f EVALUATION OF FOURIER TRANSFORM INFRARED SPECTROSCOPY FOR THE CHARACTERIZATION OF ORGANIC COMPOUNDS IN ART AND ARCHAEOLOGY by Gretchen Louise SHEARER Thesis submitted for the degree of Doctor of Philosophy in the Faculty of Science of University College London October 1989 Department of Conservation and Materials Science Institute of Archaeology University College London ProQuest Number: 10797717 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10797717 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ABSTRACT The application of Fourier transform infrared spectroscopy (FT- IR) to the characterization of materials in art and archaeology is evaluated. The diffuse reflectance accessory was used extensively and an infrared microscope was utilized for microscopic samples. The development and theory of diffuse reflectance FT-IR spectroscopy are given and a brief outline of previous use of infrared spectroscopy in archaeological and art conservation is included. The experimental procedures and sample handling used in the research are explained in detail. Diffuse reflectance spectra of several classes of organic materials available in antiquity are presented. The classes of organic materials include waxes, fats and oils, bituminous materials, resins, amber, shellac, pitch, gums and gum resins and proteins. The spectra of the reference materials are interpreted in the light of the known information on chemical structure. Several examples of archaeological specimens which have been characterized are included. Two large groups of modern materials, a group of plastic sculptures and a collection of early plastic objects were characterized. Areas for future work include an expanded reference collection of modern materials and 2 the use of J-CAMP-DX programming language for interlaboratory exchange of data which is independent of the brand of spectrometer used. 3 t TABLE OF CONTENTS VOLUME 1 Abstract 2 List of figures 11 List of tables 19 Acknowledgement s 23 Preface 25 Chapter 1 Literature survey on the use of infrared spectroscopy 28 in museum work Introduction 28 1953 - 1960 28 1961 - 1970 33 1971 - 1980 53 1981 - 1988 67 Conclusion 79 Chapter 2 Diffuse reflectance spectroscopy 82 FT—IR spectroscopy 82 Diffuse reflectance spectroscopy 86 Development of diffuse reflectance spectroscopy 86 Quantitative analysis 90 Qualitative analysis 98 Silicon carbide paper sampling technique 103 Other applications of diffuse reflectance spectroscopy 109 Multicomponent analysis 112 Introduction 112 Thin layer chromatography/FT-IR 112 HPLC/FT—IR 115 FT-IR microscopy 120 Chapter 3 Experimental procedure 131 Instrument specifications 131 FT-IR spectrometers 131 Diffuse reflectance accessory 133 FT-IR microscope 138 4 Experimental procedure for diffuse reflectance 139 General procedure 139 Instrument preparation 141 Background spectra collection 141 Sample spectra collection 144 Sample preparation for diffuse reflectance 145 Difficulties with the silicon carbide paper technique 147 Data handling 150 Identification of unknowns 152 Experimental procedure for thin layer chromatography samples 155 Preparation of thin layer chromatography samples 155 Interpretation of thin layer chromatography sample spectra 157 Experimental procedure for FT-IR microscopy 161 Chapter 4 Waxes 166 Beeswax 166 Source 166 Composition 166 Identification and interpretation of standard spectra 168 Identification of unknown samples 176 Unadulterated beeswax 176 Beeswax mixtures 179 Spermaceti wax 182 Source 182 Composition 183 Identification of standard spectrum 183 Carnauba wax 185 Source 185 Composition 186 Interpretation of standard spectra 187 Identification of unknown sample 189 Candelilla wax 190 Source 190 Composition 190 Identification of standard spectrum 191 Paraffin wax 192 Source 192 Composition 192 Interpretation of standard spectra 192 Identification of unknown samples 193 5 Chapter 5 Fats and oils 210 Source 210 Composition 210 Unaltered fats and oils 210 Effects of ageing 212 Identification and interpretation of standard spectra 212 Standard sample information 212 Vegetable and seed oils 213 Lamb suet 218 Fatty acids 222 Identification of unknown samples 228 Unknown sample information 239 Chapter 6 Bituminous materials 250 Bitumen 250 Source 250 Composition 254 Identification and interpretation of standard spectra 257 Identification of unknown samples 263 Shale, jet and dopplerite 264 Source 264 Composition 265 Identification and interpretation of standard spectra 265 Identification of unknown samples 271 Chapter 7 Resins and related materials 282 Resins 282 Source 282 Composition 282 Diterpenoid resins 285 Triterpenoid resins 286 Ageing 288 Interpretation of standard spectra 289 Identification of unknown samples 296 Unknown sample information 302 Resins 302 Resin mixtures 305 Amber 308 Source 308 Composition 309 Baltic amber 309 Other ambers 310 6 Interpretation of standard spectra 310 Literature values 310 Reference sample information 314 Interpretation of standard spectra 314 Identification of unknown samples 315 Unknown sample information 315 Interpetation of unknown sample spectra 315 Shellac 317 Source 317 Composition 317 Structure of fresh shellac 317 Effects of ageing 321 Identification and interpretation of standard spectra 321 Identification of unknown sample 327 Pitch and tar 330 Source 330 Composition 331 Interpretation of standard spectra 333 Identification of unknown samples 340 Unknown sample information 344 Gums and gum resins 348 Gums 348 Source 348 Composition 351 Identification and interpretation of standard 353 spectra Gum resins 359 Source 359 Composition 359 Interpretation of standard spectra 360 Identification of unknown samples 361 Chapter 8 Proteins 391 Source 391 Structure and identification 391 Interpretation of standard spectra 392 Standard sample information 392 Interpretation of standard spectra 392 Identification of unknown sample 394 7 VOLUME 2 Chapter 9 History and development of early plastics 400 Introduction 400 Polymerization 400 Natural plastics 402 Gutta percha 403 Natural rubber 404 Twentieth century 406 Cellulose nitrate 407 History 407 Chemical structure and nomenclature 411 Production method 414 Preparation of cellulose linters 414 Esterification or "nitration" of cellulose 418 Production of cellulose nitrate plastic and 423 additives Trade names and applications 429 Cellulose acetate 432 History 432 Chemical structure and nomenclature 433 Production method 434 Acetylation of cellulose 434 Compounding of cellulose acetate and additives 438 Trade names and applications 445 Casein plastic 447 History 447 Chemical structure 448 Production method 449 Isolation of casein from milk 449 Production of casein plastic and additives 451 Trade names and applications 457 Poly (methyl methacrylate) 459 History 459 Chemical structure 460 Production method 461 Synthesis of methyl methacrylate monomer 461 Polymerization 462 Processing methods for poly(methyl methacrylate) 468 additives Trade names and applications 470 8 Chapter 10 Interpretation of reference plastic spectra 478 Description of reference materials 478 Interpretation of reference spectra 480 Cellulose nitrate 480 Cellulose acetate 483 Casein 489 Poly (methyl methacylate) 495 Chapter 11 Identification of Science Museum, Vestry House Museum and 504 Tate Gallery samples Description of samples 504 Science Museum samples 504 Vestry House Museum samples 504 Tate Gallery samples 505 Gabo sculpture samples 505 Other Gabo samples 506 Interpretation of sample spectra 507 Science Museum samples 507 Vestry House Museum samples 509 Tate Gallery samples 511 Gabo sculpture samples 511 Gabo experimental plastic samples 517 Gabo surface exudate samples 526 Gabo sculpture adhesive sample 536 Chapter 12 Polymer degradation mechanisms 565 Introduction 565 Sources of energy for bond scission 567 Degradation of plastics 572 Cellulose nitrate 572 Cellulose acetate 578 Casein 589 Poly (methyl methacrylate) 590 Chapter 13 Survey of objects from the Plastics Historical 592 Society Introduction 592 Natural plastics 592 Gutta percha 593 Rubber 598 Vulcanized rubber 598 Vulcanite 602 9 Shellac 606 Bois durci (Albumen and wood flour) 608 Semi-synthetic plastics 611 Cellulose nitrate 611 Parkesine 611 Xylonite 612 Cellulose acetate 614 Casein 614 Synthetic plastics 616 Phenol formaldehyde 616 Amino plastics 620 Chapter 14 Identification of old conservation materials found on 644 objects Introduction 644 Nimrud ivories 644 Stone consolidation material from marble frieze 654 Material from glass painting 655 Coating from glass lithograph fragment 656 Paraffin wax 660 Material from Mask of Thay 661 In situ analysis of coatings on metal objects 663 Chapter 15 Conclusions 672 Appendix 676 References 687 10 LIST OF FIGURES Figure 2.1 Diagram of the Michelson interferometer (Griffiths and de Haseth, 1986). Figure 2.2 Illustration of specular and diffuse reflectance (Willey, 1976). Figure 3.1 Diagram of diffuse reflectance FT-IR system developed by Fuller and Griffiths