THE EFFECTS of SEVERAL PAPER CHARACTERISTICS and APPLICATION METHODS on the SUBLIMATION RATE of CYCLODODECANE by Kelli A. Piot

Home , Cyclododecane, Laurolactam, Nylon 12

THE EFFECTS OF SEVERAL PAPER CHARACTERISTICS AND APPLICATION METHODS ON THE SUBLIMATION RATE OF CYCLODODECANE

Kelli A. Piotrowski

A thesis submitted to the Department of Art

In conformity with the requirements for

the degree of Master of Art Conservation

Queen’s University

Kingston, Ontario, Canada

(September, 2013)

ABSTRACT

Cyclododecane (CDD) is a waxy, solid cyclic hydrocarbon (C12H24) that sublimes at room temperature and possesses strong hydrophobicity. In paper conservation CDD is used principally as a temporary fixative of water-soluble media during aqueous treatments. Hydrophobicity, ease of reversibility, low toxicity, and absence of residues are reasons often cited for its use over alternative materials although the latter two claims continue to be debated in the literature. The sublimation rate has important implications for treatment planning as well as health and safety considerations given the dearth of reliable information on its toxicity and exposure limits. This study examined how the rate of sublimation is affected by fiber type, sizing, and surface finish as well as delivery in the molten phase and as a saturated solution in low boiling petroleum ether. The effect of warming the paper prior to application was also evaluated. Sublimation was monitored using gravimetric analysis after which samples were tested for residues with gas chromatography-flame ionization detection

(GC-FID) to confirm complete sublimation. Water absorbency tests were conducted to determine whether this property is fully reestablished. Results suggested that the sublimation rate of CDD is affected minimally by all of the paper characteristics and application methods examined in this study.

The main factors influencing the rate appear to be the thickness and mass of the CDD over a given surface area as well as temperature and ventilation. The GC-FID results showed that most of the

CDD sublimed within several days of its disappearance from the paper surface regardless of the application method. Minimal changes occurred in the water absorbency of the samples following complete sublimation.

ACKNOWLEDGEMENTS

I would like to express my tremendous gratitude to my advisers Dr. Alison Murray and John

O’Neill for their advice, guidance, and encouragement throughout my research. I would also like to thank Rosaleen Hill for her suggestions at various stages of my work. I am grateful to Dr. George

Bevan of the Department of Classics, Dr. P. James McLelland of the Department of Chemical

Engineering, and Dr. Bubby Kettlewell of the Analytical Services Unit for sharing their insights on statistical modeling and analysis. I am also indebted to Dr. Season Tse of the Canadian Conservation

Institute for her generous comments and suggestions. I would like to extend my thanks to Dr.

Allison Rutter and Paula Whitley of the Analytical Services Unit at Queen’s University and Dr. H. F.

(Gus) Shurvell of the Art Conservation Program for their assistance in the technical analyses. Finally,

I would like to thank my friends, family, and colleagues for their encouragement and support.

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TABLE OF CONTENTS

Title page..……………………………………………………….…………………………………i

Abstract...………..…………………………………………………………………………………ii

Acknowledgements.……………..…………………………………………………………………iii

Table of Contents..………………………………………………………………………………...iv

List of Tables..……..………………………………………………………………………………vi

List of Figures..……………………………………………………………………………………vii

Chapter 1 Introduction...... ……………………………………………………………....………….1

Chapter 2 Literature Review………………………………………………………………………..3

2.1 Uses in Paper Conservation…………………………………………………………….3

2.2 Physical Properties……………………………………………………………………...8

2.3 Uses in Industry…………………………………………………………………….....10

2.4 Health and Safety……………………………………………………………………...11

2.5 Methods of Application……………………………………………………………….12

2.6 Factors that Affect Sublimation……………………………………………………….15

2.7 The Potential Presence of Residues……………………………………………....……18

Chapter 3 Experimental……………………………………………………………….…………..20

3.1 Evaluation of Cyclododecane Purity……………………………………….…………..21

3.2 Gravimetric Procedures to Determine CDD Sublimation Rates……………………….28

Experiment 1: Fiber Type…………………………………………...... ……..28

Experiment 2: Sized and Waterleaf Papers…………………………………...……31

Experiment 3: Finishes……………………………………………………………32

Experiment 4: Warmed and Unwarmed Substrates………………………………..33

Experiment 5: Molten CDD and CDD-Saturated Solution………………………..35

3.3 GC-FID Procedures to Test for the Presence of Residues…………………………….38

3.4 Water Absorbency Tests………………………………………………………………39

Chapter 4 Results and Discussion…………………………………………………………………44

4.1 Gravimetric Analyses………………………………………………………………….44

4.2 Gas Chromatography-Flame Ionization Detection Analyses…………………………..58

4.3 Water-Absorbency Analyses…………………………………………………………...61

Chapter 5 Conclusions………………………………………………………….…………………68

Bibliography………………………………………………………………………………………71

Appendices

Appendix 1: Materials and Suppliers………………………………………………………76

Appendix 2: Summary of Temperature and Relative Humidity during Gravimetric Tests…………………………………………………………………………77

Appendix 3: Dependence of Paper Mass on RH: Graphs of Controls…………………….78

Appendix 4: Calibration Curves and GC-FID Results for CDD Purity Characterization.…83

Appendix 5: GC-FID Results for Warmed and Unwarmed Whatman Filter Paper Samples Treated with Molten Cyclododecane…………………………………………..…84

Appendix 6: GC-FID Results for Waterleaf and Gelatin-Sized Flax Paper Samples Treated with Molten Cyclododecane…………………………………………..…86

Appendix 7: GC-FID Results for Artistico Rough Paper Samples Treated with Molten Cyclododecane and CDD-Saturated Solutions………………………………….…88

LIST OF TABLES

Table 1: Physical Properties of Cyclododecane………………………………………………..……9

Table 2: Average Initial Mass and Thickness of Cotton, Flax, Kozo, and Groundwood Fiber Paper Samples and Cyclododecane Applied as a Melt…………………….…..29

Table 3: Average Initial Mass and Thickness of Waterleaf and Gelatin-Sized Flax Paper Samples and Cyclododecane Applied as a Melt……………………………………………..32

Table 4: Average Initial Mass and Thickness of Cold Pressed, Hot Pressed, and Rough Paper Samples and Cyclododecane Applied as a Melt……………………………………...33

Table 5: Average Initial Mass and Thickness of Whatman Filter Paper Samples and Cyclododecane Applied as a Melt Onto Unwarmed and Warmed Substrates…………………...…34

Table 6: Average Initial Mass and Thickness of Whatman Filter Paper Samples and CDD Applied as a Melt and a Saturated Solution in Petroleum Ether (30°C-40°C)……….………37

Table 7: Average Percent Mass Loss of CDD from Cotton, Flax, Kozo, and Groundwood Papers Over Time………………………………………………………………….47

Table 8: Average Percent Mass Loss of CDD from Waterleaf and Gelatin-Sized Flax Papers Over Time……………………………………………………………………………50

Table 9: Average Percent Mass Loss of CDD Over Time from Cold Pressed, Hot Pressed, and Rough Finish Fabriano Artistico Papers………………………………………………………52

Table 10: Average Percent Mass Loss of CDD Over Time from Whatman Filter Paper Treated With Molten CDD to Unwarmed and Warmed Substrates……………………………….55

Table 11: Average Percent Mass Loss of CDD, Applied as a Melt and as a Saturated Solution in Petroleum Ether (30°C-40°C), from Fabriano Artistico Rough Finish Paper……….…57

Table 12: GC-FID Results of Select CDD-Treated Paper Samples Post-Sublimation……………..60

Table 13: Water Absorbency of Whatman Filter Paper Control and Warmed and Unwarmed Samples Post-Sublimation of Molten Cyclododecane……………………………………………...62

Table 14: Post-Sublimation Water Absorbency of Waterleaf and Gelatin-Sized Flax Paper Treated with Molten Cyclododecane………………………………………………………..64

Table 15: Post-Sublimation Water Absorbency of Fabriano Artistico Rough Finish Paper Treated with Molten CDD and CDD-Saturated Solution in Petroleum Ether (30ºC -40ºC) and Controls…………………………………………………………...……………………….…67

LIST OF FIGURES

Figure 1: Molecular structures of cyclododecane…………………………………………………..10

Figure 2: Tools for applying cyclododecane……………………………………………...………..15

Figure 3: FTIR spectrum of cyclododecane………………………………………………….……23

Figure 4: Detail of GC-FID chromatogram of cyclododecane………………………………..…....25

Figure 5: GC-MS chromatogram of cyclododecane………………………………….………..…...27

Figure 6: Modified electric kistka…………………………………………………………….….....30

Figure 7: Arrangement of samples and controls in fume hood……………...……….………….…31 . Figure 8: Warming of paper samples……………………………………………………………....35

Figure 9: Detail of paper samples with templates and slide warmer……………..…………...….…35

Figure 10: Molten CDD applied to unwarmed Whatman filter paper #1…………….……....…….35

Figure 11: Molten CDD applied to warmed Whatman filter paper #1…………………………….35

Figure 12: Device for applying the CDD-saturated solution………………………………….…....38

Figure 13: Suspension of samples prepared with molten CDD and CDD-saturated solution..….…38

Figure 14: Preconditioning chamber……………………………………………………………....41

Figure 15: Mean sublimation rates of CDD, applied as a melt, from unsized cotton, flax, kozo, and groundwood papers plotted as a function of total mass loss against time………….46

Figure 16: Mean sublimation rates of CDD from cotton, flax, kozo, and groundwood papers plotted as a function of total mass against time with error bars showing standard deviations for 20 measurements…………………………………………………………………...47

Figure 17: Mean sublimation rates of CDD, applied as a melt, from waterleaf and gelatin-sized flax papers plotted as a function of total mass loss against time……………...………49

Figure 18: Mean sublimation rates of CDD from waterleaf and gelatin-sized flax papers plotted as a function of total mass against time with error bars showing standard deviations for 20 measurements…………………………………………………………….……..49

Figure 19: Mean sublimation rates of CDD, applied as a melt, from cold pressed, hot pressed, and rough finish Fabriano Artistico papers plotted as a function of total mass loss against time…..51

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Figure 20: Mean sublimation rates of CDD, applied as a melt, from cold pressed, hot pressed, and rough finish Fabriano Artistico papers plotted as a function of total mass against time with error bars showing standard deviations for 20 measurements…………………………….…..52

Figure 21: Mean sublimation rates of CDD, applied as a melt to warmed and unwarmed Whatman filter paper samples, plotted as a function of total mass loss against time……………….54

Figure 22: Mean sublimation rates of CDD, applied as a melt to warmed and unwarmed Whatman filter paper samples, plotted as a function of total mass against time with error bars showing standard deviations for 20 measurements…………………………………………...54

Figure 23: Mean sublimation rates of CDD, applied as a melt and as a saturated solution in petroleum ether (30°C-40°C), from Fabriano Artistico rough finish paper with data plotted as a function of total mass loss against time…………………………………………………………....56

Figure 24: Mean sublimation rates of CDD, applied as a melt and as a saturated solution in petroleum ether (30°C-40°C), from Fabriano Artistico rough finish paper with data plotted as a function of total mass against time and error bars showing standard deviations for 20 measurements……………………………………………………………………………...57

Figure 25: Boxplot of time required for 0.05 mL of water to be absorbed by Whatman filter paper controls and samples post-sublimation of molten CDD from warmed and unwarmed substrates……………………………………………………………………………...63

Figure 26: Boxplot of time required for 0.1 mL of water to be absorbed by waterleaf flax paper controls and samples post-sublimation of molten CDD…………………………………….65

Figure 27: Boxplot of water mass absorbed in two minutes by gelatin-sized controls and samples post-sublimation of molten CDD……………………………………...…………………65

Figure 28: Boxplot of water mass absorbed in two minutes by Fabriano Artistico rough controls and samples post-sublimation of molten CDD and CDD-saturated solution in petroleum ether (30ºC-40ºC)…………………………...………………………………………….67

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CHAPTER 1

INTRODUCTION

Since the late 1990s most paper conservation studies on cyclododecane (CDD) have focused on developing techniques for achieving maximum hydrophobicity. To this end, researchers have compared the efficacy of various application methods while also identifying inherent factors in the paper and media that could influence treatment outcomes. These valuable case studies and experiments have provided paper conservators with practical guidelines for using CDD on a range of common media and paper types. They have also articulated its advantages over alternative materials and identified some of its limitations. Consequently, today CDD is an established conservation material used by paper conservators for the protection of vulnerable media and embossings during aqueous treatments.

Despite nearly fifteen years of use in the field of paper conservation, rigorous analytical studies on CDD and its interaction with paper are still wanting. The vast majority of analytical research conducted on CDD has been performed in the service of objects conservation. Some of this research is applicable to paper conservation such as the study by Caspi and Kaplan (2001), which revealed the range of potential impurities that can be found in CDD; however, a closer examination of its interactions with paper would seem to be warranted given its indeterminate rate of sublimation from paper and the persistent question of residues. This study sought to discover how several inherent paper characteristics and CDD application techniques affect the rate of sublimation by using a combination of gravimetric analysis, gas chromatography-flame ionization detection, and water absorbency tests. The impact of four fiber types was evaluated as well as the presence of sizing and the surface texture of paper. The effects of the following application methods were also explored: delivery in the molten phase and as a saturated solution in low boiling solvent and the application of molten CDD onto pre-warmed substrates. It was hoped that the results of

this study could provide conservators with sufficient information for treatment planning and a measure of certainty regarding the point of complete sublimation.

CHAPTER 2

LITERATURE REVIEW

2.1 USES IN PAPER CONSERVATION

Cyclododecane (CDD) is a white, waxy, alicyclic hydrocarbon (C12H24) that sublimes at room temperature and easily dissolves in a variety of nonpolar solvents. Its use as a conservation material dates to 1995 when Hans Michael Hangleiter, Elisabeth Jägers, and Erhard Jägers explored its potential, along with that of several volatile monoterpenoids, in a quest to find an easily reversible, hydrophobic consolidant of low or no toxicity. Soon thereafter Hangleiter (1998) published two case studies on the treatment of fifteenth-century murals in which he reported successful results using

CDD as a temporary consolidant and barrier during surface cleaning and removal of water-soluble adhesives. CDD has since been used in numerous treatment applications on objects of diverse composition. Its ability to sublime at room temperature and standard atmospheric pressure has made it an attractive alternative to materials requiring removal by physical or chemical interventions.

Cyclododecane has been used to temporarily secure unstable surfaces on ceramic vessels

(Caspi and Kaplan 2001; Cleere 2005), polychrome sculptures (Hiby 1999), and wall paintings

(Singleton et al. 2006) prior to transportation. It has been tested as a self-releasing barrier film for molding and casting of fossil specimens (Arenstein et al. 2004), terracotta shards (Brückle et al.

1999), marble sculpture (Maish and Risser 2002), and stone ornaments (Mas i Barberà et al. 2008).

CDD has also been used as a hydrophobic barrier to protect water-soluble dyes on textiles (Hiby

1997) and an unbaked mud statue during water-soluble adhesive removal (Rozeik 2009).

In the field of paper conservation CDD has been predominantly used to protect water- sensitive media during aqueous treatments (Bandow 1999; Blüher et al. 1999; Brückle et al. 1999;

Chevalier 2001; Keynan and Eyb-Green 2000; Jonynaité et al. 2008; Kozub 2009; Muñoz-Viñas

2007; Scharff and Nielsen 2003). Alternatively, it has been employed as a temporary fill material to

maintain the contours of sharply defined embossings during aqueous immersion (Hendry 2001). The literature does not record its use as a protective mask for alkaline-sensitive media during deacidification although its film-forming characteristics suggest this application as well. Its potential use as a dam to confine water-infused poultices has also been proposed (Keynan and Eyb-Green

2000).

Analogous to the ways in which paper conservators use alternative fixatives, CDD is applied locally to relatively small features of an object such as stamps, signatures, inscriptions, or discrete areas of color. There are several disincentives to masking larger areas with CDD besides its time- consuming application. CDD necessarily coats the fibers as well as the media thereby protecting the latter while inhibiting the beneficial effects of washing to the former. The treated and untreated areas of the object may therefore assume a dissimilar appearance especially in cases where washing is accompanied by bleaching. Areas fixed with CDD may also be more prone to cockling, tensions, and edge discoloration (Bandow 1999; Blüher et al. 1999; Muñoz-Viñas 2007).

Paper conservators first began to explore the use of CDD as a hydrophobic barrier in the late 1990s. Agnes Blüher et al. (1999) compared its efficacy in the molten form against three temporary nonvolatile fixatives (gelatin, paraffin, and Paraloid B-72) and two permanent ionic fixatives (Rewin EL and Mesitol NBS) for the protection of aniline-based media. Following a series of aqueous immersion tests, CDD was judged to be the most useful of the temporary fixatives based on its performance in relation to gelatin and its uncomplicated removal in comparison to paraffin and Paraloid B-72. The labor-intensive local application of CDD was considered a disadvantage for mass treatments in contrast to ionic fixatives, which can be applied by bath immersion if all media on a given document are uniformly charged. Cyclododecane, on the other hand, caused no perceptible discoloration of the paper nor did it attract water-soluble degradation products as had

Mesitol NBS and Rewin EL, respectively. In summary CDD was considered to be the most suitable fixative whenever media cannot be permanently fixed.

A concurrent study undertaken by Brückle et al. (1999) tested the ability of molten CDD to protect two types of water-soluble media — a red modern ink stamp and historic iron gall ink — while also examining the influence of inherent paper characteristics on treatment outcomes. The modern ink was applied to nineteenth century alum-rosin sized and waterleaf rag papers and fixed with either molten CDD or a 15% solution of Paraloid B-72 in 1:1 xylene/toluene. The samples were then subjected to a series of aqueous treatments of varying lengths ranging from five to sixty minutes in baths of deionized and alkalized water. Comparably minimal ink movement was observed during humidification and blotter washing irrespective of the paper type, duration, or fixative; however, during float washing and immersion less movement occurred with inks treated with CDD.

Molten CDD was also tested on historic iron gall inks inscribed on (1) thin gelatin-sized handmade rag paper; (2) smooth, alum-sized machine made bast fiber paper; and (3) a thick, moderately textured alum-sized machine made paper of unspecified fiber content. All samples were float washed although the duration varied by the requirements of the objects. Only the ink on the thinnest paper was unsuccessfully protected.

In conclusion, Brückle et al. found that CDD was most suited for protecting moderately water-sensitive media. It performed best on papers that expand minimally with the introduction of moisture. This may be due to the development of cracks in the film as a result of differential expansion or by undulations in the paper at the film edge. The authors also observed that short- fibered papers are less likely to draw water into the fixed areas thereby reducing the occurrence of lateral bleeding. To improve penetration, a dual-sided application and slight warming of the substrate was suggested. These two recommendations were incorporated into the experiments undertaken by Bandow (1999), Chevalier (2001), and Scharff and Nielsen (2003).

Chevalier (2001) also examined the efficacy of CDD as a hydrophobic barrier, but on a more diverse sample population. The CDD was delivered in the molten form and as a saturated solution in n-heptane. Media included porous point pen, ballpoint pen, and watercolor as well as office stamps and iron gall ink. The papers encompassed sized and unsized, handmade and machine made papers composed of rag, cotton, and wood pulp. Samples underwent accelerated aging following media application. In many cases the molten CDD and the CDD-saturated solution provided comparable protection with several notable exceptions. Molten CDD was more effective at protecting the black office stamp and the red porous pointed pen irrespective of paper type with one exception: the red ink on unsized filter paper showed less movement when treated with the CDD- saturated solution. Presumably this is because the ink was distributed well below the paper surface and only the solvent-delivered CDD could migrate deeply into the paper. Interestingly, the author reported superior results of CDD in solution on iron gall ink on handmade paper, bond paper, and newsprint. On all other substrates the efficacy of the melt and solution was identical. It is unclear whether heat, coverage, or other factors influenced these outcomes. For future study, a dual method of application was suggested in which the first layer of CDD is applied to a lightly heated substrate to encourage penetration followed by a second coating. The author discouraged the use of heated spatulas to promote diffusion as the heat accelerates sublimation thus reducing coverage.

Keynan and Eyb-Green (2000) tested CDD on modern media and artists’ papers that contain a variety of fillers, optical brighteners, and sizings. The CDD was applied in the molten state and as saturated solutions in isooctane and n-heptane. Slow evaporating solvents were chosen to increase the penetration of the CDD. The authors acknowledged that larger crystals would form, but would create more uniform films. Jägers and Jägers (1999) had earlier recommended the use of low boiling solvents (b.p. range 30˚C-40˚C) to achieve comparable hydrophobicity to the melt. Samples were humidified before applying the CDD in order to minimize stresses at the wet-dry interface and

to replicate common treatment practice. To improve penetration, pure solvent was introduced to the sample before applying the saturated solution. A heated spatula was used to drive the molten CDD further into the paper. No tidelines or alterations to the surface texture were observed under natural light; however, several papers exhibited tidelines under ultraviolet radiation. The authors speculated that water-soluble components in the paper may have become mobile and deposited along the film edge. A second experiment examined the effectiveness of molten CDD on modern inks, color pencils, and copy pencil applied to the same variety of artists’ papers and subjected to thirty minutes of float washing. The authors found that CDD protected the media only if applied to both sides. In summary, the substrate appeared to be the determining factor in the success of the treatment although the authors were unable to identify which paper characteristics played the most important role. The media’s sensitivity to heat must also be considered when using the melt. Keynan and Eyb-

Green observed that the films sublimed within several days, but did not provide any further information.

Scharff and Nielsen (2003) tested several methods of CDD application on highly water- soluble Remazol dye inscribed on unsized Whatman filter paper. Single- and double-sided applications of molten CDD were applied to samples at room temperature and at 43°C. A heated spatula was then used to drive the CDD further into the paper on selected samples of the population. To determine the relative effectiveness of the treatments, cold water was introduced to the samples in three ways: (1) as single drops to both sides of the substrate, (2) as several drops on a suction table, and (3) in a ten-minute bath immersion. The best results were obtained when the molten CDD was applied to both sides of a uniformly heated substrate. The authors also tested a

CDD-saturated solution in high boiling petroleum ether on unheated samples half of which were pretreated with the pure solvent prior to dispensing the solution. Each of the two sample sets received both single- and double-sided applications. None of the samples were successfully

protected using this method. These findings comport with the recommendations of Jägers and

Jägers (1999) who stressed the use of low-boiling solvents to achieve comparable effectiveness with molten CDD.

Bandow (1999) also investigated using molten and solvent-delivered cyclododecane as a hydrophobic barrier over water-sensitive colored inks on typing paper, photocopy paper, mechanical wood pulp and rag papers, coated ledger paper, and art paper. Effective barriers were formed on thick, absorbent papers, but less success was achieved on hard-sized papers due to insufficient penetration. The author made several observations concerning sublimation presumably by visual examination as no analytical methods were noted. Delivered as a saturated solution, CDD sublimed between 24 and 48 hours. Delivered as a melt, CDD sublimed within eight to ten days depending on the thickness of the film and whether a dual-sided application was employed. Occasionally small, white residues remained which could be removed mechanically.

2.2 PHYSICAL PROPERTIES

Cyclododecane (C12H24) (CAS 294-62-2) (EINECS 206-033-9) is an alicyclic saturated hydrocarbon with a molecular weight of 168.31 g/mol. It is a white, wax-like solid at room temperature with a melting point in the range of 59ºC to 61ºC. It is readily soluble in nonpolar solvents such as aliphatic and aromatic hydrocarbons and nearly insoluble in polar solvents such as water, alcohols, and ketones. It is slightly soluble in esters, ethers, and halogenated hydrocarbons

(Jägers and Jägers 1999). Many of the quoted values for its boiling point, flash point, ignition temperature, and vapor pressure vary significantly on the source. Rowe and Rozeik (2008) discovered a pronounced inconsistency in the values reported in the Material Safety Data Sheets

(MSDS) issued by several manufacturers and distributors. As seen in table 1, a similar inconsistency was found in the physical data provided by a somewhat different group of manufacturers, suppliers, government agencies, and standard chemical references.

TABLE 1: PHYSICAL PROPERTIES OF CYCLODODECANEA

Melting Boiling Flash Ignition Vapor Specific Density Solubility Point Point Point Temperature Pressure Gravity (g/mL) in Water (ºC) (ºC) (ºC) (ºC) European Chemical 98 ~0.1 0.83 0.01 g/L Bureaub 61 243 (closed — hPa at — g/cm3 at at 20ºC Data Set cup) 20ºC 65ºC

Handbook of Environmental 0.1 hPa Data on Organic 61 243 — — — — — at 20ºC Chemicalsc

>93 10 mm INVISTA 0.82 at 60.7 247 (closed — Hg at — — Data Sheet 80ºC cup) 100ºC Kremer Pigments 1.33 kPa 0.01 g/L 60.7 247 98 175 — — MSDS at 100ºC at 20ºC

Patty’s 0.863 at Toxicologyd 61 239 — — — — — 20ºC

89 Sigma Aldrich 59 — (closed — — — — — MSDS cup) a References in Bibliography b European Commission, European Chemical Bureau, International Uniform Chemical Information Database c In Bibliography, see Lide and Milne d. In Bibliography, see Baxter

The molecular structure of cyclododecane is typically illustrated as in fig. 1a although this is a highly simplified description that does not reflect its three-dimensionality. CDD is known to assume several conformations although it preferentially adopts a single conformation in the solid state regardless of crystal packing (figs. 1b and 1c) (Atavin 1989; Khorasani et al. 2012). The property that distinguishes cyclododecane from most other barrier films used in conservation is its ability to sublime at room temperature and standard atmospheric pressure; a trait linked to its high vapor pressure (0.1 hPa at 20º) and low enthalpy of sublimation (ΔH = 76.2 kJ/mol-1 at 25ºC) (Chickos

and Acree 2002). Although camphene and menthol, two other molecules examined by Hangleiter,

Jägers, and Jägers also have the capacity to sublime at room temperature, their use has not been widely adopted. Undoubtedly this is due to their reactive function groups, which limit their applicability.

Fig. 1: Molecular structures of cyclododecane

Molecular structure of CDD Major conformation of CDD Minor conformation of CDD

Fig. 1a Fig. 1b Fig. 1c Figures 1b and 1c reproduced from Atavin et al 1989.

2.3 USES IN INDUSTRY

The synthesis of cyclododecane is traced to the early macrocyclic research of Nobel Laureate

Leopold Ruzicka in Switzerland during the mid-1920s (Bürgi 1993; Prelog and Jeger 1980). His research on the molecular structure of muscone and civetone, two animal-based fragrances comprised of sixteen- and seventeen-carbon rings, respectively, disproved the dominant theory that ring strain would destabilize large cyclic molecules (Story 1972). In demonstrating the existence of such molecules in nature, Ruzicka proceeded to synthesize other macrocycles such as CDD for application in the perfume industry.

Today, cyclododecane is an intermediate in the manufacture of cyclododecanol and cyclodecanone, which are used in the synthesis of aroma chemicals and the manufacture of laurolactam, the starting material for the polyamide Nylon 12 (INVISTA 2012). CDD has comparatively fewer applications as an end product. In addition to its use as a conservation material,

CDD is used as a pore-forming agent in ceramics, as a mothproofing agent, as an emulsifier in

pesticides, and for sintering metal powders (INVISTA 2012; Patty’s Toxicology, 2012). CDD is produced by hydrogenation of 1,5,9-cyclododecatriene with nickel as a catalyst (Ullrich 2003).

2.4 HEALTH AND SAFETY

Much of the conservation literature on CDD cursorily addresses issues of health and safety.

The majority of studies simply note that CDD is non-toxic or of low-toxicity and cite several early articles by Hangleiter, Jägers, and Jägers as supporting documentation. Few studies have looked outside the conservation literature for information on its potential impact on human health and the environment. Notable exceptions are review articles by Pool (2006) and Rowe and Rozeik (2008), which made ample use of the occupational health and safety literature to highlight the ambiguity surrounding CDD’s safety and the need for further research. Governmental agencies charged with assessing chemical safety, such as the United States’ National Institute for Occupational Health and

Safety (NIOSH) and the Occupational Health and Safety Administration (OSHA) have been slow to produce such studies and have still not set permissible exposure limits. This may be due to the way that CDD is used in industry i.e., as an intermediate in an enclosed system, which reduces exposure to the worker. Assessments of CDD’s safety should also reflect how it is used by conservators, but so far such research is lacking.

To date, there are no studies on the long-term human health effects of CDD and there are few studies on its short-term effects. The principal routes of entry are respiratory and dermal.

Anecdotal evidence points to respiratory difficulties, headaches, and irritation of the eyes shortly after exposure to its vapors (Vernez et al 2011). There is also some indication that CDD is bioaccumulative. Its presence was detected in the expired air of 62 nonsmoking human subjects in a study investigating the bioaccumulation of environmental pollutants (Krotoszynski et al. 1982) and has also been found in aquatic species (Passino and Smith 1987). It is unclear what effect the bioaccumulation of CDD may have on human health. Rowe and Rozeik (2008) noted that CDD

met the European Chemicals Bureau criteria as a PBT (persistent, bioaccumulative, toxic) or vPBT

(very persistent, bioaccumulative, toxic) chemical although further research was not recommended since CDD is used primarily as an intermediate.

In the absence of permissible exposure limits, the use of personal protective equipment is highly recommended including nitrile rubber gloves and safety glasses with protective shields

(Kremer 2010). To prevent inhalation of potentially harmful vapors, CDD should be used in a fume hood. A recent study examining exposure levels of CDD during typical conservation practices showed that the concentration of CDD vapors in a fume hood was reduced from 15.5 mg/m3 to

0.85 mg/m3 simply by standard airflow (Vernez et al. 2011). Moreover, conservators have been cautioned to keep CDD-treated objects in a fume hood with the ventilation on until some time after the CDD is no longer visible (Pool 2006).

2.5 METHODS OF APPLICATION

In conservation practice, CDD is delivered as a molten liquid, a saturated solution, or an aerosol spray. Each method of application produces heterogeneous films consisting of a network of crystals, which are distinguished by their size, shape, and density. These qualities impact both the water-repellency of the films and their rate of sublimation. Molten CDD produces the densest films with the smallest crystals, but also require the most time to sublime (Bandow 1999; Cleere 2005;

Hiby 1997; Muros and Hirx 2004; Riedl and Hilbert 1998). When the goal of the treatment is to create a hydrophobic barrier, the molten form is almost always preferred (Brückle et al. 1999;

Chevalier 2001; Keynan and Eyb-Green 2000; Muñoz-Viñas 2007; Muros and Hirx 2004).

Applied as a saturated solution, CDD forms thin films of large needle-like crystals. The size and compactness of the crystals is influenced by the rate of solvent evaporation with more volatile solvents producing smaller, more densely packed crystals (Stein et al. 2000). Although the porosity of these films reduces its effectiveness as a hydrophobic barrier, conservators can control the density

of the film by their choice of solvent. Many previous studies examining the efficacy of the melt in relation to the solution have used high-boiling solvents with results invariably favoring the melt

(Chevalier 2001; Keynan and Eyb-Green 2000; Scharff and Nielsen 2003). Only CDD-solutions prepared in low-boiling, highly volatile solvents, however, are capable of forming films of comparable hydrophobicity to the melt (Jägers and Jägers 1999). It is therefore not surprising that so many studies found the saturated solution to be less effective.

In virtually all of the paper conservation studies on CDD, the aerosol spray has been omitted. Information on its crystal formation can be gleaned, however, from objects conservation research. For example, Muros and Hirx (2004) tested its use for protecting water-sensitive media on ceramics. Applied to glass, they found that the spray produces small, round loosely packed crystals of an intermediate size and density to those produced by the melt and the solution. When the authors applied the spray to unglazed terracotta, the CDD failed to penetrate the surface. Like all temporary fixatives, CDD must fully envelope the media in order to be an effective hydrophobic barrier; in this particular study it failed to provide adequate results. The greater porosity of paper might facilitate greater penetration, but it would seem that much greater precision is achievable with the melt and solution. Of the three methods of application, the spray sublimes the fastest irrespective of the porosity of the substrate (Muros and Hirx 2004). This is likely due to the thinness of the film and superficial penetration.

Molten CDD solidifies rapidly at room temperature, which makes uniform application difficult and limits the penetration into porous substrates. Consequently, conservators have developed several strategies to extend the working time and to encourage greater penetration into porous substrates. Hangleiter (1998) suggests reducing the melting point by the addition of high- boiling solvents such as petroleum ether (b.p. 100°C-140°C). Other conservators have recommended warming the substrate (Arenstein 2004; Brückle et al. 1999; Scharff and Nielsen 2003;

Stein et al. 2000). Scharff and Nielsen (2003) found that the most effective hydrophobic barrier films were obtained when molten CDD was applied to paper warmed to ~40°C. Any modification that retards solidification, however, results in larger crystals and a correspondingly less cohesive film

(Hangleiter 2000). It would appear that delaying solidification results in a greater depth of penetration at the cost of reduced density.

Several studies indicate that molten cyclododecane is effective only if applied to both the recto and the verso (Muñoz-Viñas 2007; Scharff and Nielsen 2003). The literature does not describe the use of a suction table or disc to improve the penetration of solvent-delivered CDD into the media and fibers analogous to the application of paraffin wax in solution.

A variety of heat-producing and heat-retaining implements have also been tested such as metal droppers, thermal syringe jackets, tjanting tools, and batik balls (Arenstein et al. 2003) (fig. 2).

The latter can be fitted onto the body of a heated spatula with a thermostat control unit (Arenstein et al. 2004). Standard heated spatulas have also been used (Chevalier 2001; Hiby 1997) as well as an electric kistka, a tool for applying wax resists to traditional Ukrainian Easter eggs (Brückle et al.

1999; Chevalier 2001). Maish and Risser (2002) used a heat gun to dispense molten CDD, but found it impractical for applying uniform films over large surface areas.

Fig. 2: Tools for Applying Cyclododecane. Photo courtesy of the Conservation Staff at the National Museum of the American Indian, Smithsonian Institution

More recently, a dual layer method of application has been developed in which Paraloid B-72 is brushed over a base layer of CDD applied in the molten state (Muñoz-Viñas 2007). This technique addresses the problem of water permeating through the cracks in the CDD film. These minute fissures can form during solidification of the CDD and are exacerbated during aqueous treatments due to the differential expansion of the film and support. The more flexible, but less reversible

Paraloid B-72 acts as a sealant without seeping through the cracks and onto the support. The

Paraloid B-72 solution is prepared in acetone in order to minimize the possibility of dissolving the

CDD. The layer of Paraloid B-72 is released when the CDD sublimes.

2.6 FACTORS THAT AFFECT SUBLIMATION

The rate at which CDD sublimes from a given substrate is influenced by numerous factors including the thickness and density of the film layer, substrate porosity, depth of penetration, ambient temperature, and rate of air circulation. Some of these factors are well understood while

others remain ambiguous. Warming the substrate or increasing ventilation is known to promote sublimation while the opposite effect is achieved by limiting airflow (Jägers and Jägers 1999). Stein et al. (2000) showed that sublimation could be delayed for months if the treated object is stored in a sealed container. Reducing the temperature will also retard sublimation although this technique appears to be used infrequently.

According to Hangleiter et al. (1995), a 0.03 mm thick film of CDD applied in the molten state sublimes within 24-hours under ‘normal conditions’. Brückle et al. (1999) observed complete sublimation of a 0.08 mm thick film on glass within 72 hours at 20ºC. The sublimation time was reduced by a third when the temperature was raised to 38ºC. Arenstein et al. (2004) stated that a 1 mm thick layer of CDD on a non-porous surface will sublime in ~30 days. Given the number of variables that affect sublimation these figures can only be considered as estimates.

The delivery method also affects the rate of sublimation. The majority of studies report faster sublimation rates when CDD is delivered in solution (Bandow 1999; Cleere 2005; Hiby 1997).

Hiby (1997) measured the sublimation of CDD from glass and reported rates of 0.693 versus 1.978 g ⋅ m-2 ⋅ h-1 for the molten and the solvent-delivered CDD, respectively. Bandow (1999) and Cleere

(2005) also reported longer periods of sublimation for molten CDD applied to paper and ceramic.

Stein et al. (2000) observed faster sublimation rates from two types of porous stones when high- boiling solvent solutions were used, but that low-boiling solvent solutions and the melt were comparable. Overall, more porous stones required more time for the CDD to sublime. The authors concluded that porosity and pore size among other inherent qualities of the material influence sublimation. Arenstein et al. (2004), on the other hand, observed equivalent sublimation rates when

CDD was applied as a melt and as saturated solutions in mineral spirits and naphtha to a variety of bulking materials including cellulose powder, cellulose pulp, Japanese tissue, and sand. Although film thickness may be the determining factor in many cases, it would appear from Hiby’s observations

that molten CDD requires more time to sublime from non-porous surfaces. Confer (2006) observed that CDD sublimation was affected by the morphology of textile fibers.

Other than visual examination, the most frequently used method of monitoring sublimation from porous and non-porous substrates is gravimetric analysis, which has been used to track the movement of CDD from sandstone and limestone (Stein et al. 2000), terracotta (Muros and Hirx

2004), marble (Maish and Hirx 2002), and natural textile fibers (Confer 2006). Gravimetric analysis has also been used to understand how the addition of bulking agents such as cotton wool, Japanese papers, and cellulose powder may influence the rate of sublimation (Arenstein et al. 2004). To confirm complete sublimation from the substrates, gas chromatography-mass spectrometry (GC-

MS) has been employed (Stein et al. 2002) as well as gas chromatography-flame ionization detection

(GC-FID)(Confer 2006).

Examining the sublimation of CDD from marble Anselmi et al. (2011) utilized a combination of Fourier transform infrared reflectance (FTIR) spectroscopy, nuclear magnetic resonance (NMR) profilometry, and optical microscopy (OM). The authors stressed the importance of non-invasive analytical techniques to prevent external factors from affecting the sublimation rate.

A portable FTIR JASCO VIR 9500 spectrophotometer operating in the mid-infrared region was used to track the initial solvent evaporation and then the sublimation of the CDD films over twenty- five days. The JASCO instrument is equipped with a fiber optic probe capable of collecting spectral data at several millimeters from the sample surface. The progress of sublimation was monitored in the near infrared at 5680 and 6810 cm-1 corresponding to the C-H overtone bands. The rate of sublimation was calculated by plotting the peak areas versus time. Peak values were compiled from an average of four measurements taken over a 20-mm2 surface area. The authors also monitored the rate of sublimation as a function of film thickness over time using a Profile NMR-MOUSE®

(MObile Universal Surface Explorer). The NMR-MOUSE is a portable scanner designed for non-

destructive in situ analyses of surfaces. The 1H NMR sensor utilizes a single-sided magnetic arrangement to produce high-resolution sample profiles of 5 µm or better. The size of the sample area approximated that used in the FTIR analysis. Topographical images of the film sublimation were captured using polarized visible light microscopy.

The sublimation of cyclododecane from glass has also been captured visually using digital time-lapse photomicrography over a four-hour period (Maish and Hirx 2002). Riedl and Hilbert

(1998) were the first to use cryogenic scanning electron microscopy (cryo-SEM) to observe the sublimation of molten- and solvent-delivered CDD from pre-warmed plaster samples. The results of their study led them to caution conservators against warming porous substrates in order to avoid excessively long sublimation times. Cryo-SEM was subsequently used by Mas i Barberà et al. (2008) to capture the crystalline structure of CDD within porous stone.

2.7 THE POTENTIAL PRESENCE OF RESIDUES

Most of the conservation literature states that cyclododecane sublimes completely based on the absence of visually detectable residues; however, few studies have employed instrumental methods of analysis to investigate this claim. The prevailing assumption is that any residues remaining in or on the substrate are due to the presence of non-volatile impurities (Horie 2010).

Several authors have recommended that only pure CDD should be used in the conservation of cultural heritage objects (Hiby 1997; Jägers and Jägers 1999). As many conservation labs do not have access to the highly sensitive instruments necessary to conclusively make this determination,

Arenstein et al. (2004) suggested testing each new batch of CDD by applying a small amount onto a glass slide and examining the surface for residues following sublimation. In this same study, the authors observed a “small residual smudge”, but no attempt at identification was made. Maish and

Risser (2002) conducted a similar test using solvent-delivered CDD on glass and found that a “faint

‘tidal’ film” remained, which was undetectable gravimetrically. Again, no further analysis was undertaken. Stein et al. (2000) performed the same test on glass, but visual observation and gravimetric analysis did not indicate the presence of any residues. The authors then employed GC-

MS (sensitive to <1 ppb) to confirm the complete sublimation of solvent-delivered CDD and molten CDD from porous stones. Although small quantities were found to linger beyond what was gravimetrically detectable, after exposing the samples to air for several more days no residues were measurable.

These findings contrast with those of Caspi and Kaplan (2001) who reported residues on glass slides and efflorescing brick fragments. In the case of the glass, the residue was minimal; however the ceramics displayed a white, crystalline substance and tidelines following sublimation.

The authors analyzed the residues as well as CDD samples obtained from two different suppliers using FTIR and gas chromatography-mass spectrometry (GC-MS). Impurities were detectable only when the crystals were heated. Caspi and Kaplan showed the residues have a higher molecular weight than CDD and are by-products of its synthesis. The residues were mostly dodecacyclododecane and possibly hydroxydodecacyclododecane with trace amounts of cyclododecane, cyclododecene, cyclododecanone, and cyclododecanol.

Hendry (2001) also observed residues in the form of a ‘powdery white residue’ following the sublimation of CDD from a work of art on paper. The residue was said to be less than one percent of the original mass of CDD applied to the object and unbonded to the support. Hendry noted that a small brush or mini-vacuum was sufficient to remove the residues from the paper.

Parenthetically, there are a limited number of commercial suppliers of cyclododecane.

Kremer Pigments Inc. is the most commonly cited supplier in the literature although CDD may also be obtained from Hans-Michael Hangleiter GmbH, a company founded by one of the original developers of its use for conservation.

CHAPTER 3

EXPERIMENTAL

This study examined the impact of several inherent paper characteristics and common application methods on the rate of CDD sublimation and the detection of residues by analytical and physical means. It was hypothesized that paper characteristics and application methods which promote deeper penetration can slow down the rate of sublimation but that the porosity of papers would not significantly hinder the sublimation process. The paper qualities examined were fiber type, sizing, and surface finish. Several application methods were compared: molten CDD versus a saturated solution in low boiling petroleum ether and molten CDD applied to warmed and unwarmed substrates.

Sublimation of the CDD from the paper substrates was monitored gravimetrically by recording the decrease in total mass over time. This method of tracking permitted accurate quantification of the gradual loss of CDD without interfering with the system under study. Initial attempts to monitor sublimation via Fourier transform infrared spectroscopy (FTIR) with an attenuated total reflectance (ATR) accessory were hindered by the physical displacement of the film by the pressure of the anvils. A non-contact FTIR spectrophotometer would have been a suitable alternative but was unavailable for this study.

After the treated samples returned to their original mass and displayed no visible traces of

CDD, select sample groups from the population were analyzed for residues using GC-FID. The samples were also subjected to water absorbency tests to determine whether this characteristic paper property was fully reestablished. A reduced absorption capacity could be caused by the presence of hydrophobic residues or a possibly a change in the fiber morphology due to heat.

3.1 EVALUATION OF CYCLODODECANE PURITY

The CDD used in this study was obtained from Kremer Pigments Inc. The vendor literature indicated that the product contained no impurities; however, the absence of a certificate of analysis necessitated an independent verification. The purity of the batch was evaluated using four methods of investigation: Fourier transform infrared spectrometry (FTIR) with an attenuated total reflectance

(ATR) accessory, gas chromatography-flame ionization detection (GC-FID), gas chromatography- mass spectrometry (GC-MS) and visual inspection of CDD-coated glass slides following sublimation.

Although FTIR, GC-FID, and GC-MS are far more rigorous methods of characterizing sample purity, the literature does indicate that conservators use and recommend this last method of visual examination to evaluate CDD prior to use (Arenstein et al. 2004; Muros and Hirx, 2004; Stein et al.

2000).

The first purity assessment undertaken in this study was visual examination. Several solid

CDD crystals were placed on two glass slides and heated to 65°C on a hot plate. After the slides were removed from the heat source and the CDD solidified, the circumference of the film was traced with porous pointed pen to eliminate uncertainty of its original position. A Sartorius AC210S analytical balance was used to measure the film mass, which was ~0.70 mg per slide. A micrometer was used to measure the average film thicknesses, which were 0.30 mm and 0.50 mm per slide. The slides were then placed in a fume hood with an airflow rate of ~90 ft3/min as confirmed by a

VelociCalc® Air Velocity Meter (9535-A). The ambient temperature was 21°C ± 1°C and the RH was 55% ± 5%. Four days after application, the glass slides bore no waxy deposits. Inspection of the slides under raking light revealed a distinct, semi-transparent smudge covering the entire area where the CDD had been applied.

A sample of the CDD was then analyzed with a Nicolet Avatar 320 FTIR spectrometer coupled with a Specac Golden Gate™ attenuated total reflectance accessory operating in the mid-

infrared region. Several CDD crystals were placed between the diamond and sapphire anvils and scanned 32 times at a 4 cm-1 resolution in transmittance mode following background collection. The spectral data was processed using GRAMS/32 AI (version 6.00) software.

The resulting infrared spectrum (fig. 3) displayed the characteristic peaks of a hydrocarbon.

The strong, sharp peaks at 2928 cm-1and 2848 cm-1 can be attributed to the antisymmetrical and symmetrical stretching of the C-H bonds, respectively. The two medium peaks at 1470 cm-1 and

1438 cm-1 fall within the range of frequencies produced by the H-C-H bending modes of the methylene groups whereas the strong, sharp peak at 716 cm-1 may be attributed to methylene rocking modes. The series of peaks between 1400 cm-1 and 800 cm-1 cannot be identified individually as they fall within a region of overlapping vibrational frequencies produced by the stretching vibrations of the carbon skeleton and the wagging and twisting modes of methylene groups. A weak peak at

~2660 cm-1, just outside the C-H stretching region, could not be identified. This same peak appears in the CDD reference spectrum from the Integrated Spectral Database System for Organic

Compounds (Japanese National Institute of Advanced Science and Technology). Thus the IR analysis did not indicate the presence of impurities; however, molecular impurities less than 1% are unlikely to be detected by this method of analysis.

100

70 1438

60 1470

50 2848 716

40 2928

3500 3000 2500 2000 1500 1000 500 wavenumber (cm-1)

Fig. 3: FTIR spectrum of cyclododecane

As visual examination suggested the presence of a non-volatile impurity, the experimental

CDD was further characterized with an Agilent Model 6890 gas chromatograph coupled with a flame ionization detector (GC-FID). GC-FID is exceptionally well suited for the analysis of hydrocarbons and this particular instrument has a detection limit of < 10 µg. The purity of a sample is usually established by comparing its retention time against a known standard; however, at the time of this research no commercial source of CDD in North America provided a certificate of analysis.

Consequently, the purity of the CDD was determined based on the number of elutions with a single peak suggesting a pure substance. Although GC-FID cannot identify the components in a mixture it can provide quantitative information about the number of impurities and their masses.

Analyses were carried out on 400 ppm, 40 ppm, and 4 ppm CDD standard solutions prepared in hexane. The injector and detector temperatures were 225ºC and 300ºC, respectively. A

1-µL volume of each sample was injected into the GC via an automatic injection system (Agilent

7683 Series Autosampler Injector) operated in splitless mode to maximize the detection of trace elements. The GC was equipped with a Supelco SPB-1 fused silica capillary column (30 m x 0.25 mm I.D.) with a stationary phase of bonded polydimethyl siloxane (0.25 µm). The carrier gas was helium with an inlet pressure of 17.3 psi and a flow rate of 1-2 mL/min. The oven temperature was set initially to 40°C for a six-minute hold then increased by 10°C/min until reaching 150°C. The temperature was then increased by 12°C/min until reaching 280°C then maintained for 20 minutes.

The total run time was 48 minutes.

In this analysis the chromatogram displayed a single peak at 16 minutes suggesting a pure substance. This result was later called into question when subsequent runs using the same CDD standards for calibration showed several traces around the dominant CDD peak (fig. 4). These traces were detected using the same Agilent GC-FID as well as a Hewlett-Packard Model 5890 (Series II)

GC-FID. All of the traces were less than 7 ppm and had retention times between 15 and 17 minutes depending on which GC was used.

Fig. 4: Detail of GC-FID chromatogram of cyclododecane

These findings prompted a final analysis of the CDD with a Waters gas chromatograph coupled with a time-of-flight mass spectrometer (GC-TOF-MS) operated in electron ionization mode (polarity EI+). The CDD was combined with methanol and a 1-µL volume of the solution was introduced to the GC-TOF-MS with a probe. The EI source temperature was 180°C and the emission current was 416.4 µA. The electron energy was 16.0 eV – significantly lower than the standard 70 eV – in order to analyze intact molecular ions as opposed to fragmented species. The voltage of the multi-channel plate detector was 2800. As seen in figure 5, the chromatogram did not reveal any peaks suggestive of higher molecular weight impurities in the CDD sample. It was

concluded that the residues on the glass slides were on the order of microns and the amount of impurities in the Kremer CDD was negligible i.e., below the detection capabilities of GC-MS.

26 !

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SHG20130730-CYCLODODECANE SHG20130730-CYCLODODECANE (0.017) Is (1.00,1.00) C12H24 TOF MS EI+ 168.1878 100 8.73e12 ISOTOPE MODEL - EI

Fig. 5: GC-MS chromatogram169.1912 of cyclododecane

0 SHG20130730-CYCLODODECANE 36 (0.600) Cm (36:46) TOF MS EI+ 168.1873 100 1.81e3 HIGH RES. - EI

169.1940

153.8596 162.1416 166.1732 166.6876 170.1896 172.0632 0 m/z 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 ! !

3.2 GRAVIMETRIC PROCEDURES TO DETERMINE CDD SUBLIMATION RATES

The rate of CDD sublimation was determined gravimetrically as a function of weight loss over time. A Sartorius AC210S analytical balance sensitive to four decimal places was employed in all tests. Temperature and RH were recorded hourly during the experiments with a HOBO Onset

U14-001 data logger. Changes in the total mass due to fluctuating RH were tracked by weighing controls for each paper type. Although the CDD-coated samples may have exhibited different moisture absorption capacities, the magnitude of the change observed in the controls would serve to illustrate the upper limits of the absorption. The moisture content of paper is typically 6%-7% at

50% RH.

EXPERIMENT 1: FIBER TYPE

The first gravimetric test examined the influence of fiber type on sublimation. It was hypothesized that fiber type alone would not significantly impact the sublimation of CDD from the substrate surface; however, the density of the fiber network and the extent of fibrillation could impact the subsurface retention of the CDD. Four modern papers were selected, each consisting of a single fiber type: cotton, flax, kozo, and groundwood. The papers, respectively, were Whatman filter paper #1, a handmade flax paper produced by Cave Paper Inc., a handmade Inoue Haini kozo paper, and Canson newsprint. None of the papers were sized nor did they contain any fillers or auxiliary materials.

Twenty samples of each paper type were used for a total of eighty samples. An equal number of controls were also monitored. All samples and controls in this test and all subsequent tests measured 5 x 5 cm. Each sample and control was marked in graphite with a unique code and weighed on a Sartorius AC210S analytical balance to four decimal places. The average initial mass and thickness of each sample type (n=20) are given in table 2 along with the standard deviations and

standard errors. The cotton and flax samples weighed ~0.2249 g and ~0.2829 g, respectively, whereas the lighter kozo and groundwood samples weighed ~0.0845 g and ~0.1225 g, respectively.

The average paper thicknesses were similarly bifurcated with the cotton and flax papers measuring

~0.20 mm and ~0.28 mm, respectively, and the thinner kozo and wood fiber papers measuring

~0.10 mm and ~0.13 mm.

TABLE 2: AVERAGE INITIAL MASS AND THICKNESS OF COTTON, FLAX, KOZO, AND GROUNDWOOD FIBER PAPER SAMPLES AND CYCLODODECANE APPLIED AS A MELT

Paper CDD Sample Mass SD Thickness SD Mass SD Thicknessa SD Type (g) SE (mm) SE (g) SE (mm) SE

Cotton 0.2249 0.003 0.20 0.007 0.1581 0.004 0.0007 0.002 0.0008

Flax 0.2829 0.004 0.28 0.02 0.1664 0.005 0.37 0.09 0.0009 0.004 0.001 0.02

Kozo 0.0845 0.003 0.10 0.005 0.1648 0.008 0.0005 0.001 0.002

Wood 0.1225 0.001 0.13 0.005 0.1647 0.004 0.0003 0.001 0.0009

Note: n=20 for all averages except CDD thickness where n=80. aAverage CDD thickness is representative for all sample types.

Approximately 0.16 g of molten CDD was applied to one side of the sample with an electric kistka covering a 2.0 x 5.0 cm area. A glass template was used to ensure uniform distribution across the samples although variations in thickness were unavoidable. These variations in the film thickness were comparable across all sample units and paper types. To expedite sample preparation, the brass tip of the kistka was enlarged to 1 mm in diameter and a brass reservoir with a 2.4-cm3 volume was welded onto it (fig. 6). A rheostat was coupled with the kistka to maintain the temperature at 70°C

±3°C. Samples were weighed immediately after solidification of the cyclododecane. Thereafter, the

samples were weighed three times daily at three-hour intervals until they returned to their original mass and displayed no waxy deposits. The controls were weighed once daily.

Fig. 6: Modified electric kistka

The average initial mass and thickness of the CDD films are given in table 2 along with the standard deviations and standard errors. Similar values are seen across the paper types: cotton

(0.1581 g of CDD), flax (0.1664 g of CDD), kozo (0.1648 g of CDD), and groundwood (0.1647 g of

CDD). The average initial thickness of the films was 0.37 mm.

The samples and controls were placed on aluminum trays lined with polyester film and stored on horizontal racks in a fume hood (fig. 7). The trays were arranged perpendicular to the sash of the fume hood with 10 cm of airspace above each tray. A VelociCalc® anemometer (Model 9535-

A) detected zero airflow over the samples. The lack of air circulation over the samples should not, however, inhibit the sublimation of CDD due to the size-volume ratio between the samples and the fume hood. The trays were rotated on the racks daily to eliminate any biases in positional variances.

Fig. 7: Arrangement of Samples and Controls in Fume Hood

EXPERIMENT 2: SIZED AND WATERLEAF PAPERS

The second test examined the impact of sizing on the rate of sublimation. The samples were composed of pure flax fibers with no fillers or additives. One sample set was unsized and the other was externally sized with gelatin by the manufacturer Cave Paper Inc. (2.5% dry weight). The experimental procedures mirrored those described for the first experiment with molten CDD applied to a 2 x 5 cm area of the samples using an electric kistka. Twenty repetitions were performed for both paper types for a total of 40 samples. An equal number of sized and waterleaf controls were also monitored. As shown in table 3, the waterleaf and gelatin-sized papers were similar in weight

(0.39 g) and thickness (0.38 mm and 0.35 mm). The average initial mass of CDD on each sample type was 0.11 g and the average thickness was 0.22 mm.

TABLE 3: AVERAGE INITIAL MASS AND THICKNESS OF WATERLEAF AND GELATIN-SIZED FLAX PAPER SAMPLES AND CYCLODODECANE APPLIED AS A MELT

Paper CDD Sample Mass SD Thickness SD Mass SD Thicknessa SD Type (g) SE (mm) SE (g) SE (mm) SE

Waterleaf 0.3980 0.008 0.38 0.03 0.1144 0.004 0.002 0.007 0.0008 0.22 0.10 0.02 Gelatin-sized 0.3959 0.003 0.35 0.03 0.1140 0.003 0.0007 0.007 0.0006 Note: n=20 for all averages except CDD thickness where n=40. aAverage CDD thickness is representative for both sample types.

EXPERIMENT 3: FINISHES

The influence of surface texture on the rate of sublimation was assessed on three papers of identical composition, but with distinct surface characteristics: cold pressed, hot pressed, and rough finish. The papers were from the Artistico series of mouldmade papers by C. M. Fabriano and were composed of pure cotton fibers, neutral pH, white, 200 g/m2, with synthetic internal and external sizing. FTIR analysis revealed the presence of calcium carbonate. The aforementioned experimental procedures were repeated on 20 samples of each finish type for a total of 60 samples. An equal number of controls were also weighed throughout the test period. The average mass and thickness of the samples are given in table 4, together with the average initial mass and thickness of CDD film as well as the standard deviations and standard errors. The papers were of comparable weight (0.49 g to 0.52 g) and thickness (0.28 mm to 0.36 mm). The mass of CDD film on each sample type was

~0.1 g and the average thickness of the layer was 0.25 mm.

TABLE 4: AVERAGE INITIAL MASS AND THICKNESS OF COLD PRESSED, HOT PRESSED, AND ROUGH PAPER SAMPLES AND CYCLODODECANE APPLIED AS A MELT

Paper CDD Sample Mass SD Thickness SD Mass SD Thicknessa SD Type (g) SE (mm) SE (g) SE (mm) SE

Cold pressed 0.5208 0.005 0.36 0.006 0.1052 0.004 0.001 0.001 0.0008

0.25 0.09 Hot pressed 0.5082 0.003 0.28 0.006 0.1035 0.003 0.03 0.0007 0.001 0.0007

Rough 0.4961 0.003 0.35 0.004 0.1057 0.002 0.0006 0.0009 0.0005 Note: n=20 for all averages except CDD thickness where n=60. aAverage CDD thickness is representative for all sample types.

EXPERIMENT 4: WARMED AND UNWARMED SUBSTRATES

The fourth gravimetric test examined whether warming the substrate has an appreciable effect on the sublimation of CDD. Scharff and Nielsen (2003) reported that CDD functioned most effectively as a hydrophobic barrier when applied to both sides of paper warmed to ~40ºC. Since elevated temperatures can damage paper this application technique could be considered controversial; however, because of the short duration of exposure (several minutes or less depending on substrate thickness) and its use by conservators to both apply CDD and to expedite its sublimation, this application method was included in this study. Because this technique appears to drive the cyclododecane much further into paper than other application methods with the possible exception of CDD-saturated solutions in high-boiling solvents, it was hypothesized that it would exhibit the slowest rate of sublimation at the surface and subsurface levels.

The paper used in this experiment was Whatman filter paper #1. Twenty samples were warmed approximately two minutes before and during the application of molten CDD while another 20 samples were treated at room temperature. Twenty controls were also monitored to assess the effects of RH on the total mass of the sample population.

As shown in table 5, the average mass of the paper samples was ~0.2250 g and the average thickness was 0.18 mm; the standard deviations and standard errors were also given. The same amount of molten CDD was applied to both the heated and unheated groups (~0.1064 g). The samples in the heated group were placed on unprinted bond waste paper and warmed for approximately three minutes on a Fisher Scientific Model 77 slide warmer. Molten CDD was applied through a glass template over a 2 x 5 cm area while the samples were still in contact with the heat source. The temperature of the slide warmer was maintained at 40ºC ±2ºC. A FLUKE 51 thermocouple was used to monitor the temperature across the slide warmer to ensure uniformity.

The average thickness of the warmed samples was approximately half of thickness of the unwarmed samples.

TABLE 5: AVERAGE INITIAL MASS AND THICKNESS OF WHATMAN FILTER PAPER SAMPLES AND CYCLODODECANE APPLIED AS A MELT ONTO UNWARMED AND WARMED SUBSTRATES

Paper CDD Sample Mass SD Thickness SD Mass SD Thicknessa SD Type (g) SE (mm) SE (g) SE (mm) SE

Unwarmed 0.2256 0.003 0.18 0.006 0.1065 0.004 0.31 0.01 0.0006 0.001 0.0008 0.02

Warmed 0.2249 0.002 0.18 0.007 0.1063 0.003 0.15 0.06 0.0005 0.002 0.0006 0.01 Note: n=20 for all averages

Fig. 8: Warming of paper samples Fig. 9: Detail of paper samples with templates and slide warmer

Fig. 10: Molten CDD applied to unwarmed Fig. 11: Molten CDD applied to warmed Whatman Whatman filter paper #1 filter paper #1

EXPERIMENT 5: MOLTEN CDD AND CDD-SATURATED SOLUTION

The final gravimetric test compared the sublimation rates of CDD applied as a melt and as a saturated solution in low-boiling petroleum ether to Fabriano Artistico Rough paper. Conservation studies examining the use of CDD as a hydrophobic barrier found that the molten form produces the most impermeable film; however, Jägers and Jägers (1999) maintain that CDD can be similarly effective in solutions of low-boiling solvents and have recommended the use of petroleum ether in

particular. As noted in Chapter 2, the crystals formed by CDD-saturated solutions in low-boiling solvents are small and densely packed somewhat akin to those formed by the melt. The crystals formed from such solutions also tend to cluster predominantly on the substrate surface. Although the penetration of molten CDD into paper has not been measured, it is speculated that it would be moderate unless the substrate was warmed. It was therefore hypothesized that the two methods of application ⎯ the molten CDD and the CDD-saturated solution in low-boiling petroleum ether ⎯ would share similar sublimation rates due to similar crystal size and comparable penetration capacities. This test did not include a CDD-saturated solution in a high-boiling solvent because the resulting films, composed of larger, more loosely packed crystals, offer less protection to the underlying substrate and this method is infrequently used in the conservation of paper-based objects.

Twenty samples were treated with molten CDD and twenty samples were treated with a

CDD-saturated solution for a total of 40 samples. In both sample sets, the substrate was Fabriano

Artistico Rough, a pure cotton fiber paper with synthetic internal and external sizing. The molten

CDD was applied with an electric kistka following the procedures specified in the first gravimetric experiment. The saturated solution was prepared by dissolving 10 g of CDD in 10 mL of petroleum ether (b.p. range 30°C-40°C) and administered via glass pipettes. Both the molten CDD and the

CDD-saturated solution were applied to a 2.5 x 2.5 cm central area of the sample, the outline of which was demarcated with graphite. A smaller test area was used in this experiment in order to prevent the solution from spreading over the sample edges and thereby reducing the total mass of

CDD deposited.

Prior to applying the solution, each sample was placed on a 10 x 10 cm aluminum support with a 4-cm diameter hole cut from the center. The support and paper were placed over a glass bowl

(concave side up) to provide a 10-cm clearance below the paper (fig. 12). A 0.10 mL volume of the solution was then applied to each sample. By suspending the paper in this manner the full volume

was absorbed by the paper i.e., none of the CDD penetrated through the paper and accumulated on the surface below. This step may have been unnecessary due to the rapid evaporation of the solvent, but was adopted as a precaution.

The samples were then suspended from a cotton line with miniature plastic clips in a fume hood for the duration of the test period (fig. 13). The rate of sublimation was calculated from measurements taken twenty-one hours after the solution was applied to allow sufficient time for the solvent to completely evaporate and the CDD solidify. The average mass and thickness of the CDD after twenty-one hours, as given in table 6, was 0.0485 g and 18 mm, respectively. This average mass is comparable to the mass used in the molten application, which displayed an average initial mass of

0.0503 g and an average initial thickness of 0.20 mm. All the standard deviations and standard errors were also given. The samples prepared with molten CDD were suspended in the fume hood in the same manner as the samples treated with the CDD-saturated solutions. The airflow rate in the fume hood was ~90 ft3/min as confirmed by a VelociCalc® Air Velocity Meter (9535-A).

TABLE 6: AVERAGE INITIAL MASS AND THICKNESS OF WHATMAN FILTER PAPER SAMPLES AND CDD APPLIED AS A MELT AND A SATURATED SOLUTION IN PETROLEUM ETHER (30°C-40°C)

Paper CDD Sample Mass SD Thickness SD Mass SD Thicknessa SD Type (g) SE (mm) SE (g) SE (mm) SE

Molten 0.4972 0.003 0.35 0.007 0.0503 0.002 0.20 0.09 0.0007 0.002 0.0003 0.02

Saturated 0.4972 0.003 0.35 0.004 0.0485 0.009 0.18 0.04 0.0006 0.001 0.002 Solution 0.009

Note: n=20 for all averages

Fig. 12: Device for applying CDD-saturated Fig. 13: Suspension of samples prepared with molten solution CDD and CDD-saturated solution

3.3 GC-FID PROCEDURES TO TEST FOR THE PRESENCE OF RESIDUES

Gas chromatography-flame ionization detection analyses were performed on select samples that had undergone gravimetric monitoring of their sublimation. Analyses were carried out between

12 to 36 hours after the samples returned to their untreated weight in order to determine whether complete sublimation had occurred. Two samples from each of the following populations were analyzed: (1) waterleaf flax paper treated with molten CDD; (2) gelatin-sized flax paper treated with molten CDD; (3) Whatman filter paper treated at room temperature with molten CDD; (4)

Whatman filter paper treated at 40ºC with molten CDD; (5) Artistico rough finish paper treated with molten CDD; and (6) Artistico rough finish papers treated with a CDD-saturated solution in low- boiling petroleum ether. Untreated controls, CDD-spiked controls, and CDD standard solutions

(400 ppm, 40 ppm, and 4 ppm in hexane) were analyzed concurrently with the samples. The approximate recovery rates for the spiked controls were calculated from the standard factors.

Specimens were rolled up and inserted into 16-mL glass vials to which 10 mL of hexane was added. As CDD is readily soluble in organic solvents, the hexane dissolved any crystals remaining

within the paper. The vials were capped, then gently shaken for 2-3 minutes, and allowed to set for several hours prior to analysis. The extractions were then transferred with glass pipettes into 2-mL glass vials for auto-injection.

The majority of the samples were analyzed using a Hewlett-Packard Model 5890 (Series II)

GC-FID; however, the Artistico papers treated with molten CDD and a CDD-saturated solution were analyzed with an Agilent Model 6890 GC-FID. Both instruments have a detection limit of < 10

µg. Each GC was equipped with a 30 m SPB-1 Supelco fused silica capillary column with bonded polydimethylsiloxane (0.25 mm I.D. and 0.25 µm film thickness). A 1-µL volume of the hexane solutions was injected into the Agilent GC-FID and a 2-µL volume was injected into the Hewlett-

Packard GC-FID. Auto-injections were performed in the splitless mode. The carrier gas was helium with an inlet pressure of 17.3 psi and a flow rate of 1-2 mL/min. The oven temperature was initialized to 40°C for a six-minute hold followed by an increase of 10°C/min until reaching 150°C.

The temperature was then increased 12°C/min until reaching 280°C then maintained for 20 minutes.

The total run time was 47.83 minutes.

3.4 WATER ABSORBENCY TESTS

The conservation literature has reported that the effectiveness of CDD as a hydrophobic barrier is contingent on the size and density of the crystals as well as the inherent characteristics of the paper. Since CDD renders the paper less hygroscopic, any discrepancies in the absorption capacity of the CDD-treated samples compared to controls may be due to the presence of hydrophobic residues or changes in the morphology of the fibers. This test examined whether the water absorption characteristics of papers treated with CDD are fully reestablished after complete sublimation.

Water absorbency tests were carried out on the following samples, which had previously undergone gravimetric monitoring of their sublimation: (1) waterleaf and gelatin-sized flax papers treated with molten CDD, (2) unwarmed and warmed Whatman filter papers treated with molten

CDD, and (3) Whatman filter paper treated with molten CDD and CDD-saturated solution in low boiling petroleum ether. Fifteen samples from each sample type were tested for a total of 90 samples.

An equal number of controls of each paper type were tested concurrently with their sample counterparts.

The water absorbency tests on unsized samples and controls were performed according to

TAPPI Test Method T432 cm-09: Water Absorbency of Bibulous Papers. The test method describes procedures for measuring the length of time required for a given volume of water to be absorbed by unsized paper. Absorbency tests on the sized samples and controls were performed using a modified version of TAPPI test method T441 om-09: Water Absorptiveness of Sized (Non-Bibulous) Paper,

Paperboard, and Corrugated Fiberboard (Cobb Test).

The environmental conditions under which the samples were preconditioned, conditioned, and tested followed TAPPI Test Method T402: Standard Conditioning and Testing Atmospheres for Paper,

Board, Pulp Handsheets, and Related Products. The preconditioning process served to prevent potential biases in the moisture content of papers due to humidity hysteresis (variations in the moisture content of the samples caused by the temperature of their pretesting environment). In this study preconditioning occurred in a sealed chamber, which TAPPI T402 recommends to be kept at 12-

13% RH and 23 ±1°C. The suggested conditioning and testing environment is 50.0% ± 2.0% RH and 23.0 ± 1.0°C. Each set of samples and controls were preconditioned simultaneously and then conditioned and tested in short succession to ensure exposure to the same environmental conditions.

All samples and controls were preconditioned for approximately forty-eight hours in an airtight, glass chamber with interior dimensions of 53 x 30 x 20 cm. The samples and controls were

arranged on two plastic honeycomb trays stacked horizontally with 6-cm clearance above and below to ensure both sides of the papers were uniformly exposed. A relative humidity of 11%-13% was established and maintained through a simple dehumidification system (fig. 14). An Optima aquarium pump was used to force air through a desiccator and then into the chamber via plastic tubing inserted into an aperture in the lid. Dry air was thus introduced into the chamber while a second aperture fitted with a plastic tube permitted the escape of moist air. When the correct RH was reached, the apertures were plugged with rubber stoppers. Clamps and grease applied along the edges of the lid helped ensure an airtight seal. A lithium chloride-saturated solution in the chamber maintained the RH as the papers desorbed moisture to achieve equilibrium. A HOBO Onset data logger recorded the temperature and RH within the chamber.

Fig. 14: Preconditioning chamber

Following preconditioning, the samples and controls were acclimatized at the test room temperature and RH for approximately one hour or until reaching equilibrium with the surrounding environment. Tests were not conducted until the weight of the paper stabilized. Although fluctuations in the test room temperature and RH did not occur within the span of a given test

category, they did vary between the three test categories. These changes ranged from 21°C-23°C and

50%-60% RH.

The water absorbency tests performed on the unsized samples and controls consisted of the following procedures. Each paper was placed on a 10 x 10 cm aluminum support with a 4-cm diameter hole in the center. The support and paper were then placed on top of a glass bowl to provide a 10-cm clearance directly below the paper (fig. 12). By suspending the paper in this manner the full volume of water would be absorbed by the paper. Deionized water was dispensed as rapidly as possible from a hypodermic syringe onto the center of each sample and control. A 0.05 mL volume was applied to samples and controls of Whatman filter paper and a 0.1 mL volume was applied to samples and controls of the unsized flax paper. A stopwatch was used to measure the time required for the paper to absorb the water fully. A light was trained on the droplet to view the reflected light; lack of reflection was used to determine the point at which full absorbance occurred.

The light was held at a distance of ~12 cm to prevent the water from evaporating due to heat generated by the light.

To determine whether the sized papers underwent a change in water absorbency, a modified test based on TAPPI Test Method T441 Water Absorptiveness of Sized (Non-Bibulous) Paper, Paperboard, and Corrugated Fiberboard (Cobb Test) was used to measure the amount of water absorbed by a sized paper within a defined period of time. The test required specialized apparatuses for administering the water and for wicking unabsorbed water from the sample surface. The unavailability of these apparatus necessitated several adjustments to the protocol without compromising the overarching experimental design. The most significant adjustment was that a reduced volume of water was applied to a smaller area of the samples and controls.

Water absorbency tests on the gelatin-sized samples and controls consisted of the following procedures. Each specimen was weighed on a Sartorius BP211D analytical balance and its mass

recorded. The sample was then placed on a clean glass sheet and 0.1 mL of deionized water was applied with a hypodermic syringe to the center of the paper from where the CDD had sublimed.

The droplet was then covered with a 9-cm diameter petri dish to prevent evaporation and left undisturbed for exactly 120 seconds. Immediately afterward, the paper was covered with a 0.65 mm thick blotter square and a 36 g glass weight was placed on top for exactly five seconds to absorb excess water from its surface. The paper was then immediately weighed again. The difference between the final and initial masses is the amount of water in grams absorbed by the paper in 120 seconds.

It should be noted that several samples included in the water absorbency tests displayed minute, waxy deposits immediately prior to preconditioning; however they were no longer discernible after preconditioning. The samples were included in the tests to provide the maximum possible sample population from among those used in the gravimetric experiments.

CHAPTER 4

RESULTS AND DISCUSSION

4.1 Gravimetric Analyses

Initial analysis of the gravimetric data focused on finding the best curve fit to describe the sublimation rates across sample groups. Attempts to locate the best model were made using R (R

Project for statistical computing, Vienna, Austria) and JMP (SAS Institute, Inc.) statistical software.

Linear regression, polynomial, double exponential, and exponential decay curves failed to provide a good fit across the sample types. Undoubtedly, the best curve fit could be discovered given more time; however, this problem was unable to be solved within the timeframe of this project. Ultimately the data was analyzed in Excel (Microsoft Corporation), which permitted sufficient accuracy and flexibility to compare the sublimation rates among the sample categories.

The sublimation rates of CDD were compared using three methods of analysis. Firstly, the mean values for the total mass loss were plotted over time i.e., the initial mass of paper with CDD minus the mass of paper with CDD at set points in time (figs. 15, 17, 19, 21, 23). Each of the data points in the graphs represents the mean of 20 measurements, each taken from a different sample

(20 samples in total). Total mass was used in preference to CDD mass because it more accurately described the weight changes to the samples including those due to varied moisture content. In contrast, the gradual loss of CDD could only be approximated by subtracting the initial (changeable) paper mass from that of the total mass over time. Although the samples exhibited minimal weight changes due to the absorption and desorption of moisture (appendix 3) and similar trend lines were observed in plots of both total mass and CDD mass, the former was used in the interest of accuracy.

The gravimetric data was further analyzed by plotting the mean values for the total mass

(paper with CDD) against time (figs. 16, 18, 20, 22, 24). These graphs showed the same sublimation

trends as the plots of total mass loss, but facilitated examination of the standard deviations (SDs), which would otherwise be obscured by overlapping trend lines. Each error bar represents the SDs calculated from the mean of 20 measurements, each taken from a different sample (20 samples in total). The SDs unavoidably reflect variations in moisture content and cannot be interpreted solely as deviations in CDD mass.

Finally, the percent mass loss of CDD was calculated for each sample group wherein each value represents the mean of 20 measurements taken at 24 hours intervals (tables 7, 8, 9, 10, 11).

These results are presented along with the average initial mass of CDD for ease of comparing the time required for complete sublimation to occur under the given experimental conditions. It is important to realize that the unrecovered percentages cannot be attributed solely to CDD residues.

As will be clear from the GC-FID results, changes in moisture content were the primary reason the percent mass loss did not consistently reach 100% by the end of the test period. It bears worth repeating that the gravimetric measurements ceased to be collected once the majority of samples returned to their original weight or bore no visual evidence of CDD. Despite these caveats, the percent mass loss does provide useful information about the length of time required for complete sublimation to occur under the test conditions.

The mean sublimation rates of CDD, applied as a melt, from unsized cotton, flax, kozo, and groundwood papers are presented in figure 15. The slope of the line is similar across sample types indicating that fiber morphology does not appreciably affect the rate of sublimation. The smaller total mass loss for the cotton fiber paper can be attributed to the smaller amount of CDD applied

(table 7) as opposed to a greater retention of CDD. This interpretation of the data is borne out by comparing the percent mass loss for the four fiber types. As seen in table 7, the difference between the samples was <1% with cotton sharing the same loss as kozo (99.7%) and a comparable loss to groundwood (99.5%). Moreover, plots of the controls v. temperature and RH show that moisture

caused insufficiently dissimilar mass changes to account for the smaller total mass loss of the cotton samples (appendix 3).

Although the effect of paper thickness on the sublimation rate of CDD was not examined in this study, the roughly two different thicknesses among the four fiber types (see table 2) provided the opportunity to observe its impact as well. The results suggested that paper thickness, like fiber type, had no effect on the sublimation rate of CDD when applied in the molten state.

Figure 16 shows that the standard deviations of the measurements were comparable across the fiber types. The smaller SD values in the final hours of the test reflect the smaller amount of

CDD remaining on the samples. This trend of diminishing SDs does not occur in all of the other plots of total mass loss, as the RH fluctuated more widely during the other tests (appendix 2).

Fig. 15: Mean sublimation rates of CDD, applied as a melt, from unsized cotton, flax, kozo, and groundwood papers plotted as a function of total mass loss against time. Each data point represents the average of 20 measurements.

0.1800

0.1600

0.1400

0.1200

0.1000

0.0800 Cotton

0.0600 Flax

0.0400 Kozo

Total Mass Loss of Mass Loss Total (g) CDD and Paper 0.0200 Wood

0.0000 0 24 48 72 96 120 144 168 192 216 240 Time (hr)

Fig. 16: Mean sublimation rates of CDD from cotton, flax, kozo, and groundwood papers plotted as a function of total mass against time with error bars showing standard deviations for the average of 20 measurements

0.5000

0.4500 Cotton Flax 0.4000 Kozo 0.3500 Wood

0.3000

0.2500

0.2000

0.1500

0.1000 Total Mass ofTotal (g) CDD and Paper 0.0500

0.0000 0 24 48 72 96 120 144 168 192 216 240 Time (hr)

TABLE 7: AVERAGE PERCENT MASS LOSS OF CDD FROM COTTON, FLAX, KOZO, AND GROUNDWOOD PAPERS OVER TIME. AVERAGE INITIAL CDD MASSES ARE GIVEN WITH STANDARD DEVIATIONS AND STANDARD ERRORS. ALL AVERAGES WERE CALCULATED FROM 20 REPLICATES PER SAMPLE GROUP.

Cotton Flax Kozo Wood Days Average Percent Mass Loss of CDD 1 22.0% 20.5% 23.0% 23.0% 2 47.5% 41.9% 44.9% 44.7% 3 67.6% 62.9% 66.3% 64.1% 4 85.0% 80.0% 82.1% 80.9% 5 94.5% 92.3% 93.3% 91.9% 6 97.9% 96.8% 98.1% 97.1% 7 99.1% 98.4% 99.6% 99.0% 8 99.7% 99.1% 99.7% 99.5% Average Initial CDD Mass (g) M 0.1581 0.1664 0.1648 0.1647 SD 0.004 0.005 0.008 0.004 SE 0.0008 0.001 0.002 0.0009

The mean sublimation rates of CDD, applied as a melt, from handmade waterleaf and gelatin-sized flax papers are shown in figure 17. The slope of the line is nearly identical between the two sample groups suggesting that sublimation is not affected by the presence of sizing. It had been surmised that the CDD would penetrate further into the waterleaf samples resulting in a slower rate of sublimation (assuming that CDD sublimes more slowly from below the paper surface). The results of this gravimetric test indicated that one or both of these hypotheses were incorrect.

Cryogenic-SEM imaging of the cross-sections of the samples directly following the application of

CDD would have been useful for discovering the depth of penetration. It remains unclear whether there was any difference in penetration or whether the porosity of the papers simply did not hinder sublimation.

Figure 18 shows the change in total mass over time with SDs for the mean of 20 measurements. The larger SD values are most likely due to wider RH fluctuations (3% to 10% per day); nearly double those that occurred during the first gravimetric experiment (appendix 2). Not surprisingly, the SDs were larger for the more water absorbent, unsized papers. Table 8 shows a comparable percent mass loss between the two sample groups (a difference of <1%). The shorter sublimation time observed between this gravimetric test and the previous one can be attributed to a

50 mg reduction in CDD applied.

Fig. 17: Mean sublimation rates of CDD, applied as a melt, from waterleaf and gelatin-sized flax papers plotted as a function of total mass loss against time. Each data point represents the average of 20 measurements.

0.1200

0.1000

0.0800

0.0600

0.0400 Waterleaf 0.0200 Gelatin-Sized

0.0000 Total Mass Loss of Mass Loss Total (g) CDD and Paper 0 24 48 72 96 120 144

Time (hr)

Fig. 18: Mean sublimation rates of CDD from waterleaf and gelatin-sized flax papers plotted as a function of total mass against time with error bars showing standard deviations for the average of 20 measurements

0.53

0.51 Waterleaf

0.49 Gelatin-Sized

0.47

0.45

0.43

0.41

Total Mass ofTotal (g) CDD and Paper 0.39

0.37 0 24 48 72 96 120 144 168

Time (hr)

TABLE 8: AVERAGE PERCENT MASS LOSS OF CDD FROM WATERLEAF AND GELATIN-SIZED FLAX PAPERS OVER TIME. AVERAGE INITIAL CDD MASSES ARE GIVEN ALONG WITH THE STANDARD DEVIATIONS. ALL AVERAGES WERE CALCULATED FROM 20 REPLICATES PER SAMPLE TYPE.

Waterleaf Flax Gelatin-Sized Flax Days Average Percent Mass Loss of CDD 1 38.5% 36.8% 2 70.7% 71.4% 3 88.5% 88.1% 4 95.3% 94.3% 5 98.1% 98.5% 6 102.0% 101.6% Average Initial CDD Mass (g) M 0.1144 0.1140 SD 0.004 0.003 SE 0.0008 0.0006

The average sublimation rates of CDD, applied as a melt, from cold pressed, hot pressed, and rough finish Fabriano Artistico papers are presented in figure 19. All of the papers were machine-made, composed of cotton fibers, and synthetically sized. Again, the slope of the line is similar across sample types suggesting that surface finish does not appreciably impact the rate of sublimation. It had been hypothesized that the rough and cold pressed finishes would facilitate penetration of the CDD, resulting in slower sublimation rates than those observed from the hot pressed samples. These results suggest that the depth of penetration was comparable or the porosity of the samples did not present a substantive barrier to sublimation.

The standard deviations for the total mass over time were similar across paper types (figure

20). The relatively large SDs were most likely due to widely varying RH during the course of this experiment; changes ranging from 3% to 14% per day (appendix 2). It is worth noting that RH is not expected to influence the rate of sublimation. Only one study (Arenstein et al. 2004) mentions

RH as a contributing factor in sublimation, but no citations were provided as supporting evidence.

RH has been shown, however, to affect the dispersion of CDD vapors (Vernez et al. 2011).

Theoretically localized pockets of vapor phase CDD could have formed above the samples due to their stacked configuration (fig. 7); however, the size-volume ratio between the samples and the fume hood was expected to alleviate any potential influence this might have on the sublimation rate.

The percent mass loss of CDD was consistent across sample groups (table 9) reinforcing the conclusion that surface finish plays a negligible role in sublimation below the paper surface. It was surmised that the unrecovered percentages are due primarily to moisture absorption. Minute amounts of CDD (~ less than 1 mg) were still visible on three of the cold pressed samples, five of the hot pressed samples, and two of rough finish samples at the end of the test period, but these traces would not account for the approximate 6% difference between the initial and final masses.

Fig. 19: Mean sublimation rates of CDD, applied as a melt, from cold pressed, hot pressed, and rough finish Fabriano Artistico papers plotted as a function of total mass loss against time. Each data point represents the average of 20 measurements.

0.1200

0.1000

0.0800

0.0600

0.0400 Cold Pressed Hot Pressed 0.0200 Rough

Total Mass Loss of Mass Loss Total (g) CDD and Paper 0.0000 0 24 48 72 96 120 144 Time (hr)

Fig. 20: Mean sublimation rates of CDD, applied as a melt, from cold pressed, hot pressed, and rough finish Fabriano Artistico papers plotted as a function of total mass against time with error bars showing standard deviations for the average of 20 measurements

0.6500

Cold Pressed 0.6300 Hot Pressed 0.6100 Rough 0.5900

0.5700

0.5500

0.5300 Total Mass ofTotal (g) CDD and Paper

0.5100

0.4900 0 24 48 72 96 120 144 Time (hr)

TABLE 9: AVERAGE PERCENT MASS LOSS OF CDD OVER TIME FROM COLD PRESSED, HOT PRESSED, AND ROUGH FINISH FABRIANO ARTISTICO PAPERS. AVERAGE INITIAL CDD MASSES ARE GIVEN ALONG WITH THE STANDARD DEVIATIONS. ALL AVERAGES WERE CALCULATED FROM 20 REPLICATES PER SAMPLE TYPE.

Cold Pressed Hot Pressed Rough Days Average Percent Mass Loss of CDD 1 37.6% 37.9% 35.9% 2 68.2% 69.1% 67.3% 3 88.9% 88.1% 87.1% 4 91.3% 92.5% 92.8% 5 92.6% 93.7% 93.6% Average Initial CDD Mass (g) M 0.1052 0.1035 0.1057 SD 0.004 0.003 0.002 SE 0.0008 0.0007 0.0005

The average sublimation rates of CDD, applied as a melt, to warmed and unwarmed

Whatman filter paper samples are shown in figure 21. The warmed samples had been heated to

~40°C several minutes before and during the application of the CDD. The trend lines show that the warmed samples lost less CDD than the unwarmed samples during the first two days after application, but by the fourth day the losses were comparable (figs. 21 and 22). This result was surprising as the outermost layer of the film was expected to sublime first, whereupon ventilation and temperature would be the main factors influencing the rate. Since both sample groups were stored and measured under identical conditions, the sublimation rate was expected to be identical until the point where the CDD only remained embedded in the paper. It had been hypothesized that

CDD would sublime more slowly from the warmed samples as visual examination showed it penetrated further into the paper. Surprisingly, this proved not to be the case.

The standard deviations were similar for both the warmed and unwarmed samples (fig. 22).

Again, RH is probably the greatest contributing factor in the relatively large SD values. Although the mean RH was a moderate 50%, the difference between the minimum and maximum RH values was as great as 26% with changes ranging from 4% to 18% per day (appendix 2).

As shown in table 10, the two sample groups exhibited nearly identical percent mass losses.

This finding is useful, as studies have shown that water-sensitive media is more successfully protected with the application of molten CDD to both sides of a warmed substrate. According to the results of this test, pre-warming paper-based objects is unlikely to result in slower sublimation times. This information could be helpful for treatment planning; however, if an object can be safely warmed during treatment, similarly elevated temperatures might be used to promote sublimation.

Fig. 21: Mean sublimation rates of CDD, applied as a melt to warmed and unwarmed Whatman filter paper samples, plotted as a function of total mass loss against time. Each data point represents the average of 20 measurements.

0.1200

0.1000

0.0800

0.0600

0.0400

Unwarmed Whatman Filter Paper 0.0200 Warmed Whatman Filter Paper Total Mass Loss of Mass Loss Total (g) CDD and Paper 0.0000 0 24 48 72 96 120 144 168 Time (hr)

Fig. 22: Mean sublimation rates of CDD, applied as a melt to warmed and unwarmed Whatman filter paper samples, plotted as a function of total mass against time with error bars showing standard deviations for the average of 20 measurements

0.3600

0.3400 Unwarmed Whatman Filter Paper

Warmed Whatman Filter Paper 0.3200

0.3000

0.2800

0.2600

0.2400 Ttoal Mass Ttoal of (g) CDD and Paper

0.2200

0.2000 0 24 48 72 96 120 144 168 Time (hr)

TABLE 10: AVERAGE PERCENT MASS LOSS OF CDD OVER TIME FROM WHATMAN FILTER PAPER TREATED WITH MOLTEN CDD TO UNWARMED AND WARMED SUBSTRATES. AVERAGE INITIAL CDD MASSES ARE GIVEN ALONG WITH THE STANDARD DEVIATIONS. ALL AVERAGES WERE CALCULATED FROM 20 REPLICATES PER SAMPLE TYPE.

Unwarmed Warmed Days Average Percent Mass Loss of CDD 1 39.9% 34.5% 2 69.2% 67.1% 3 90.5% 89.0% 4 100.3% 99.2% 5 101.4% 101.0% 6 101.5% 101.2% Average Initial CDD Mass (g) M 0.1065 0.1063 SD 0.004 0.003 SE 0.0008 0.0006

The mean sublimation rates of CDD, applied as a melt and as a saturated solution in petroleum ether (30°C-40°C), from Fabriano Artistico rough finish paper are shown in figure 23.

The initial steepness of the trend line for the solution-treated samples reflects the solvent evaporation. After 24 hours, the two sample groups exhibited similar losses in mass; however, the samples treated with molten CDD displayed residues a full day after all traces disappeared from the samples treated with the saturated solution. This persistence is probably due to the more uneven film layer produced from the molten CDD rather than the 0.02 mm difference in thickness (table 6).

The standard deviations for the two sample groups are similar following the evaporation of the petroleum ether (fig. 24). Fluctuations in RH during this test period were moderate (<1% to 4%) so probably contribute minimally to the SD values.

The percent mass loss results presented in table 11 and the aforementioned visual observations, show that the samples treated with the CDD-saturated solution in low boiling petroleum ether sublimed ~24 hours faster than the papers treated with molten CDD. The

difference in the mass applied — 0.0503 g for the molten-treated samples and 0.0485 g for solution- treated samples — would probably not account for the slower rate. It seems more likely that the slower sublimation of the molten CDD would be caused by the smaller and denser crystal structure.

Fig. 23: Mean sublimation rates of CDD, applied as a melt and as a saturated solution in petroleum ether (30°C-40°C), from Fabriano Artistico rough finish paper with data plotted as a function of total mass loss against time. Each data point represents the average of 20 measurements.

0.1200

0.1000

0.0800

0.0600

0.0400 Total Mass Loss of Mass Loss Total (g) CDD and Paper

0.0200 Molten CDD CDD-Saturated Solution

0.0000 0 24 48 72 96 120 Time (hr)

Fig. 24: Mean sublimation rates of CDD, applied as a melt and as a saturated solution in petroleum ether (30°C-40°C), from Fabriano Artistico rough finish paper with data plotted as a function of total mass against time and error bars showing standard deviations for the average of 20 measurements

0.6400

0.6200 Molten CDD

0.6000 CDD-Saturated Solution

0.5800

0.5600

0.5400

0.5200 Ttoal Mass Ttoal of (g) CDD and Paper 0.5000

0.4800 0 24 48 72 96 120 Time (hr)

TABLE 11: AVERAGE PERCENT MASS LOSS OF CDD, APPLIED AS A MELT AND AS A SATURATED SOLUTION IN PETROLEUM ETHER (30°C-40°C), FROM FABRIANO ARTISTICO ROUGH FINISH PAPER. AVERAGE INITIAL CDD MASSES ARE GIVEN ALONG WITH THE STANDARD DEVIATIONS. ALL AVERAGES WERE CALCULATED FROM 20 REPLICATES PER SAMPLE TYPE.

Molten Solution Days Average Percent Mass Loss of CDD 1 59.1% 59.9% 2 88.9% 95.3% 3 96.3% 99.2% 4 97.5% − Initial CDD Mass (g) M 0.0503 0.0485 SD 0.002 0.009 SE 0.009 0.002

4.2 GC-FID Analyses

The GC-FID results of select samples are given in table 12. As outlined in section 3.3, the samples were drawn from three of the gravimetric tests: (1) waterleaf and gelatin-sized flax papers treated with molten CDD, (2) warmed and unwarmed Whatman filter paper treated with molten

CDD, and (3) Fabriano Artistico rough finish paper treated with molten CDD and a CDD-saturated solution in low boiling petroleum ether. Two replicates from each sample group were analyzed after gravimetric measurements and visual examination indicated that complete sublimation had occurred.

At the time of the hexane extractions, the samples displayed no CDD and had recovered 99.6%-

100% of their original weight.

The retention time of CDD was determined from chromatograms of standard solutions prepared in 400-ppm, 40-ppm, and 4-ppm concentrations of CDD in 10 mL of hexane. The retention times varied slightly between the three runs (16.3 min., 16.9 min., and 17.1 min.) due possibly to fluctuations in the flow rate of the mobile phase or nominally shorter column lengths. As each run contained at least one standard, the correct retention time was easily identified regardless of these variations.

No CDD was detected in 4 out of the 12 samples and extremely small quantities were detected in eight. Quantitative determinations were carried out with calibration curves (one for each

GC unit) plotting the concentration of the standard solutions as a function of peak area (appendices

2 and 3). Auto-injection of the solutions was expected to limit volume errors to <2% (Skoog et al.

2007). The estimated percent recovery was calculated from the known concentration and peak areas of CDD-spiked controls and the mean calibration factors (appendices 3-6). The recovery rates for 8 of the 12 samples were 115% and 120%, thus falling well within acceptable limits; however, the recovery rates for the remaining four samples (waterleaf and gelatin-sized flax samples) were as low as 63% and 31%. These low recovery rates could be due to delays between the application of the

CDD and the hexane extraction, allowing more time for the CDD to sublime and reducing the anticipated mass recovery. If this were the case, the extractions performed on the samples would not necessarily have as low of a recovery rate as the spiked samples. Since the true reason for the low rates is unknown, however, the amount of CDD that was embedded in the waterleaf and gelatin- sized samples at the time of extraction might be higher than the amount detected by GC-FID.

Of the 8 samples from which CDD was detected, 7 contained between <1 µg – 9 µg while

53 µg was detected on a single sample. The sample that retained the most CDD was Whatman filter paper warmed before treatment with molten CDD; however, <1 µg was detected on its replicate.

Because the sample population was so small it is not possible to conclude that prewarming of the substrate causes greater retention of CDD although these few results suggest it may. Nevertheless, the retention of 53 µg of CDD represents a mere 0.05% of the total amount applied to the sample.

For the other samples from which CDD was detected, the residues represented less than 0.01% of the initial application. No traces of CDD were detected on the samples of Whatman filter paper or the Fabriano Artistico rough paper treated with molten CDD; these are both cotton fiber papers, the first unsized and the second synthetically sized.

These results show that gravimetric analysis and visual examination were successful methods for tracking the sublimation of the CDD. Forty-eight hours after the samples returned to their original weight and forty hours after CDD was no longer visible, 99.95%-100% of the CDD had completely sublimed. These findings indicate that CDD does sublime completely from paper if given sufficient time. Because CDD contains no functional groups with which to bond to the paper it is reasonable to assume that only more time is required until it completely sublimes.

TABLE 12: GC-FID RESULTS OF SELECT CDD-TREATED PAPER SAMPLES POST-SUBLIMATION

After After Fiber Sizing Finish Estimated Estimated Detectable Days Days Applied (g) Applied (g) Applied CDD Mass Mass CDD Application Mass of CDD CDD of Mass CDD of Mass Recovery Rate Recovery Mass Regained Mass Regained Mass m)µ ( Recovered Percent of Initial Initial of Percent Warmed Substrate Warmed Hours Since Initial Initial Since Hours Paper Manufacturer Paper Application Method Application Hours Since Visually Visually Since Hours Retention Time (min) Time Retention

flax − rough molten no 0.1 6 40 16 100 0.1 16.9 9 63% Cave Paper flax − rough molten no 0.1 6 16 16 100 0.1 16.9 9 63% Cave Paper flax gelatin rough molten no 0.1 6 38 14 100 0.1 16.9 3 31% Cave Paper flax gelatin rough molten no 0.1 6 38 14 100 0.1 16.9 3 31% Cave Paper cotton − smooth molten no 0.1 6 23 47 100 0.1 − − 120% Whatman cotton − smooth molten no 0.1 6 17 41 100 0.1 − − 120% Whatman cotton − smooth molten yes 0.1 6 23 45 100 0.1 17.1 0.2 120% Whatman cotton − smooth molten yes 0.1 6 21 18 100 0.1 17.1 53 120% Whatman cotton synthetic rough solution no 0.05 4 24 − 99.6 0.05 16.3 4 115% Fabriano cotton synthetic rough solution no 0.05 4 16 − 99.8 0.05 16.3 5 115% Fabriano cotton synthetic rough molten no 0.05 4 16 − 99.6 0.05 − − 115% Fabriano cotton synthetic rough molten no 0.05 4 16 − 99.7 0.05 − − 115% Fabriano

4.3 Water Absorbency Test Analyses

The results of the water absorbency tests are given in tables 13-15. Each table contains the data sets for a given test group, their means (M), standard deviations (SD), and standard errors (SE).

The variability of the results is presented as boxplots in figures 25-28. Hypothesis testing was carried out using two-tailed t-tests with two-sample equal variance to determine whether the water absorption differences between the controls and samples were statistically significant or simply due to random chance. The null hypothesis assumed no statistical difference in the water absorption capacities of the untreated controls and the samples from which the CDD had sublimed. A p-value of <0.05 was considered the threshold of significance.

Table 13 presents the results of the tests performed on the Whatman filter paper controls

(n=15) and samples treated with molten CDD (n=30). One-half of the samples were treated at room temperature and the other half were warmed to ~40ºC before the CDD was applied.

Approximately 20 to 40 hours after the samples returned to their original weight and exhibited no waxy deposits, they were preconditioned, along with the controls, at 23ºC and 13% RH for 48 hours.

Testing therefore took place approximately three days after gravimetric analysis and visual examination indicated that the CDD had completely sublimed. These conditions for assessing complete sublimation were maintained for all subsequent tests. The boxplot in figure 25 shows the distribution of time required in seconds (s) for 0.05 mL of water to be absorbed by the samples and the controls.

The t-test comparing the water absorption rates of the unwarmed samples to the controls indicated a statistically significant difference at the 0.05 level whereas the t-test comparing the warmed samples to the controls showed an even greater statistically significant difference at the 0.01 level. Therefore, the probability that the differences in water absorption between the samples and controls were due purely to random chance is low. It is tempting to correlate the 0.01 and 0.05

significance levels of the warmed and unwarmed samples, respectively, to the varying amounts of

CDD detected by GC-FID analysis i.e., <1 ppm v. 53 ppm, respectively. No significant difference was found, however, between the water absorbency rates of these two sample groups (p=>0.05).

This finding highlights the problem of interpreting results from small sample populations.

Regardless, it seems unlikely that CDD residues on the order of micrograms would appreciably affect the water absorbency of the papers. In any case, the difference in the mean absorption times of the samples and the controls was so small (29 s v. 25 s, respectively) that its practical significance is unimportant (table 13 and fig. 25). Overall, these findings suggest that the application of molten

CDD to slightly warmed unsized, cotton fiber paper caused negligible changes to its water absorbency capacity.

TABLE 13: WATER ABSORBENCY OF WHATMAN FILTER PAPER CONTROL AND WARMED AND UNWARMED SAMPLES POST-SUBLIMATION OF MOLTEN CYCLODODECANE

Untreated Unwarmed Warmed Controls Samples Samples # Time (s) 1 35 27 28 2 27 28 22 3 28 24 32 4 25 27 30 5 20 28 29 6 19 36 28 7 23 35 32 8 25 31 30 9 26 30 32 10 30 27 22 11 24 21 34 12 30 32 25 13 20 28 29 14 21 29 34 15 16 27 34 M 25 29 29 SD 5 4 4 SE 1 1 1

Fig. 25: Boxplot of time required for 0.05 mL of water to be absorbed by Whatman filter paper controls (n=15) and samples post-sublimation of molten CDD from warmed (n=15) and unwarmed (n=15) substrates.

Warmed Samples

Unwarmed Samples

Controls

0 5 10 15 20 25 30 35 40

Time (s)

Table 14 presents the results for the water absorbency tests performed on waterleaf flax papers (n=15) and gelatin-sized flax papers (n=15) treated with molten CDD. As in the previous test set, the samples were preconditioned for 48 hours at 21ºC and 13% RH and then conditioned at

22ºC and 55% RH until equilibrating with the test room conditions.

The t-test comparing the waterleaf flax samples to the controls resulted in p-values >0.05 as did the t-test comparing the gelatin-sized flax samples to the controls. Thus the probability that water absorption differences between the samples and controls are due completely to chance is high.

It can therefore be concluded that the application of the molten CDD to both the waterleaf and sized flax papers did not alter their water absorbency characteristics.

The boxplot in figure 26 shows variability of the length of time required for 0.1 mL of water to be absorbed by the waterleaf flax samples and controls. The variability of this data was more

moderate than that of the data collected for the gelatin-sized flax samples and controls shown in figure 27. This variability is due partially to experimental error. Weighing the mass of water absorbed by the sized samples according to the experimental procedures outlined in TAPPI test T441 proved more difficult to execute due to the rapid evaporation of the water.

TABLE 14: POST-SUBLIMATION WATER ABSORBENCY OF WATERLEAF AND GELATIN-SIZED FLAX PAPER TREATED WITH MOLTEN CYCLODODECANE

Waterleaf Gelatin-Sized Controls Samples Controls Samples # Time (s) Water Mass (g) 1 21 23 0.00677 0.00533 2 21 20 0.00840 0.00684 3 21 22 0.00700 0.00661 4 23 25 0.00639 0.00973 5 25 33 0.00699 0.00782 6 32 29 0.00875 0.00702 7 28 18 0.00791 0.00723 8 32 25 0.00614 0.00700 9 30 26 0.00831 0.01921 10 18 25 0.00712 0.00696 11 20 26 0.00689 0.00737 12 18 20 0.01086 0.00666 13 22 22 0.00620 0.00847 14 25 20 0.00741 0.00781 15 23 21 0.00677 0.00768 M 24 24 0.007 0.008 SD 5 4 0.001 0.003 SE 1 1.0 0.0003 0.0008

Fig. 26: Boxplot of time required for 0.1 mL of water to be absorbed by waterleaf flax paper controls (n=15) and samples post-sublimation of molten CDD (n=15)

Waterleaf Samples

Waterleaf Controls

0 5 10 15 20 25 30 35 40 Time (s)

Fig. 27: Boxplot of water mass absorbed in two minutes by gelatin-sized controls (n=15) and samples post-sublimation of molten CDD (n=15)

Gelatin-Sized Samples

Gelatin-Sized Controls

0.00000 0.00500 0.01000 0.01500 0.02000 Mass of Water (g)

Table 15 presents the results for the water absorbency tests carried out on Fabriano Artistico rough finish paper treated with molten CDD (n=15) and a CDD-saturated solution prepared in low boiling petroleum ether (n=15) as well as untreated controls (n=15). All samples were tested following complete sublimation of the CDD. As in the previously described test sets, the samples were preconditioned for 48 hours at 20ºC and 13% RH and then conditioned at 22ºC and 60% RH until coming into equilibrium with the test room environment.

The t-test comparing the mass of water absorbed in two minutes by the controls and the samples from which the molten CDD had sublimed showed no statistically significant difference

(p=>0.05). Indeed, the mean absorption was identical (table 15 and fig. 28). The opposite result

(p=<0.05) was obtained in the t-test comparing the absorbency of the controls and the samples from which the CDD-saturated solution had sublimed; however, the practical significance seems unimportant as the mean absorptions of the controls and samples were 0.004 g and 0.005 g, respectively. A t-test comparing the absorbency results for the two types of samples showed no statistically significant difference (p=>0.05).

The boxplot in figure 28 shows the variability in the water mass absorbed by the two sample groups and the controls. Unlike the previous boxplot illustrating data variability (fig. 27), there were less extreme variations in this test.

Overall, these tests showed negligible or no changes to the water absorbency of the select samples post-sublimation of CDD. This comports with the GC-FID results, which detected nominal residues in the samples ~48 hours after the samples returned to their original weight or displayed no CDD residues.

TABLE 15: POST-SUBLIMATION WATER ABSORBENCY OF FABRIANO ARTISTICO ROUGH FINISH PAPER TREATED WITH MOLTEN CDD AND CDD-SATURATED SOLUTION IN PETROLEUM ETHER (30ºC -40ºC) AND CONTROLS

Untreated Molten Saturated Controls CDD Solution # Water Mass (g) 1 0.00245 0.00382 0.00442 2 0.00308 0.00337 0.00510 3 0.00409 0.00430 0.00532 4 0.00380 0.00461 0.00559 5 0.00431 0.00565 0.00554 6 0.00466 0.00487 0.00485 7 0.00444 0.00331 0.00412 8 0.00346 0.00619 0.00536 9 0.00268 0.00439 0.00438 10 0.00395 0.00497 0.00464 11 0.00522 0.00318 0.00388 12 0.00298 0.00567 0.00347 13 0.00449 0.00398 0.00334 14 0.00386 0.00335 0.00487 15 0.00331 0.00370 0.00452 M 0.004 0.004 0.005 SD 0.0008 0.001 0.0007 SE 0.0002 0.0003 0.0002

Fig. 28: Boxplot of water mass absorbed in two minutes by Fabriano Artistico rough controls (n=15) and samples post-sublimation of molten CDD (n=15) and CDD-saturated solution in petroleum ether (30ºC-40ºC) (n=15)

Solution Application

Molten Application

Controls

0 0.002 0.004 0.006 0.008

Mass of Water (g)

CHAPTER 5

CONCLUSIONS

Gravimetric analysis indicated that the three inherent paper characteristics examined in this study — fiber type, finish, and the presence of sizing — have negligible effect on the rate of CDD sublimation when applied in the molten state. Moreover, the results also suggested that paper thickness plays an inconsequential role as well. Conceivably, paper thickness could influence the rate if treated with a CDD-saturated solution in high boiling solvent. In such a case, the CDD would penetrate further into the substrate, requiring more time to sublime. Another test would have to be conducted to confirm the validity of this assumption. Although it is rather self-evident, the thickness of the CDD film does influence the rate. Gravimetric analysis also showed that warming the paper samples slowed the rate; however, this delay in sublimation unexpectedly occurred within the first 48 hours after application. As temperature and air circulation were presumed to be the main influences on sublimation at this point and all samples were stored under identical conditions, it is unclear why the warmed samples lost less CDD at the beginning of the test period. The hypothesis that warming the substrate would delay sublimation due to greater penetration appears to be incorrect. Finally, gravimetric analysis of the samples treated with molten CDD and a CDD-saturated solution in low boiling petroleum ether suggested that the solution sublimes faster although the difference in this case was only one day. Overall the results suggest that the sublimation rate of CDD is not affected or minimally affected by all of the paper characteristics and application methods examined in this study. Although these results are not dramatic, it is useful to know that the parameter which cannot be controlled i.e., the composition of the object, does not substantively impact the rate. The thickness of the CDD and its mass over a given surface area, as well as temperature and ventilation, appear to be the main influencing factors in the sublimation rate.

These results also suggest that the molten CDD did not penetrate the paper very deeply.

Cryogenic-SEM imaging of the cross-sections of the samples would have been useful in answering this question as well as the providing visual documentation about the crystal formation of CDD below the surface of the paper.

GC-FID analysis suggests that CDD does fully sublime from paper if given sufficient time.

No CDD was detected on 4 out of the 12 samples tested. Of those samples from which CDD residues were detected, all but one was exceedingly small (<9 µm). The sample from which the most

CDD was detected (53 µg) had been prewarmed before the application of molten CDD; however,

<1 µg had been detected on its replicate. Because the sample size was so small (n=2), it is difficult to conclude with certainty that prewarming the substrate slows the rate of sublimation, although the results of both gravimetric and GC-FID analyses suggest this may be the case. This is intuitive as visual examination shows that CDD is driven further into warmed paper.

Overall, the GC-FID and gravimetric tests were successful methods for tracking the sublimation of CDD. The GC-FID results suggest that all or most of the CDD sublimes within several days of its disappearance from the paper surface regardless of whether it is delivered as a melt or as a saturated solution in low boiling solvent. This indicates that potentially harmful off- gassing ceases to occur relatively soon after visual examination indicates it is gone. Thus, to avoid inhaling CDD vapors it would be prudent to leave treated paper objects in the fume hood at least one week after all visible CDD is gone.

The practical significance of the water absorbency tests is debatable. Although the t-tests showed statistically significant differences between the water absorption capacities of the warmed and unwarmed Whatman filter papers and the controls, the mean absorption rates varied by only 4 seconds, which is unlikely to have any practical impact. Moreover, the minute residues detected by the GC-FID would be unlikely to cause a substantive change in absorption. A statistically

significance difference was also obtained from a t-test comparing the samples treated with CDD- saturated solution and the controls, but again the practical significance is probably inconsequential; the difference in the water mass absorbed by the samples and controls was a mere 1 mg. Overall, these tests showed negligible changes or no changes to the water absorbency of the select samples following sublimation of the CDD. This comports with the GC-FID results, which detected nominal residues in the samples ~48 hours after the samples returned to their original weight or displayed no CDD residues.

In summary, the results of this research showed the sublimation rate of CDD was not affected by any of the paper properties examined in this study: fiber type, finish type, and the presence of sizing. The sublimation rate was affected, however, by the delivery method with warmed substrates slowing the rate of sublimation and a more rapid sublimation occurring with the CDD- saturated solution.

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TAPPI. 2008. Standard conditioning and testing atmospheres for paper, board, handsheets, and related products, T402 sp-08. Atlanta: Technical Association of the Pulp and Paper Industry.

TAPPI. 2009. Water absorptiveness of sized (non-bibulous) paper, paperboard, and corrugated fiberboard (Cobb test), T441 om-09. Atlanta: Technical Association of the Pulp and Paper Industry.

Vernez, D., B. Wognin, C. Tomicic, G. Plateel, N. Charrière, and S. Bruhin. 2011. Cyclododecane exposure in the field of conservation and restoration of art objects. International Archives of Occupational and Environmental Health 84: 371-74.

APPENDIX 1

MATERIALS AND SUPPLIERS Cave Paper Inc. 212 N. 2nd Street Minneapolis, MN 55401 United States • Handmade waterleaf and gelatin-sized 100% flax paper

Fisher Scientific 112 Colonnade Road Ottawa, ON K2E 7L6 Canada • Hexanes H303-3

Japanese Paper Place 77 Brock Avenue Toronto, ON M6K 2L3 Canada • Inoue Haini kozo fiber paper

Kremer Pigments Inc. 247 West 29th Street New York, NY 10001 United States • Cyclododecane

Sigma-Aldrich Canada Co. 2149 Winston Park Drive Oakville, ON L6H 6J8 Canada • Petroleum ether (boiling point range 30°C -40° C)

TALAS 330 Morgan Avenue Brooklyn, NY 11211 United States • Artistico 100% cotton mouldmade paper (rough, cold pressed, and hot pressed)

The Ukrainian Gift Shop Inc. 2782 Fairview Avenue North Roseville, MN 55113 United States • Electric kistka

APPENDIX 2

SUMMARY OF TEMPERATURE AND RELATIVE HUMIDITY DURING GRAVIMETRIC TESTS

TEMPERATURE RH

Gravimetric Test 1: Fiber Type (224 logs) Maximum 22.4°C 36.9% Minimum 20.5°C 24.2% M 21.1°C 32.3% SD 0.4 2.4

Gravimetric Test 2: Waterleaf v. Gelatin Sizing (144 logs) Maximum 21.6°C 65.5% Minimum 19.3°C 42.7% M 20.4°C 57.6% SD 0.6 5.1

Gravimetric Test 3: Finish Type (132 logs) Maximum 22.2°C 62.4% Minimum 20.9°C 36.9% M 21.5°C 50.4% SD 0.3 8.5

Gravimetric Test 4: Warming of Substrate (149 logs) Maximum 22.4°C 62.9% Minimum 20.8°C 36.7% M 21.6°C 49.5% SD 0.3 9.1

Gravimetric Test 5: Melt v. Saturated Solution (117 logs) Maximum 22.1°C 67.9% Minimum 19.2°C 62.4% M 20.3°C 65.1% SD 0.6 1.2 Note: The logging interval for all tests was one hour

APPENDIX 3

DEPENDENCE OF PAPER MASS ON RH: GRAPHS OF CONTROLS

Each data point represents a single measurement taken from one representative control.

Cotton Fiber Control 0.2130 45

0.2125 40

0.2120 35

0.2115 30

Mass (g) (g) Mass 0.2110 25 Temperature & RH & RH Temperature 0.2105 20

0.2100 15 0 2 4 6 8 10 12 Days

Cotton (Whatman) Control (g) Temperature °C % RH

Flax Fiber Control

0.3130 45

0.3125 40

0.3120 35

0.3115 30 Mass (g) (g) Mass 0.3110 25 Temperature & RH & RH Temperature 0.3105 20

0.3100 15 0 2 4 6 8 10 12 Days

Flax (Waterleaf) Control (g) Temperature °C % RH

Kozo Fiber Control

0.0895 45

40 0.0890

35 0.0885 30

Mass (g) (g) Mass 0.0880 25 Temperature & RH Temperature 0.0875 20

0.0870 15 0 1 2 3 4 5 6 7 8 9 Days

Kozo Control (g) Temperature °C % RH

Groundwood Fiber Control

0.1240 45

0.1235 40 0.1230 35 0.1225

0.1220 30

Mass (g) (g) Mass 0.1215 25

0.1210 & RH Temperature 20 0.1205

0.1200 15 0 2 4 6 8 10 12 Days

Groundwood Control (g) Temperature °C % RH

Waterleaf Flax Control

0.391 63 0.390 58 53 0.389 48 0.388 43 38 Mass (g) (g) Mass 0.387 33

28 & RH Temperature 0.386 23 0.385 18 0 1 2 3 4 5 6 7 8 9 Days

Waterleaf Control (g) TEMP °C % RH

Gelatin-Sized Flax Control

0.4090 63 0.4080 58 0.4070 53 48 0.4060 43 0.4050 38 Mass (g) (g) Mass

0.4040 33 28 & RH Temperature 0.4030 23 0.4020 18 0 1 2 3 4 5 6 7 8 9 Days

Gelatin-Sized Control (g) TEMP °C % RH

Fabriano Artistico Cold Pressed Control

65 0.5190 60 0.5170 55 50 0.5150 45 0.5130 40 Mass (g) (g) Mass 0.5110 35

30 & RH Temperature 0.5090 25 0.5070 20 0 1 2 3 4 5 6 7 8 9 10 Days

Cold Pressed Control (g) TEMP (°C) % RH

Fabriano Artistico Hot Pressed Control

0.5250 65 0.5240 60 0.5230 55 0.5220 50 0.5210 45 0.5200 40 Mass (g) (g) Mass 0.5190 35

0.5180 30 & RH Temperature 0.5170 25 0.5160 20 0 1 2 3 4 5 6 7 8 9 10 Days

Hot Pressed Control (g) Temperature (°C) % RH

Fabriano Artistico Rough Control

0.5200 65 60 0.5150 55 50 0.5100 45 40

Mass (g) (g) Mass 0.5050 35

0.5000 30 & RH Temperature 25 0.4950 20 0 1 2 3 4 5 6 7 8 9 10 Days

Rough Control (g) TEMP (°C) % RH

APPENDIX 4

CALIBRATION CURVES AND GC-FID RESULTS FOR CYCLODODECANE PURITY CHARACTERIZATION

Instrument: Agilent 6890 gas chromatograph-flame ionization detector Determined the factors of 400 ppm, 40 ppm, and 4 ppm standard solutions of CDD in hexane. Concentration/Peak Area = Factor

400 ppm / 8213.19 = 0.048702149 Retention time 16.458 min 40 ppm /803.14 = 0.049804517 Retention time 16.381 min 4 ppm / 85.40 = 0.046838407 Retention time 16.361 min

Factor Average: 0.048448358

Agilent GC-FID Linearity for CDD 9000 8000 7000 6000 5000 4000

Area Count 3000 2000 y = 20.549x - 7.2739 R² = 0.99999 1000 0 0 50 100 150 200 250 300 350 400 450

ppm

APPENDIX 5

GC-FID RESULTS FOR WARMED AND UNWARMED WHATMAN FILTER PAPER SAMPLES TREATED WITH MOLTEN CYCLODODECANE

Instrument: Hewlett-Packard (HP) 5890 Series II gas chromatograph-flame ionization detector Determined the factors for 400 ppm, 40 ppm, and 4 ppm standard solutions of CDD in hexane. Concentration/Peak Area = Factor 400 ppm / 3365323 = 0.000118859 40 ppm / 339431 = 0.000117844 4 ppm / 33655 = 0.000118853

Factor Average = 0.000118

Hewlett-Packard GC-FID Linearity for CDD

4000000 3500000 3000000 2500000 2000000 Area Count 1500000 y = 8410x + 1450.3 1000000 R² = 1 500000 0 0 100 200 300 400 500 ppm

CDD-SPIKED CONTROL Determined the GC-FID recovery rate of CDD using a spiked control. Controls were extracted in 10-mL hexane immediately after weighing, but a reduced mass was expected due to sublimation. Whatman filter paper #1: 0.2265 g Whatman filter paper #1 and CDD: 0.2274 g CDD: 0.0009 g = 900 µg = GC-FID target

Multiplied the average factor by the peak area of the CDD to arrive at the amount of CDD in ppm detected by the GC-FID. The retention time of CDD is approximately 17 minutes. (Factor) (Peak Area) = ppm (0.000118) (922150) = 108 ppm detected by GC-FID

Multiplied result by 10 to determine amount of CDD extracted from the control with 10 mL hexane.

(108) (10) = 1080 µg of CDD on the control

Calculated the recovery rate of CDD from spiked control. 1080 µg / 900 µg x 100% = 120%

UNWARMED SAMPLE #1 No visible CDD ~23 hours before hexane extraction. Paper had returned to its initial mass ~47 hours before extraction. No peak at ~17 minutes indicating an absence of CDD.

UNWARMED SAMPLE # 2 No visible CDD ~17 hours before hexane extraction. Paper had recovered its initial mass ~41 hours before extraction. No peak at ~17 minutes indicating an absence of CDD.

WARMED SAMPLE #1 No visible CDD ~23 hours before hexane extraction. Paper had recovered its initial mass ~45 hours before extraction. Retention time: 17.063 Peak area: 180 (0.000118) (180) = 0.02 ppm detected by GC-FID (0.02) (10) = 0.2 µg of CDD on sample

WARMED SAMPLE #2 No visible CDD at the time of hexane extraction. CDD had been visible ~21 hours prior to extraction. Paper had recovered its initial mass ~18 hours before extraction. Retention time: 17.061 Peak area: 44669 (0.000118) (44669) = 5.3 ppm detected by GC-FID (5.3) (10) = 53 µg of CDD on sample

APPENDIX 6 GC-FID RESULTS FOR WATERLEAF AND GELATIN-SIZED FLAX PAPER SAMPLES TREATED WITH MOLTEN CYCLODODECANE

Instrument: Hewlett-Packard (HP) 5890 Series II gas chromatograph-flame ionization detector Determined the factor for a 400-ppm standard solution of CDD in hexane. The linearity of 400 ppm, 40 ppm, and 4 ppm standards had been demonstrate on the warmed and unwarmed Whatman filter paper samples treated with molten CDD on the HP 5890 Series II GC-FID (see Appendix 5). Concentration /Peak Area = Factor 400 ppm / 3480961 = 0.000114911

Determined the GC-FID recovery rate of CDD using spiked controls. Controls were extracted in 10-mL hexane immediately after weighting, but a reduced mass was expected due to sublimation. CDD-SPIKED CONTROL WATERLEAF FLAX PAPER Waterleaf flax paper: 0.3341 g Waterleaf flax paper and CDD: 0.3351 g CDD: 0.0010 g = 1000 µg = GC-FID target

Multiplied result by 10 to determine amount of CDD extracted from the control with 10 mL hexane.

(62.5) (10) = 625 µg of CDD on the waterleaf control Calculated the recovery rate of CDD from spiked control. 625 µg /1000 µg x 100 = 63%

CDD-SPIKED CONTROL GELATIN-SIZED FLAX PAPER Gelatin-sized flax paper: 0.3448 g Gelatin-sized flax paper and CDD: 0.3459 g CDD: 0.0011 g = 1100 µg = GC-FID target

(Factor) (Peak Area) = ppm (0.000114911) (295783) = 34 ppm of CDD detected by GC-FID

Multiplied result by 10 to determine amount of CDD extracted from the control with 10 mL hexane.

(34) (10) = 340 µg of CDD on the gelatin-sized control Calculated the recovery rate of CDD from spiked control. 340 µg / 1100 µg x 100 = 31%

WATERLEAF FLAX SAMPLE #1 No visible CDD at the time of hexane extraction. CDD had been visible ~40 hours prior. Paper returned to its initial mass ~16 hours before extraction. Retention time: 16.929 Peak area: 7376 (0.000114911) (7376) = 0.847583536 ppm detected by GC-FID (0.85) (10) = 9 µg of CDD on sample

WATERLEAF FLAX SAMPLE #2 No visible CDD at the time of hexane extraction. CDD had been visible ~16 hours prior. Paper returned to its initial paper mass ~16 hours before extraction. Retention time: 16.930 Peak area: 7502 (0.000114911) (7502) = 0.862062322 ppm detected by GC-FID (0.86) (10) = 9 µg of CDD on sample

GELATIN-SIZED FLAX SAMPLE # 1 No visible CDD at the time of hexane extraction. CDD had been visible ~38 hours prior. Paper returned to its initial mass ~14 hours before extraction. Retention time: 16.927 Peak area: 2796 (0.000114911) (2796) = 0.321291156 ppm detected by GC-FID (0.32) (10) = 3 µg of CDD on sample

GELATIN-SIZED FLAX SAMPLE #2 No visible CDD at the time of hexane extraction. CDD had been visible ~38 hours prior. Paper returned to its initial mass ~14 hours before extraction. Retention time: 16.926 Peak area: 2901 (0.000114911) (2901) = 0.333356811 ppm detected by GC-FID (0.33) (10) = 3 µg of CDD on sample

APPENDIX 7

GC-FID RESULTS FOR ARTISTICO ROUGH PAPER SAMPLES TREATED WITH MOLTEN CYCLODODECANE AND CDD-SATURATED SOLUTIONS

Instrument: Agilent 6890 gas chromatograph-flame ionization detector Determined the factor for a 400-ppm standard solution of CDD in hexane. The linearity of the 400 ppm, 40 ppm, and 4 ppm standards had been demonstrated in the CDD purity characterization on the Agilent 6890 GC-FID (see Appendix 4). Concentration /Peak Area = Factor 400 ppm / 9900 = 0.04040404 Determined the GC-FID recovery rate of CDD using a spiked control. Controls were extracted in 10-mL hexane immediately after weighing, but a reduced mass was expected due to sublimation.

CDD-SPIKED CONTROL (APPLIED AS A MELT ONLY) Artistico rough paper: 0.4863 g Artistico rough paper and CDD: 0.4872 g CDD: 0.0009 g = 900 µg = GC-FID target

Multiplied result by 10 to determine amount of CDD extracted with 10 mL hexane from the control.

(104) (10) = 1040 µg of CDD on the Artistico rough control Calculated the percent of CDD detected by the GC-FID on spiked control. 1040 µg /900 µg x 100 = 115%

CDD-SATURATED SOLUTION ON ARTISTICO ROUGH SAMPLE #1 No visible CDD at the time of hexane extraction. CDD had been visible ~24 hours previously. Paper had recovered 99.6% of its initial mass (total mass of 0.5006 g at the time of extraction; initial paper mass of 0.4986 g). Retention time: 16.323 Peak area: 10.05 (0.04040404) (10.05) = 0.406 ppm detected by GC-FID (0.406) (10) = 4 µg of CDD on sample

CDD-SATURATED SOLUTION ON ARTISTICO ROUGH SAMPLE #2 No visible CDD at the time of hexane extraction. CDD had been visible ~16 hours previously. Paper had recovered 99.8% of its initial mass (total mass of 0.4985 g at the time of extraction; initial paper mass of 0.4973 g). Retention time: 16.325 Peak area: 11.57 (0.04040404) (11.57) = 0.4674 ppm detected by GC-FID (0.4674) (10) = 5 µg of CDD on sample

MOLTEN CDD ON ARTISTICO ROUGH SAMPLE #1 No visible CDD at the time of hexane extraction. CDD had been visible ~16 hours previously. Paper had recovered 99.6% of its initial mass (total mass of 0.4976 g at the time of the extraction; initial paper mass of 0.4955 g). No peak at ~17 minutes indicating an absence of CDD.

MOLTEN CDD ON ARTISTICO ROUGH SAMPLE #2 No visible CDD at the time of hexane extraction. CDD had been visible ~16 hours previously. Paper had recovered 99.7% of its initial mass (total mass of 0.5018 g at the time of extraction; initial paper mass of 0.5001 g). No peak at ~17 minutes indicating an absence of CDD.