).
A list of the internal modes of oscillation of the three principal components of
Arundo donax (C = cellulose, H = hemicellulose, L = lignin) corresponding to uieiSXBUop opunjy ;o lunjpads paJBJjU|-/|. s ajnSy Transmission Intensity (100% = 1) o 0 o o o o o to CO Ul 01 OJ CO U l 4000 3876
3752
3628
3504
3380
3256
3132
3008
2884
2760
2636
2512 o 3 2388 2264
2140 s 2016
1892
1768 O 1644
1520
1396 1272 W 1148 W 1024
900 to 776
£81. 184 the peaks in the IR spectrum in figure 3.17 is given in table 3.2. This table was compiled by examining the reported transmission peaks of the three components, separately.34 For the most part, the peaks are distinct to each species, allowing precise identification of bands to be given. For instance, the bands at 833, 1510, and 1600 cm-i are diagnostic for lignin, while the broad band at 1000-1120 cm-i is diagnostic for AMGX (although cellulose peaks do occur here also, but are masked). The peak at 1600 cm-i may sometimes be used to indicate the presence of bound intercellular water, if the concentration of lignin is sufficiently low to allow the peak to be expressed. The fact that the peaks at 1600 and 1510 cm-i are so strong indicates that this is truely a
Guaiacyl (G-)lignin from grasses and softwoods, as opposed to a
Syringyl-dominated GS(y)-lignin as found in hardwoods.
The shoulder at 1550 is problematic. In spent reeds, this may indicate the presence of amide N-H deformation, however, it is so masked by the lignin antipeak that this is difficult to see. This amide peak may possibly be the identity of the peak at 1530 cm-i in figure 3.29 in the bottom spectrum. The
1600-1700 cm-1 region shows the presence of either 0 = 0 stretching in lignin (a single peak) in pristine reeds, N-H deformation (triplet of peaks) of the primary amides in the proteins in saliva in spent or played reeds, or adsorbed water in the reed cellulose matrix. We have indicated these possibilities by labeling the peak OLA. Several of the peaks are common to all three species (such as the
3200-3400 cm-1 peak), and we have so indicated this on the spectrum.
It may be possible to use the intensity of the peaks to determine various 185 Symbol Frequency fcm'^) Çomments(see endnote 34)
LI 833 Aromatic C-H out-of-plane deformation L2 870 Same as LI HI 897 C-1 group frequency or ring frequency H2 990-1120 C -0 stretch (cellulose peaks buried in region also) H3 1130 Antisymmetric in-phase ring stretch H4 1160 Antisymmetric bridge C-O-C stretching L3 1240 Guaiacyl ring breathing with CO-stretching (may be 0 -H in-piane bending in Hemicellulose) L4 1320 Syringyi ring breathing with C-O stretch L5 1370 C-H deformation (symmetric)
C l 1420 C-H2 symmetric bending L6 1460 C-H deformation (asymmetric) L7 1510 Aromatic skeletal vibrations (signature for lignin) AL 1550 L =Lignin “antipeak” , A = secondary amine N-H deformation (an unidentified peak may occur instead at 1530 cm'^ in some (pristine?) reeds) LB 1600 Aromatic skeletal vibrations (also, indicates prescence of
intercellular H2 O in cellulose at 1595 cm"^) OLA 1650 C=water of hydration (cellulose), or L=carbonyl stretching (para-substituted aryl ketone), A=N-H deformation, 1° amide (1620-1650 cm'^), or C = 0 stretch, 1^ amide (1620-1670 cm"^) H6 1720 C = 0 stretching (acid) CO2 1780-2700 Air (carbon dioxide), unidentified peak at 2100 cm"^
L.H,C 2780-2880 L=OH-stretch in methyl and methylene groups (2880, 2940 cm""'), H=C-H stretching (2873,2914 cm'"*),
CH2 antisymmetric stretching (2935 cm'^ ), C =CH 2
symmetric stretch (2851 cm"^), C-H stretch (2907 cm'^) H,C,L 3250-3500 H =0-H stretch, C = 0 -H stretch, L = O-H stretch
Figure 3.18-lnfrared Peak Assignments for Arundo donax Spectrum 186
properties (such as the degree of polymerization and the maturity of a given
specimen) of the three species, such as lignin, of Arundo donax, since
Kawamura and Higuchi have shown that the ratios of G to S to H may be
classified according to IR peak information, although such studies have not yet
been undertaken for Arundod o n ax.35
What is reasonably clear from the data presented in figure 3.20 shown earlier
is that Arundo donax lignin is not changed appreciably over the course of the
playing life of the reed. There appears to be little difference in peak intensities
from pristine to spent reeds in general, and no profound changes in peak
locations or intensity (except for the water peak at 1600, and 1650 cm-i, which is
expected to change intensity due to drying) or the manifestation of new peaks
(other than the amine peaks from saliva, which do affect the reed cellular matrix,
as mention in chapter four). Thus, the reed appears to be remarkably stable over its playing life. The increase in bacteria cellulose in the reed due to oral
microflora (see chapter four), also has not been measured.
In regards to the final spectroscopic technique of studying lignin (and the reed
in general), Deisheng et all. report a very complex Nuclear Magnetic
Resonance spectrum, involving some 35 differentp eaks.36 We shall not attempt to summarize their work, as it is quite complicated, and we refer the reader to the original article. Using this information, however, they were able to confirm that the G and S units predominate over the H unit concentrations, as
discovered through chemical degradation independently by Joseleau.37 187
Cell Wall Chemistry
In terms of the relative contribution of the three principal classes of clarinet
reed components which occur in the cut plant stem: cellulose, hemiceiluloses
(among which, AMGX, is the most abundant), and GS(y)H(y)-lignin, the
research is summarized by P urdu e.3s On average, the components contained
in the stems five different plant stems analyzed by five different researcher
digested to yield 42-50% cellulose, 20-24% hemiceiluloses, and about 10-20%
lignin. The amount of cellulose in Arundo donax is comparable to that in wood
(40-50%), while the lignin percentage is iower than wood (20-40%), higher than
other grasses (12-19%), and approximately the same as other types of cane,
such as Bamboo (14-32%). As Pointed out earlier, the percentage of
hemicellulose is roughly the same as for the cane grasses (such as Bamboo),
hardwoods and grain grasses (15-30%), but more than for most softwoods
(8-14%). The ash content (approximately 4%), compares favorably to other grasses, but is less than for woods (= 1%). The total silica content of the stem
(epidermis and soft tissue) was 1-2%.
Although it is not possible to examine in detail the chemical contents of the cell walls of Arundo donax within the confines of this document, some broad conclusions may be drawn from work on related wood species. Softwoods tend to show a larger concentration of lignin ( 60%) than cellulose (14%) in the compound middle lamella (middle lamella and primary wall). In the secondary walls the situation is reversed, with more cellulose (60%) than lignin (27%).
The amount of cellulose in the secondary wall (most noticeably the 82 layer) 188 gradually Increases as the plant ages and more cellulositic material is required in secondary growth.
Since Arundo donax does not a have a secondary wall structure, it is reasonable to assume that most of the lignin in the stem is deposited in the middie lamella, and that most of the cellulose and hemiceiluloses are deposited in the primary wall, with the concentration of hemicellulose gradually changing over time due to growth requirements.
Unfortunately, at this time, there is no quantitative way of measuring the total lignin concentration of a plant stem, since chemical extrative methods tend to adulterate some portion of the lignin. One method, suggested by the work of
Goring, and reported by Fengel and Wegener, is to thin-section the material and study the cross-sections by means of ultraviolet microscopy.39 Since lignin is ultraviolet active, the exact location of the p-alkylphenol entities contained within the lignin in the thin-section of stem cell walls is made to fluoresce using a monochromatic 280 nm light source (i.e., the aromatic constituents, such as G,
8, and H).
This type of study may be crucial in the classification of the quality of Arundo donax cane and the resultant clarinet reeds; however, since the location of lignin throughout a clarinet reed must be determined without tampering with the reed (something not possible with the ultra thin sectioning required for UV microscopy), another possible method for revealing the lignin structure in clarinet reeds must be developed. One possible method is based upon the birefringence under UV radiation of the 280 nm wavelength of lignin phenyl 189 groups which are attached tc different sides cf the hemicellulose unit crystal.
Such a techniques has not yet been developed, but if successful, should prove a reliable method for studying the entire lignin concentration variations across a whole clarinet reed, without having to section the material.
Chemistry* and Material Properties
With this basic understanding of the three major chemical components of the clarinet reed finished, the next step is to consider the natural progression to the bulk material properties of the reed, i.e., how the molecular building blocks mentioned in this chapter affect such properties as damping, modulus of elasticity, water capacity, etc., of the reed. Since these topics form a separate body of material, we shall consider them in the next chapter. 190
Endnotes
1. James A. Richards, Jr., Francis Weston Sears, M. Russell Wehr, and Mark. W. Zemansky, Modern University Physics (Reading Mass., Addison-Wesiey, 1964): 807.
2. For and excellent discussion of nomenclature, see, R. D. Guthrie,introduction to Carbohydrate Chemistry, 4th ed. (Oxford, England: Clarendon Press, 1974).
3. Guthrie, ...Carbohydrate Chemistry..., 9.
4.Eero Sjostrom, Wood Chemistry: fundamentals and applications (New york. Academic press, 1981).
5. Purdue, “Arundo...”, 392.
6. Fengel and Wegener, Wood..., 84.
7. Alvin Hudson and Rex Nelson, University Physics (New York: Harcourt Brace and Jovanovich, 1982): 839.
8. M. L .Nelson and R. T. O’Connor, “Relation of Certain Infrared Bands to Cellulose Crystallinity and Crystal Lattice Type. Part II. A New Infrared Ratio for Estimation of Crystallinity in Cellulose I and II,” Journal of Applied Polymer Science 8: 1325-1341; “Relation of Certain Infrared Bands to Cellulose Crystallinity and Crystal Lattice Type. Part I. Spectra of lattice Types I, II, and III and Amorphous Cellulose,” Journal of Applied Polymer Science 8: 1311-1324;
9. Panel discussion at the San Franscico meeting of the Material Research Society, April, 1994.
10. Nelson and O’Connor, "Infrared Bands...Part II,” 1336.
11. ibid.,1336
12. Fenger and Wegener, Wood..., 109.
13. Karl Niklas, Plant Biomechanics: an Engineering Approach to Plant Form and Function (Chicago: University of Chicago Press, 1992): 245 ff. 191
14. ibid., 247 ff.
15. Jean-Paul Joseleau and Fernand Bernoud, “Hemiceiluloses ofArundo donax at Different Stages of Maturity,” Phytochemistry, 14 (1975): 71
16. Fenger and Wegener, Wood..., I l l
17. 8. Soiomon, G. H. Rozmarin, and Cr. Simioneseu, “Etude Chemique des hemiceiluloses du Roseau. I. Separation et Fractionnement des Hemicelluloses,”Ce//u/oseChemistry and Technology, 2 (1968): 291-304.
18. Joseleau et al., “Hemiceiluloses...," 72.
19. ibid., 72.
20. ibid, 72.
21. Fenger and Wegener, Wood...,113.
22. ibid. 114.
23. ibid. 321.
24. ibid. 323
25. R. H. Marchessault and C. Y. Liang,"The Infrared Spectra pf Crystalline Polysaccharides VIII. Xylans.” Journal of Polymer Science 59 (1962): 357-372.
26. Fenger and Wegener, Wood..., 149.
27. Friedrich Emil Brauns and Dorothy Alexandra Brauns, Chemistry of Lignin, suppliment volume, covering the literature for the years 1949-1958 (N.Y. Academic Press, 1960).
28. Fenger and Wegener, Wood..., 150.
29. ibid. 142.
30. Diesheng Tai, Weixin Oho, and Wenlan Xi, “Studies ofArundo donax Lignins," 4th International Symposium on Wood and Pulping Chemistry (Paris: Jacques Poncet Bresson, 1987): 13-17. 192
31. Jean-Paul Joseleau, Gerhard E. Miksche and Seiichi Yasuda, “Structural Variation of Arundo donax in Relationship to Growth," Holzforshunsg 31 no. 1 (1976): 19-20.
32. Fenger and Wegener, Wood..., 157.
33. ibid. 161.
34. See, Tsuboi Masamichu,"Infrared Spectrum and Crystal Structure of Cellulose,” Journal of Polymer Science, 25(1957): 159-171; C. Y. Liang and R. H. Marchessault, “The Infrared Spectrum of Crystalline Polysacchrides, Ill-Native Cellulose in the Region from 640 to 1700 cm Journal of Polymer Science 34 (1959): 269-278; N.L. Nikitin, Chemistry of Cellulose and Wood (Jerusalem: Israel Program for Scientific Translations, 1966): 58-59, Ward Pigman and Derek Horton, eds.. The Carbohydrates: chemistry and biochemistry (New York: Academic Press, 1980): 1400; R. H. Marchessault and C. Y. Liang,"The Infrared Spectra pf Crystalline Polysaccharides VIII. Xylans.” Journal of Polymer Science 59 (1962): 357-372; Friedrich Emil Brauns and Dorothy Alexandra Brauns, Chemistry of Lignin, suppliment volume, covering the literature for the years 1949-1958 (N.Y. Academic Press, 1960).
35. Fengel and Wegener, Wood..., 163.
36. Tai, et al., “Studies of Arundo donax...," 16.
37. Joseleau et al., “Structural Variation...," 18.
38. Purdue, “Arundo donax," 392.
39. Fenger and Wegener, Wood..., 228. Chapter IV
Clarinet Reed Material Properties
Introduction
Given a basic understanding of the molecular components ofArundo donax, we now turn to a consideration of some of the bulk mesoscopic properties of the processed plant material. It is these properties which most affect the clarinet reed in terms of its mechanical responses.
In this chapter we summarize the results of empirical tests made to determine some of the more elementary material properties of Arundo donax in the form of processed clarinet reeds. Where possible, we also relate these properties to reed quaiity.
In order to have a valid test set, as mentioned in chapter one, a series of tests were performed on an experimental set of 80 reeds, which we shall abbreviate as {R}, consisting of fifty Vandoren V12 reeds (of which forty were strength 4, and ten were of strength 3 1/2), ten Biack Master brand reeds (Vandoren Reed
Co.) of strength 3 1/2, ten Olivieri tempered brand reeds (Olivieri Co.) of strength 4, and ten Grand Concert brand reeds (Rico Reed Co.) of thick blank and strength 4. In designing this expérimentai set of reeds, two different subsets were intended to be created-an intrabrand test set, consisting of the
193 194
forty Vandoren reeds of strength 4, and an interbrand set, consisting of the
Black Master, Olivieri, Grand Concert, and Vandoren (strength 3 1/2) reeds.
The first subset of Vandoren V I2 strength 4 reeds, which we call subset,
R2.intra, allowed for the ratings and variables within a single brand to be
compared, while the second subset of different reed types and strengths, which
we call subset R2.lnter, allowed for the ratings and variables between brands
to be compared. There were forty reeds in each subset. In large measure, the
results of the quality and performance criteria ratings were independent of
brand, while the structural measurements, which we shall describe later, varied
greatly, and showed some interesting trends. Because of the independence of the quaiity and performance criteria to brand , to reduce the amount of graphs
and statistics (which could grow quite large, otherwise), the author will present, where possible, only the results of the composite set {R} of eighty reeds. The structural statistics will be dealt with in chapter five.
Admittedly, other reed brands should have been included, such as Glotin brand reeds, and Queen brand reeds, but the brands included in the test set were those actually being used by the members of the clarinet section of The
Ohio State University Concert Band at the time of the tests, and seemed to be a balanced, although not thorough, representation of the distribution of brands of
reeds used by students throughout the country. The author produced the experimental set by asking the players their particular brand and strength, and then supplying each of them with a test box and a free box as a remuneration for participation in the testing. Overall, ten students rated reeds, and the set {R} 195 of eight boxes of reeds was selected before actual rating started to create the two subsets mentioned above. The two other student's reeds were used primarily as additional data In testing the correlation between various physical parameters, although, where appropriate their quality reports were added to the overall test set, {R} when the maintenance of the subset structure was unimportant.
The reeds were rated on a one to seven scale, since It was determined that such a rating scale best conformed to standard statistical measurement practices for human judgment tests. The reeds were rated by students ranging
In experience from advanced college undergraduates to doctoral candidates In clarinet performance. The rated Items were (In the following listed pairs, the descriptor associated with the rating of one Is listed first, while the descriptor at the other end of the scale at seven Is listed secondly. I.e., dark vs. bright means dark = 1 to bright = 7): 1) overall quality (i.e., bad-good), 2) dark vs. bright (I.e., timbre), 3) soft vs. hard (strength), 4) buzzy vs. fluid (noise), 5) squeaky vs. stable (stability), 6) weak-bodled vs. full-bodied (acoustic strength). A sample instruction set Is shown In appendix a.
The results were tabulated and compared to physical measurements made on each of the reeds Including shape measurements (to be described In detail
In the next chapter), measurements of volume fraction of vascular tissue, structural damping measurements, natural mode frequency measurements, and measurement of reed mass, both In Its normal hydrated state and oven dried to constant weighing. In addition, selected reeds were measured for their 196 extensional modulus of elasticity, bending modulus of elasticity, and material damping properties (mainly those reeds lying at the extremes of overall quality rating).
We shall summarize the measurements and findings individually in the sections to follow. Matters relating purely to shape theory, however, will be postponed until next chapter, where the effects of shape on reed vibration will be discussed in detail.
Since the reed material is a biological material, the range of variation in the measured properties is quite large, as to be expected (according to Niklas, these results show a scatter reminiscent of aWeibuil distribution).'' In some cases, largely due to expense and difficulty of obtaining research equipment, only a few exploratory tests of a variable could be made (such as thermal expansion and reed bending modulus). In these cases, the goal was to establish a general order of magnitude for the variables, with the realization that further testing is warranted.
Descriptive results
The reported values of the overall quality rating obtained are plotted as a function of reed number in figures 4.1 (a rating summary is also plotted). The descriptive statistics for the reed quality ratings, generated using the statistical package SYSTAT, are given in figure 4.2 (C.V. = cumulative variance, a measure useful in ANOVA statistics): 197
B M G COÜV V(3.5) B M 7
5 Q QQ-
■ee-
0 20 40 60 100 Reed Number
« 3 I O'
12 3 4 5 6 7
Rating Number for Overall Quality
Figure 4.1-Overall Ratings for {R} 198
N OF CASES 80 MINIMUM 1.000 MAXIMUM 7.000 RANGE 6.000 MEAN 4.350 VARIANCE 2.661 STANDARD DEV 1.631 STD. ERROR 0.182 SKEWNESS(GI) -0.259 KURTOSIS(G2) -0.487 SUM 348 C.V. 0.375 MEDIAN 4.000
Figure 4.2-Descriptive Statistics for Reed Quality rating
The positive bias ( mean = 4.350) in the data towards the "good" range of reed performance (48.75% of the reeds lie in the 5 to 7 “good quality” range, but only
26.25% lie in the 1 to 3 “poor quality” range, with another 25% at exactly 4) is probably due to one of three causes: 1) the reeds which were rated were high performance reeds, made for professional players. It is quite possible that the adage, “you get what you pay for,” is true in this case, 2) the players rating the reeds were among the finest student players in the country, and although it may seem that the attainment of such high levels of skill should make these clarinetists more demanding in terms of reed quality (and certainly, it does), it also allows the players to adapt more easily to the vagaries of the reed material and still obtain good results, 3) it may be that there is a minimum set of parameter values which will permit a reed to respond in a high quality and a 199 student quality manner (in fact, in chapter five, we shali argue this exact point), and that, by trial and error (assisted by the concomitant refinement of mouthpieces) these parameters have been understood by the reed companies in a general way. Thus, the overall higher than average ratings of the reeds in the experimental set may be a testimonial to the intuitive and empirical understanding of the reed makers themseives.
The five different performance criteria also show interesting statistics. The reported ratings and distributions are piotted in figures 4.3 to 4.7. The summary statistics are given below (figure 4.8). The pair abbreviations are DA-BR =
Dark-Bright, SO-HA = Soft-Hard, BU-FL = Buzzy-Fluid, SQ-ST =
Squeaky-Stable, WE-FU = Weak-Bodied-Full-bodied, where the first pair member is at the lower end of the scale. The names of the statistical measures
are abbreviated where possible to conserve space. The reason for the slightly larger number of cases for some of the statistical measures is that data from an additional student (Vandoren Biack Master strength 3 1/2) were included where possible.
The ratings show that in a random sampling of high performance clarinet reeds, the reedsare more than likely to be; 1) generally playable, 2) bright sounding, 3) slightly hard, 4) slightly more fluid in response, 5) slightly more stable in general, and 6) full sounding.
A Pearson correlation matrix was created in order to test the correlation between the performance descriptors with the overall reed ratings. The results are summarized in figure 4.9. BMGC Oliv BM 2.00 8
6 000- 0
0 X 3 OOO o o o ■e-e- CD- 0( >■ - QO o» L mI 4 03 03 O QD w u 3 0 0 0 ' O O □O OO00 n û
2 ■Œ - 0-0 o o q>-
0 0 20 40 60 80 100
Reed Numbers
2 3 4 5 6
Rating Number for Dark-Bright
Figure 4.3-Timbre Ratings for {R} B MGC Oliv VT3.51 B M 2 0 1 8
6 ■Q~ ■(D-QQ QQ" q j I Q Q "2 I? ? 4 (DO ( 30- ■0— 0 4 [D w ■O-OCD 2 0 0 20 40 60 80 100 Reed Number 19 > «r I 2 3 4 5 6 Rating Number for Soft-Hard Figure 4.4-Strength Ratings for {R} BM G C Oliv VT3.51 BM 2 0 2 8 6 e» Q- oc OQQ-O 4 - J- Q Q Q & 2 ■ ^ ■ O O Q ■œ 0 0 20 40 60 80 100 Reed Number 3 4 5 Rating Number for Buzzy-Fluid Figure 4.5-Noise Ratings for {R} BMGC Oliv 8 203 7 6 (D an >QQ a e —o ù Of 5 ■ee- ? 4 3 1 0 0 20 40 60 80 100 Reed Number & 5 ; O" 41 L 3 4 5 6 7 Rating Number for Squeaky-Stable Figure 4.6-Stability Ratings for {R} VWoren, V 12 (4) BM GC O liv V{3 .5) BM 204 ■a Q C» - C ' 20 40 60 80 100 4» 5 y b.L 12 3 4 5 6 7 Rating Number for Veak-Full Figure 4.7-Projection Strength Ratings for {R} 205 QUAL DA-BR SO-HA BU-FL SQ-ST WE-FU CASES 80 80 90 90 90 80 MINIMU 1.000 1.000 1.000 1.000 2.000 1.000 MAXIMU 7.000 7.000 7.000 7.000 7.000 7.000 RANGE 6.000 6.000 6.000 6.000 5.000 6.000 MEAN 4.350 4.050 4.556 4.189 4.756 4.200 VARIANC 2.661 1.947 • 1.800 2.627 1.917 1.858 ST. DEV 1.631 1.395 1.342 1.621 1.385 1.363 STD. ER 0.182 0.156 0.141 0.171 0.146 0.152 SKEW -0.259 -0.146 •0.077 -0.149 -0.245 -0.064 KURTO -0.487 -0.843 -0.590 -0.805 -0.928 -0.398 SUM 348 324 410 377 428 336 C.V. 0.375 0.345 0.295 0.387 0.291 0.325 MED 4.000 4.000 4.500 4.000 5.000 4.000 Figure 4.8-Summary Statistics for {R} QUAL DA-BR SO-HA BU-FL SQ-ST WE-FU QUAL 1.000 DA-BR -0.399 1.000 SO-HA -0.131 -0.284 1.000 BU-FL 0.623 -0.298 ■ -0.011 1.000 SQ-ST 0.455 -0.102 0.019 0.431 1.000 WE-FU 0.731 -0.593 0.092 0.534 0.309 1.000 NUMBER QF OBSERVATIONS: 70 Figure 4.9-Pearson Correlation Matrix for Performance Descriptor 206 As a rule of thumb, a .7 (or 70%) correlation coefficient is accepted as a threshold for true correlation in the physical sciences. The soft sciences accept lower thresholds (we have seen some psychologists present data claiming that .3 correlation coefficients are evidence of correlation!). In this document, since the reed material is of biological origin, we shall not be bound so closely to the exact correlation threshold requirements of the physical sciences, but we shall not be so loose as to generate vague associations. We shall hold to the requirement that a .5 correlation coefficient is the minimum threshold for true correlation in this document. Under this criteria, the correlation matrix given above is particularly interesting. There appears to be a mild correlation (-.399) between the timbre of a reed and its rating. Since there is a negative sign, this implies the correlation is the lower the DA-BR value (i.e., the darker the reed), the higher the quality rating. There is no significant correlation between reed strength and rating, although there is a slight trend to associate harder reeds with higher rating. The strong correlations of the last three descriptors indicates that whatever psychological processes are used to arrive at a rating for a clarinet reed, these three descriptors are given high significance. The degrees of buzziness of the reed is over the threshold for true correlation, which means that it is likely that if a reed sounds buzzy, it is automatically given a lower rating. This is interesting, in that, because of reed shape differences, high performance reeds are less prone to asymmetric torsional motion (the principle cause of reed buzz) than student quality reeds. It is the correlation between buzziness and rating, and 207 not the quality of cane, which is why these reeds are regarded as inferior. Reed buzz is primarily a function of transverse (side-to-side) structural factors, as we shall show in chapter five. Squeakiness, excluding the sudden loss of lip damping (as expiained in chapter five), is primarily a function of longitudinal (lengthwise) structural factors. It also shows a strong, but slightly smaller correlation with reed quality. The more stable (less likely to squeak) a reed sounds, the more highly rated it is. It is amazing that this correlation isn’t higher, but since the mean is of the stability pair descriptor is so skewed towards “stable” in the test set, there probably were not enough squeak-prone reeds to see the correlation fully. The depth of the sound produced by a reeds is the most highly correlated of all of the performance descriptors with reed quality. The correlation coefficient is over the .7, which is the threshold for meaningfulness the physical sciences. This means that, in any given population of reeds, the most highly prized property of a reed is its ability to sound full throughout the range. Unfortunately, although there are some interesting one-dimensional theories, there is no clear understanding of the coupling of reed acoustics to air column acoustics (chapter five). The problem is complicated by the existence of a mouthpiece, whose design invites highly non-linear fluid mechanical responses. We shall outline the problem in chapter five and offer a partial solution. In terms of the relationship between descriptors, we note two. There is a negative correlation between brightness and fullness of sound (meaning a darker sound is correlated with a fuller sound) and a positive correlation 208 between a fluid sound and a full sound. Apparently, the same process which leads to a fluid sound also allows for a larger power output from the reed (probably fewer energetic loss factors, such as higher degrees of freedom, i.e., energy being siphoned into torsional modes, friction, etc.). Since the last three descriptors are so highly correlated with reed quality, we may ask if there is an equation which will allow one to predict the reed quality from a measurement of these descriptors. If we assume a simple linear regression model: QUALITY = a [BU-FL] + p [SQ-ST] + Ô [WE-FU] + E (4.1) then a least-squares fit of the data gives the coefficients: a = .265,a = .203, a = .652, a = -.398, with an R2 = .635. The fit is not so good as we should like(R2 = .635), but it is a beginning in delimiting the actual (and perhaps intuitive) criteria people use to rate reeds. Mass/Weight Properties Density is defined as the amount of mass (usually, kilograms, kg, in the System system of measurement), per some unit volume (usually, cubic meters, m3, in the S.i. system): p= m / V (4.2) 209 By taking a small parallelplped of clarinet reed material and measuring its weight using a microbalance, a representative density of the reed material was computed to be 461 kg/m 3. In the older, but still used cgs system, this is 0.461 g /c m 3 . Summerfeld arrived at a slightly higher value of 0.5 g/cm 3, although he probably used only an approximation for his work. Bamboo, by contrast has a much higher density of 660 kg/m 3, although the extensional modulus in the plane of the vascular tissue is in the same range asArundo donax. This moderate density yet high modulus ( for a plant material) may account for some of the characteristics which makesArundo donax unique as a reed material.2 The empirical value quoted above is obviously representative of the plant material on the average because of the effects of: 1 ) material inhomogeneity (i.e., different cell types are in different concentrations in different regions of the material), 2) pressure and temperature dependency (these measurements were made at ambient room temperature (= 24 °C) and ambient pressure (= 30 mm/Hg)), 3) the age of the stem (it is impossible to tell in what stage of development the reed material was when harvested). The test was repeated with two other samples, which yielded densities of 497 kg/m3 and 412 kg/m3, respectively. To be safe, a variation of ±10% should be allowed in the total density range of the material. This may seem to be a wide variation, but given the biological nature of this material, such a range seems prudent. To study the variation of reed mass, prior to distributing the reeds to the student players to be rated, the masses of the reeds were measured on a 210 standard laboratory (Mettler) microbalance. A plot of the mass measurements for all of the reeds is shown in figure 4.10. Selected statistics are given in figures 4.11. N OF CASES 80 MINIMUM 0.682 MAXIMUM 1.018 RANGE 0.336 MEAN 0.862 (gr) VARIANCE 0.005 STANDARD DEV 0.074 STD. ERROR 0:008 SKEWNESS(GI) -0.063 KURT0SIS(G2) -0.316 SUM 68.988 C.V. 0.085 MEDIAN 0.860 (gr) Figure 4.11-Mass Statistics A breakdown of the mean by brand is ( all measurements ± .005 gr.): Vandoren V I2 (4) = .876 gr, BM = .752 gr, GC = .896 gr, Oliv = .891 gr, V I2 (3) = .856. The mass data shows some interesting variations both within and between 211 Vamdoren V12 [A] BM GC O liv V[3.5] BM 1.1 o o 1.0 0 n-f 0 0 ^ ■a o o n o <0 % « CD Ch ^ 0.9 c _ o 0 % ° ? ° % O 0 p % n ° 1 0 °o °°o° „ o o o ( > O S 0.8 (S> z 0 ° 0 <1 (1 0 % 0.6 20 40 60 80 100 Figure 4.10-Mass Measurement Summary for {R} 212 brands of reeds. The Vandoren subset shows a difference between the average mass of the two different reed strengths (3 1/2 and 4). This is significant in the reed selection process, since most reed companies, we assume, grade the strength of reeds according to tip bending resistance and not simple reed mass. The difference in reed strength(3/12 and 4) in the Vandoren sets above implies that for some reason there is a modest correlation between tip bending strength and reed mass. One may be tempted to simply conclude that whatever bending tests the Vandoren reeds were put through to grade them simply discriminated between thicker and thinner reed tips, thus accounting for the greater mass of the strength 4 reeds; however, this assumption would be wrong, as the Vandoren 3/12 strength reeds in S2 show almost identical mean tip thickness as those of strength 4 (strength 3 1/2 = .135+ .013 mm, strength 4 = .134 ± .009 mm). In fact, a large portion of the mass difference comes not from the tip, but from a slightly thicker midsection for the strength 4 reeds (that the heel thickness is not a contributing factor is reflected by the fact that the heel thickness of the two strengths are virtually identical: strength 4 = 3.136 mm, strength 3 1/2 = 3.138 mm). For strength 3 1/2 reeds the midsection (measured in the center at 16 mm from the tip) thickness is 1.114 mm, while for strength 4 it is 1.346 mm. It is probable that it is the increase in midplane bending resistance of the thicker strength 4 midsection which largely accounts for the difference in reed strength rating. Such a large thickness difference in the midsection also is much more 213 likely to account for the mass variation seen between the two strengths than a tip thickness difference might. The interbrand mass differences are also striking. The Black Master reed set, having a 3 mm shorter length, is correspondingly lighter in mass (.752 ± .047 gr). In fact, all of the Vandoren reeds are lighter than any of the other reed brands measured. This difference may be accounted for simply by thicker heels, etc. in the other reeds. A Pearson reduced correlation matrix of the mass to quality rating descriptors is given in figure 4. 12. The complete matrix of coefficients is not given because the descriptor coefficients are given in the submatrix in figure 4.10. Mass Mass 1.000 Qual -0 .1 4 2 DA-BR 0.190 SO-HA -0.131 BU-FL -0.2 7 6 SQ-ST 0.068 WE-FU -0 .0 8 7 Figure 4.12-Mass and Quality Descriptor Correlation Matrix There is, apparently, no significant correlation between the mass of a previously unused reed and the quality of that reed. The modest negative correlation with mass and buzziness is intriguing and complicated to explain (we shall do so in chapter five). 214 So far, we have talked almost exclusively about mass, when we would really like to include information about reed density, especially as it changes over the reed surface, due to different amounts of vascular tissue in different regions. The problem is that due to the irregular shape of the reed, it is difficult to measure density of the reed precisely for any given reed, let alone portions of the reed. In an attempt to grapple with this matter, the author was led to the Campus Electron Optical Facility in the medical school at The Ohio State University (the author is grateful to Dr. Richard Swenson in the department of zoology for this suggestion). At this facility there is an optical densitometer, which is a device used in engineering, primarily, to measure density variations on the surface of a metal. We have'adapted it here to look at density variations on the reed surface. The idea is that light passes through a material based upon the density of the material, so that a recording of the percent transmission of light through the material should correlate with the thickness or local density of the material. In the case of a metal, one substitutes electrons passing through the metal and uses, instead of an optical sensor, as we used, an electron detector. Both techniques are handles by the same computer program. We used light because this allowed one to see the sample, and required nothing more than a specialized camera and video detection equipment. A sample optical densitometry plot is shown in figure 4.13.3 The plot, of an oboe reed, shows the unmistakable density variations induced by scraping the reed. The blow-up of 2 1 5 Figure 4.13-Contour Optical Density Map of Oboe and Clarinet Reed 216 the tip of a clarinet reed in figure 4.14 shows a very light transparent vascular bundle. The computer also allowed for cross-sections along a line to be plotted. In figure 4.15 we show such a cross-section. In this case, the vascular bundles are quite easy to pick out as the depressed areas of the graph (= lower transmission values). The reason that this technology cannot be used to quantitatively study density variations within a reed, however, is that while there is a linear relationship between density and light (electron) transmission in metals, the exact relationship between light transmissibility and the reed material is unknown, and expected to be nonlinear. In addition, the signal to noise ratio is quite low, resulting in the vascular tissue, which is darker than surrounding tissue, looking much thicker than surrounding tissue, when in fact it is merely darker (due to greater lignification). These considerations, plus problems with scattering and internal reflectance, introduce errors which make this a method for qualitative use only. Nevertheless, as a pedagogical tool for teaching scraping techniques, it is unrivaled, as the plot of the oboe reed suggests. Effects of Heat on the Clarinet Reed Many external agents, such as heat, light, and oral environment attack the clarinet reed over time, and it is worth spending some time examining some of these activities. There are many folktales associated with the effects of these agents, as we shall point out, and hopefully the information presented in this 2 1 7 : DMEl Int:18 Artt:B,8 512,512 . Gfi£Y: 512 HAG r Ix CflH N T = 8 SCALE 1:1.5234 ? g : :'0 Hoii«: zooa ptn zoom doun up Figure 4.14-Optical Density Map of a Clarinet Reed Tip 2 1 8 Figure 4.15-Cross-sectional Optical Density 219 section will help to correct the material passed on from teacher to pupil about the preservation of reeds. Heat, within the normal physiological (32-37 oC) and ambient temperature ranges has almost no deleterious effects on the normal clarinet reed matrix. The results of both TGA (recounted in chapter three) and TMA (Thermal Mechanical Analysis, see below) tests show that there is little or no measurable chemical degradation and nominal dimensional changes of the reed material within this temperature range. Temperatures in more "hostile" environments do have pronounced effects on both the dimensional stability of the reed and the chemical integrity of the reed matrix. Elevated temperatures within the range of 40 oC-100 °C are the most common temperatures normally encountered by clarinetists in the course of deliberate reed work (such as in scraping and filing the reed, which can induce thermal hot spots on the back side of the reed well over 50 °C due to friction, or as in soaking the reed in nearly boiling water to clean the reed). If the heating is done while wet instead of dry, studies on wood reported by Fenger and Wegener imply (and we assume that the same qualitative behavior applies to Arundo donax) that the cellulose matrix, instead of decrystallizing, will actually recrystallize, and the percent crystallization will be prevented from decreasing as in the case of heating dry wood.4 In addition, the presence of water will prevent chain-splitting or "scissoring" (i.e., cutting) of the cellulose polymer within the range of 120 oC-160 oC, thus preventing chemical breakdown. Beyond these temperatures, the cellulose begins to decompose 220 into elementary furans, becoming amorphous in structure. While lignin in wood is generally stable to 200 oC, nevertheless, the hydrogen bonds which are loosely attached to the molecule begin to breakdown at 60 °C-80 °C, and between 100 oC-180 oC the aromatic quality of the molecule is lost.s In addition, lignin softens in this temperature range (bamboo lignin, for instance, which is surely similar to that of Arundo donax, softens at 162 oC).6 Heat in this hostile temperature range also has profound effects on the dimensional properties of the reed material. A material property, the coefficient of thermal expansion, is defined as the volume change per unit degree of temperature change of the material, and measures these effects: a = 1/V(aV/3T)p (4.3) In order to measure the coefficient of thermal expansion in the various axes of the processed plant material, small samples of rectangular cross-section (approximately, 5 mm in length) were excised from several clarinet reeds and submitted to Dr. James Culbertson of the Ohio State University department of dentistry and his postdoctoral assistant. Dr. Alka Thakur, for testing. The reed samples were cut from different orientations of the reed material, so that the affect of temperature on the expansion of each of the three standard material plane (L, R, and I , see below for nomenclature) could be studied. A word needs to be said about the natural axis in cylindrical plant stems. Engineers identify three such axes (unfortunately, botanists use a different 221 scheme using similar names, and it is often confusing to know which is which): 1) the longitudinal axis which is parallel to the direction of growth, 2) the radial axis, which is directed inward, in the direction one might push the long end of a razor blade from outside of the epidermis (in the direction of elongation) to the inner, soft tissue, 3) thetangential axis, which is the axis one exposes when the top is cut off of the stem. These orientations are summarized in figure 4.16. A computer-controlled test device called a thermomechanical analyzer (Du Pont TMA 2940 Thermal Mechanical Analyzer), which measures the change in length of a sample (in microns) with increasing temperature, was used to determine the thermal expansion curves as a function of temperature. The results are presented in figure 4.17. Unfortunately, during the test, we used the biological instead of the engineering axis nomenclature, so that the plots are in biological nomenclature and the results below are in engineering nomenclature. The correspondence is: transverse(b) = longitudinal(e), tangential(b) = radial(e), and radial(b) = transverse(e). The expansion coefficients (engineering nomenclature) at room temperature in the physiological temperature range (25 oC to 35 °C) for the three axes are: Longitudinal 18.3 pm/m oC (-7.90pm/m oC) Radial 33.5pm/m oC Transverse 65.2pm/m oC Figure 4.18-Coefficents of Thermal Expansion for Arundo donax The longitudinal, radial and transverse directions all show expansion upon 222 Fiber / Longitudi nal Radial Tangential (note; the TMAsampiea usethe biological nomenclature instead of engineering, ao that longitudinal = tangential, radial = radial, and transverse = tangential) Figure 4.16-Stem Orientation 2 23 Sample: REED-TRANSVERSE F ile : C: REEO l.007 sue: 3.1710 mm TMA O p e ra to r: ALKA THAKUR M ethod: TMA FOR REED SAMPLE Run D a te: 1 4 -A g r-9 5 18: 27 Comment: THICK SAMPLE oH 4 1 .5 8 % o— 8.01pm/ffl*C I 5 “5" - 1 0 4 -1 5 -5 0 50 100 150 200 250 Temperature (%) TMA V5.1A DuPont 2100 Figure 4.17-Thermal Expansion Curves for Arundo dona) Figure 4.17 (cent.) 2 2 4 Sample: flESD-TANGENTlAL (A) rile : C: REEDl.004 Size: 1.7300 mm TMA O p e ra to r: ALKA THAKUR M ethod: TMA FOR REED SAMPLE Run D ate: i4 -A p r- 9 5 15: 46 Comment: THICK SAMPLE 0 - - 1 0 - 1 5 0 .2 2 *0 a"-37.9pm/m*C -2 0 -5 0 50 100 ISO 200 250 Temperature (*C) TMA V5. lA DuPont 225 Figure 4.17 (cont.) Sample: RSEO-AAOIAL F i le : C: REEOl.OOG Size: 2.2130 mm TMA Operator: ALKA THAKUR Method: TMA fo r AE50 SAMPLE Run D a te : iA -A p r -9 5 17: 34 Comment: THICK SAMPLE 0 - - 1 0 - cn - 2 0 - -50 50 100 200 250 Temperature ("Cl TMA VS.lA OuPont 2100 226 heating. The radial and transverse axes, which have less structural strength (lower moduli, etc.) than the longitudinal axis, show the effects of heating to a more pronounced extent than the direction of axial growth (the longitudinal axis). This is to be expected, as heating is a form of stress, and the wood reacts as with any applied stress, showing greatest resistance to stress in the longitudinal axis. The interesting observation here is that at physiological temperatures, Arundo donax actually undergoes a brief contraction period (for reasons which are still not clear). This value is shown in parenthesis in figure 4.18. This should not be interpreted to mean that the material actually contracts inside a players oral cavity, because the expansion induced by hydration due to saliva more than compensates for the small contraction seen due to thermal effects. All three graphs show the same characteristic three regions of activity from 0 oC to 250 OC. In region one, approximately 0 oQ to 50 oQ, the material expands roughly linearly as many other materials do. In region 2, approximately 50 oQ to 150 oQ, the material loses water of cellular hydration, and begins to shrink. Each axis shows a drop of about 13 pm in size, which amounts to a .4 % (L), .75 % (R), and .63 % (T) for each of the three axis. In region three, approximately 150 oQ to 250 OQ, the water had been removed, and the hemicelluloses begin to break down into elementary furans. The removal of that amount of hydrogen bonding which was due to the presence of water allows the cellulose/lignin lattice to re-expand outward a bit. Consequentially, the material begins to expand at a rather rapid rate. 227 The mechanical properties of Arundo donax change in response to heat. Bodig and Jayne suggest that the effect of a moderate (± 100 oC) change of temperature on the moduli of elasticity is to cause them to decrease for increasing temperature and decrease for decreasing temperature.^ This relationship may be expressed, in many cases, by a simple linear equation of the form: (E or G),2 = (E or G)ti [1+ (3i,n (t2-tl)] (4.4) where E and G are the extensional and bending moduli, respectively at either the higher ( subscript, t2) or lower (subscript, t1) temperature in Celsius, and Bn is an empirical coefficient for each of the different types of moduli and their assooiated directions: 1 = extensional, 2 = bending, in each of the different directions, n= L, R, T. Ba.L, for instance is the constant which measures the change in bending modulus in the longitudinal direction. Typical values of B are on the order of .001 to .01 (mostly near .001), and the sign is negative, since the effect is to decrease the original modulus value with increasing temperature. Using this equation, it is easy to see from the data supplied by Bodig and Jayne for wood (and we assume that the range of values is roughly the same for Arundo donax) that the temperature change from ambient room temperature (20 oQ) to oral cavity temperature (37 oQ) causes at most a 17% change in the tangential modulus, and only a 5% or less change in the modulus in the longitudinal direction. By contrast, the effeot of water causes changes almost five times as great. 228 The Effects of Light on the Clarinet Reed Light in the visible range of the spectrum induces color changes in plant material, which is dependent upon the moisture, temperature and chemical components (nitrogen, etc.) of the atmosphere. Arundo donax, as mentioned in chapter one, changes from a green to a golden color due to the conversion of chlorophyll (green colored) to a different chromophore (a chormophore is a color generating compound), probably xanthophyll. Most reed growers strive to achieve a golden yellow color in the sunning process. The precise colorimetric changes may be monitored by UV-Visible spectroscopy, although the author has not done so, since this would require cultivating reed material. It is not obvious if reed color by itself is a good indicator of reed quality. Since the reed color may be precisely determined by the UV-Visible spectroscopic methods mentioned in chapter three, at least the interior material color (the epidermis color is variable due to the presence of tannin), it is possible to test this hypothesis with actual clarinet reeds. This is an experiment which still needs to be done. In the case of wood, the penetration of UV radiation is only 75 |im and 200pm for visible light.s If this is also true forArundo donax (a permissible extrapolation, we expect), then this means that the tip of the clarinet reed (approximately 100pm thick) is the most vulnerable to degradation by light; however, generally either long exposure times, or high radiation levels, or special atmospheres are required to induce rapid change in the cellular 229 structure, with cell wall shrinking and microcracking the most common result. It is doubtful (although not tested) that short-term, low level radiation from light bulbs or fluorescent lights will have any significant affects on the reed cellular matrix. The effects on the ionizing radiation may be influenced by moisture content and temperature, and is a matter which needs study. With high levels of UV radiation, some changes in cellulose may occur, such as a loss in weight, a lowering of the Dp, or a change in the cellulose components (a loss of a-cellulose, for example), accompanied by the formation of many free radicals (again, we may assume that the results transfer to Arundo donax to some degree).^ The in weight loss is even more pronounced if the sample of isolated cellulose is hydrated. The presence of lignin seems to protect the cellulose matrix, however, since, lignin is ultraviolet active and preferentially absorbs the UV radiation, mainly in the chromophoric sites of the molecule, such as phenyl hydroxy groups, double bonds, and carbonyl g ro u p s .10 Again, with the relatively high lignin content of Arundo donax, one may assume that short-term exposure of ambient radiation (light bulbs, etc.) does little to damage the reed material compared, at least to many other more severe chemical effects. The Effect of Saliva on the Clarinet Reed What are the chemical effects likely to be observed in the reed/oral cavity environment? We have already speculated that the hemicellulose is gradually leached from the reed material, probably due to the alkali content of saliva. 230 Salivai pH varies depending upon the rate of salivai flow from a pH of approximately 6 (no flow, a condition known as xerostomia) to a pH of approximately 8 in full flow.n The pH is sensitive to flow rate mainly because this determines the amount of salivai bicarbonates in solution (since bicarbonates generally raise the pH into the alkaline levels in solution). The faster the flow rate, the more bicarbonates are delivered into the saliva stream. Since saliva pH is dependent upon flow rate, several observations are possible. In the course of a concert, if one suffers from dry mouth (xerostomia), the salivai pH is expected to be below 7, and be therefore, acidic. A complex buffering system in saliva, again, partially due to the presence of bicarbonates, keeps mouth pH from falling below 6 and eating though the oral cavity. Since the least change for the reed is probably induced in the pH range of neutral water (pH 7), perhaps using a salivai flow stimulant at concerts would help increase reed life. Nervousness, often induced by concert playing, besides leading to xerostomia, may also lead to rapid breathing, which tends to flush CO2 out of the system, producing a condition called respiratory alkalosis (whereas holding one's breath leads to an increase in CO2 and respiratory acidosis). The drop in CO2 reduces the amount of available bicarbonates (which are synthesized from carbon dioxide), lowering the saliva pH. By contrast, during a rehearsal, when a player is salivating and also partially holding their breath ( increasing the amount of CO2) during the course of playing, the saliva pH is expected to be slightly alkaline. Thus, the mouth pH 231 varies considerably during the playing life of a typical clarinet reed. One would expect, on average, that rehearsal conditions would be encountered more frequently than concerts, so that the mouth pH stays slightly alkaline most of the time (the author has never had the chance to test this hypothesis, but based on the arguments presented above, it seems plausible). This slight degree of alkalinity probably enhances the leaching of hemicellulose from the reed matrix (hemicelluloses are soluable in mild alkali solutions). The affect of these changes in pH on the cellulose matrix and lignin is relatively slight. As pointed out earlier, of more importance than simple saliva pH are the contaminants in saliva which infuse into the reed matrix. The presence of amines in the infrared spectra of spent reeds indicates the presence of epithelial cells from the mouth as well as glycoproteins contained in saliva: salivary mucosins (MG1, MG2), Proline-rich Glycoproteins (PRG), a-amylases (a-Am), peroxidase (Px), Carbonic Anhydrase (Anh), Fucose-rich glycoproteins (FRG), Immunoglobulin (IgA), Kallikrein (KIk), Lactoferrin (Lf) and Fibronectrin ( F n ) .i2 Several other chemical barriers to water absorption, in addition to the loss of absorption due to the decrease in hemicelluloses, are created due to the evaporation of saliva on the reed surface. The existence of hydrophobic (water avoiding) pockets in MG1 (mucin glycoprotein 1) has been demonstrated, and is one such barrier (playing on a reed while having a cold which causes a great deal of mucous discharge from the throat and lungs, will very quickly render a reed less waterabsorbing).13 232 In addition, oral bacteria quickly remove the sugar containing elements of the glycoproteins of saliva once it leaves the mouth and rests on the reed surface (the bacteria themselves are yet another source of reed deterioration to be discussed momentarily).The removal of sugars from saliva results in a protein precipitate which is rich in calcium and of low solubility.is Finally, a-amylase, among other glycoproteins, contains significant levels of bound sialic acid, which is quickly released from the salivai solution by enzymatic hydrolysis. Once released it forms a water insoluble precipitate.16 Combined, the barrier presented by these salivary artifacts may be quite formidable, and may keep the reed from fully hydrating as it ages, resulting in higher stiffness and brittleness. Clarinet Reed Degradation The effects of heat, iight and oral environment all contribute to the breakdown of the clarinet reed. So far, the author has identified five different major routes by which the reed deteriorates over time in a typical playing situation. These breakdown pathways are summarized below. It should be pointed out that remedies or preventives potentially exist for each of these deteriorative processes, and we shall comment on each in course. To begin with, contrary to foiklore, the clarinet reed material does not wear out as it ages. A comparison of pristine and spent reeds show the same number of microcracks in the cell wall matrix of both. Under SEM no large tears were observed in either type of reed. Any mechanical degradation seems to be 233 limited to the slight decrystallization of cellulose in the reed matrix mentioned earlier. Chemical breakdown is of three types: 1) loss of hemicellulose due to alkali leaching of saliva (which, although a type of breakdown, is responsible for the “breaking in” of the clarinet reed, as mentioned in chapter three), 2) contamination of the reed due to salivai artifact (amines, glycoproteins, sialic acid, etc.). These breakdown pathways render the material, in effect, more brittle and less hydrophyllic, and, 3) in addition to leaching hemicelluoses and coating the reed, saliva contains ammonia and other alkali, and these have been shown to induce plasticization in wood. The result is that the modulus of the material falls (the reed becomes “softer”), and the damping increases (the reed does not maintain sound easily). These three process, as well as the mass increase due to the contamination of the saliva and oral microflora, change the vibrational charateristics of the reed, as we shall show in chapter five. Finally, while examining several clarinet and saxophone reeds under the scanning electron microscope, the author noticed a single strain of bacteria which lined some of the vascular tissue and parenchyma cells (figures4.19 - 4.22). The size of the bacteria proved to be on the order of one micron and was coccoidal (spherical) in shape (figure 4 .1 9 ). Heinrich points out in his dissertation on bassoon reeds that he observed a type of bacteria which infused itself into reed material as ita g e d j s The author maintains that both bacteria are the same. 2 3 4 « Figure 4.19-Shape of S. Epidermitis and its Migration in Reed Pit Cells 235 Figure 4.20-Bacterlal Deposition on Inner Xylem Wall 236 Figure 4.21-Bacterial Biomass 237 00^5 15KU X6,0I00 tN«i WD14 Figure 4.22-Bacterial Sheet (Heinrich’s “Fungus”) 238 Typically, the bacteria enters though the pit cells of the xylem (figure 4.19) and deposit themselves there via a glocosidic lining (figure 4.20). The bacteria grow to considerable biomass, eventually forming thick sheets on the reed (figure 4.21) which resembled a whitish coating (figure 4.22). The effect of the bacteria on the clarinet reed is three-fold: 1) it adds mass to the clarinet reed tip, 2) it reduces the range of motion of the torsional and bending modes, and 3) it changes the overall shape of the reed tip. Contrary to Heinrich’s assertion, this particular bacteria does not harvest the reed matter for food (it is one of the types of bacteria which gets its nutrients through the extraction of sugars in saliva, as we mentioned earlier), and so the degradation caused by the reed is on the physical response of the reed and not on the material itself. This bacteria has been identified for the author by pathologist Dr. Leona Ayres of The Ohio Sate University Hospitals/department of Medicine. She did several detailed wipes of both pristine and spent reeds in order to recover and culture bacteria for identification. The pristine reeds were almost entirely bacteria-free (to the relief of the author and reed players everywhere), or contained a small number of harmless and non-growing bacteria, at least one of them being of a soil-borne variety, as the author had suspected. The pristine reeds also showed minute traces of some common oral microflora. None of these bacteria either grow in or interact with the reed matrix. By far the largest bacteria type present, and the identity of the bacteria which the author found in the SEM study (and we suspect of Heinrich’s as weil) is 239 Staphalocccus Epidermitis -the common bacteria found, as the name implies, on the mouth and hands of virtually everyone (the bacteria is innocuous). Only this type of bacteria is of any consequence in the breakdown of the clarinet reed vibrational life, as no other common bacteria grows under typical playing conditions. As mentioned above, S. Epidermitis is one of the bacteria which removes the sugars from saliva (causing the deposition of sialic acid as a by-product) as it feeds on these salivai nutrients. The bacteria becomes dormant without water, and so, one way to slow down the growth of the bacteria it to keep a reed cool and dry. This will not kill the bacteria, however, but only arrest their growth. Because the bacteria attach to the cell walls through a glucosidic monolayer, even if one could kill the bacteria by a strong enough preparation of alcohol or hydrogen peroxide which some players use to sterilize their reeds (preparations which themselves also harm the reed cell walls), neither would fracture the glucosidic monolayer. The result would be a collection of dead bacteria within the reed, with more to appear with each new use. The end result is no gain for the player. What is needed is either a bacterial resistant coating for the reed or an antibacteria agent which is non-alcohol based. Fortunately, both of these already exist or soon will, and only need to be developed. Towards the Prevention of Reed Degradation There is little one can do to salvage a reed once salivai glycoproteins and bacteria have been deposited. Prevention is therefore the best alternative. 240 A water-based antibacterial rinse for the reed is needed (alcohol rinses may cause dehydration of the cell wall matrix). Dr. Ayers, mentioned above, and the author have such a candidate (this candidate is a rinse already currently on the market, but which requires a prescription), which not only kills the bacterial, but breaks the monolayer attaching the bacteria to the reed. As the rinse must be made in non-prescription strength, and pass an FDA review, no further comment on its effectivness is warrented in this document. Our purpose here is merely to state the nature of a proper solution to the bacterial contamination problem, in contrast to home remedies currently being used by some players. We have not tested commercial preparations made specifically for reeds, and cannot comment on their effectiveness, although, from what the author has been told of them, most do hot appear to deal with the bacterial attachment problem. The second method to prevent reed degradation is a rather novel approach, which, if successful, should be a great help to the clarinet community. Certain polymers exist as solids at room temperature and pressure, but are such that at slightly elevated temperature quickly enter the gas phase. By placing a material in a chamber and introducing the polymer in the gas phase, the polymer may be caused to coat the material (this process is called gas phase infiltration). Heart valves and electronic components are coated in this way. A particularly inert polymer, parylene, has the above properties and is often used for gas phase deposition of material, such as heart valves and rare books (in fact, the United States Library of Congress uses this polymer to coat its rare 241 books).19 Because the material is deposited as a gas, the thickness deposited is quite small (about lOpm). It is virtually invisible, impervious to mild chemical and bacterial attacks, and already has the approval of the FDA. In the author’s opinion, this polymer material has the potential to change the reed industry, since the reed remains somewhat water absorbing, yet chemically inert. Since it is applied in a large chamber, it may be applied to a bulk quantity reeds at one time. The only thing not known at the present time is the amount of material which may be deposited without changing the reed vibrational characteristics, but it is hoped that such research will be finished soon. The only current proper retardant for reed degradation other than those still experimental ones mentioned above (and excluding some commercial preparations for double reeds mentioned above which the author has not had the advantage of testing and whose effectiveness is unknown) is to keep the reed in a cool, dry place, such as a refrigerator (not a freezer) if condensation is not a problem, otherwise on a cool, dry shelf or reed holder with a desiccant (calcium sulfate, for example). Until more modern solutions have been perfected and researched, current rinses and ultrasound treatments, etc. should not be expected to restore a spent reed, nor prevent degradation. Reed Hvdroscopic Properties The clarinet reed is rarely played in a dry state. Since the amount of water saturation in the cell wall matrix when the reed in the oral cavity is quite high. 242 the influence of water and saliva on the reed structure is crucial in understanding the subsequent vibrational characteristics of the clarinet reed. There are two types of water typically stored in a clarinet reed: 1) the water of hydration of the cell wall matrix, i.e., the more or less permanent water which is bound to the cellulose-hemicellulose-lignin matrix (this is called, after Bodig, bound water) and 2) the ephemeral water loading within the cellular cavities and vascular tissue capillaries during salivai hydration during playing (this is called, free w a te r ) .20 In order to determine the amount of water bound to the cell wall matrix, thirty reeds in {R} were oven dried using an oven at 110 oC in the Department of Chemistry at The Ohio State University for two hours (the author especially thanks Ruth Anderson, who is in charge of the undergraduate analytical laboratory for her help). Ten of these reeds, in addition, were further heated overnight at 60 °C oven to make sure that the original two hour drying was sufficient to reach a constant reproducible dry weight (it was, as the weights measured overnight and after the first two hours were virtually identical). The reeds were weighed before drying, and after drying. A plot of the masses in grams is shown in figure 4.23. A plot of the mass percent of bound water (the so-called water content, Gwa) is also given. The average of the Gwa is 5.98 %. To determine the amount of free water, the author weighted three pristine reeds and then placed them in his mouth for a length time equal to that encountered during warm-up prior to playing. The reeds were not "dripping water”, but were moist, which is the condition in which most clarinet reeds are 243