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Cahiers François Viète
III-2 | 2017
From Bench to Brand and Back: The Co-Shaping of
Materials and Chemists in the Twentieth Century
Quality Matters for Historical Plastics: The Past-
Making of Cellulose Nitrates for Future
Preservation
La qualité importe pour les plastiques historiques : Analyse du passé des nitrates
de cellulose en vue de leur préservation future.
Anita Quye
Electronic version
URL: https://journals.openedition.org/cahierscfv/799
DOI: 10.4000/cahierscfv.799
ISSN: 2780-9986
Publisher
Nantes Université
Printed version
Date of publication: June 1, 2017
Number of pages: 45-65
ISBN: 978-2-86939-244-3
ISSN: 1297-9112
Electronic reference
Anita Quye, “Quality Matters for Historical Plastics: The Past-Making of Cellulose Nitrates for Future
Preservation”, Cahiers François Viète [Online], III-2|2017, Online since 01 June 2017, connection on 11
October 2024. URL: http://journals.openedition.org/cahierscfv/799 ; DOI: https://doi.org/10.4000/
cahierscfv.799
The text only may be used under licence CC BY-NC-ND 4.0. All other elements (illustrations, imported
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CONTENTS
Introduction – Material Things, Scales and Trans-Operations
Pierre Teissier, Cyrus C. M. Mody, Brigitte Van Tiggelen
Part I – The Plasticity of Things and People
• AUGUSTIN CERVEAUX ................................................................................ 21
Paint as a Material: The Transformation of Paint Chemistry and
Technology in America (ca. 1880-1920)
• ANITA QUYE ............................................................................................... 45
Quality Matters for Historical Plastics: The Past-Making of
Cellulose Nitrates for Future Preservation
Con
Part II – Knowing by Making and Making by Knowing
• PHILIPPE MARTIN ....................................................................................... 69
Twentieth Century Fertilizers in France from Natural Mixing to
Artificial Making (1890-1970)
• APOSTOLOS GERONTAS .............................................................................. 93
Chromatographs as Epistemic Things: Communities around the
Extraction of Material Knowledge
• PIERRE TEISSIER ......................................................................................... 117
The Exotic Glasses of Rennes (France): Local Knowledge-Making
in Global Telecommunication
Part III – Innovating and Recycling: Telling the Stories of Materials
• JENS SOENTGEN ......................................................................................... 155
Making Sense of Chemistry: Synthetic Rubber in German Popular
Scientific Literature (1929-2009)
• SACHA LOEVE ............................................................................................ 183
Point and Line to Plane: The Ontography of Carbon Nanomate-
rials
• CYRUS C. M. MODY .................................................................................... 217
The Diverse Ecology of Electronic Materials
Cahiers François Viète, série III, 2, 2017, p. 45-65
Quality Matters for Historical Plastics:
The Past-Making of Cellulose Nitrates
for Future Preservation
Anita Quye*
Abstract
The material degradation of an historical artifact through chemical breakdown may place the ob-
ject at the end of its useful heritage “life” in terms of aesthetic value and appearance. But all is not
lost in the ephemeral world of historical synthetic plastics. The chemical analyses of degraded cellu-
lose nitrate artifacts have unlocked material clues that not only help explain stability variations to
guide collection care and preservation, but also bring insight into past manufacturing materials,
methods and quality control during production. Translating the industrial materials of a degrading
artifact by understanding its past to inform its future can revive it with a new cultural significance,
and engages heritage scientists, historians and conservators in an innovative community of “com-
plementary science” as defined by Hasok Chang (2004).
Keywords: conservation science, modern plastic materials, cultural value, analytical chemistry, in-
dustrial heritage, history of science, cellulose nitrate, degradation, modern history.
Résumé
La dégradation matérielle d’un artefact historique par décomposition chimique peut amener l’objet
à la fin de sa “vie” patrimoniale utile en termes de valeur esthétique et d’apparence. Néanmoins,
tout n’est pas perdu dans le monde éphémère des plastiques synthétiques historiques. Les recherches
en chimie analytique sur les artefacts en nitrate de cellulose dégradés ont révélé des indices matériels
qui non seulement aident à expliquer les variations de stabilité pour améliorer la conservation
mais engendrent aussi une connaissance accrue dans la fabrication des matériaux, les méthodes et
contrôles de qualité lors de la production initiale. Traduire les matériaux industriels d'un artefact
dégradé en comprenant son passé pour informer son futur peut le relancer dans une nouvelle signifi-
cation culturelle et rassembler les chercheurs en patrimoine, les historiens et les restaurateurs en une
communauté novatrice de “sciences complémentaires” selon la définition d’Hasok Chang (2004).
Mots-clés : science de la conservation, matériaux plastiques modernes, valeur culturelle, analyse
chimique, patrimoine industriel, histoire des sciences, nitrate de cellulose, dégradation, histoire
contemporaine.
* PhD, CChem MRSC. Senior Lecturer in Conservation Science, Centre for Textile
Conservation and Technical Art History, School of Culture and Creative Arts,
University of Glasgow, 8 University Gardens, Glasgow, UK, G12 8QH.
46 ANITA QUYE
he creative science of taking a familiar material and chemically
changing it into new forms is epitomized by the revolution in the
industrial semi-synthesis of plastics from the mid-19th century
onwards. The earliest embodiment was cellulose nitrate, known to many by
its most familiar name Celluloid. Cellulose nitrate was made by chemical
modification of the natural plant polymer, cellulose, and entered commer-
cial production in the 1860s when synthetic organic chemistry and manu-
facturing technology were opening up new worlds of scientific possibilities
for industry.
Historical examples of cellulose nitrate that have survived intact and
in pristine condition to the present day are testimonies to the successful
balance between raw materials, chemical processing and manufacturing
skills. But what can be said of cellulose nitrate when the historical material
degrades, as is happening to a small but nonetheless significant number of
objects in heritage collections worldwide and exemplified by figure 1? Why
are some cellulose nitrate artifacts succumbing to the effects of long-term
aging more readily than others? As importantly, does chemical degradation
mark the end-point of cultural heritage usefulness for such artifacts? These
questions are important for conservation scientists and conservators to an-
swer for the preservation of this landmark historical plastic.
Figure 1 - Two pictures of the same cellulose nitrate spectacle frames, in 2002 in visibly good
condition (left) and in 2014 in a degraded state (right). (Source: Photographs courtesy of Yvonne
Shashoua, National Museum of Denmark)
Degrading cellulose nitrate not only causes its own auto-catalytic de-
struction, but also releases corrosive volatile chemicals that can induce the
breakdown of objects in its vicinity. Conservation research on cellulose ni-
trate degradation has focused mostly on analytical studies of chemical
changes to the modified polymer, loss of its additive plasticizers, and the
accelerating effects of increased temperature and relative humidity on its
T
QUALITY MATTERS FOR HISTORICAL PLASTICS 47
breakdown (Reilly, 1991; Derrick et al., 1993; Feller, 1994). This under-
standing has been invaluable for informed management of storage and dis-
play environments for historical cellulose nitrate plastic collections (The
British Standard Institute, 2012, p. 21), but does not satisfactorily explain
what triggers the seemingly random breakdown of the plastic in the first
place.
In this essay, I will discuss how reconnecting the history of cellulose
nitrate manufacture and the chemistry of past production with present-day
material characteristics and chemical composition unveil a fuller picture
that helps to explain the preservation behavior of this aged plastic. Within
the books and journal articles published between the mid-19th century and
mid-20th century about the making of cellulose nitrate, the technical details
and chemistry of the process are well-described alongside practical issues
that had to be overcome to produce a good-quality material. In these ac-
counts we rediscover the importance of controlling the residual levels of a
chemical in a fundamental stage of synthesis for the plastic. We find that
the issue persisted from the earliest days of cellulose nitrate production un-
til its industrial decline in the 1960s, and that quality affected the stability of
the end-product even within its commercial lifetime. We also see that man-
ufacturers used certain colorants and additives to stabilize the plastic by
counteracting the effect of detrimental residues. Revisiting this information
allows us to appreciate the material complexities of cellulose nitrate plastic
which proved too unpredictable for manufacturers to manage – despite
decades of dedicated research – when faced with competition from new
petrochemical plastics.
By connecting the historical technical literature for the industrial
production of cellulose nitrate plastic with its chemical composition in his-
torical artifacts, we are able to generate a materially-focused body of prima-
ry evidence relating a product’s quality to its long-term stability. Doing this
enables us to re-contextualize the significance of a plastic artifact’s material-
ity as it changes from an un-degraded to degraded state, in terms of its
chemical value rather than its aesthetics or function. Thus the cultural value
of the degraded heritage artifact takes on new meaning as a consequence of
changes in its material composition. Instead of physical degradation mark-
ing the end-point in an artifact’s usefulness to historical understanding, it
becomes a new insight into less tangible aspects of industrial manufacture,
such as the undocumented reasons and decisions made by the manufactur-
ers about acceptable quality using technical and scientific know-how that
we no longer know or appreciate. This raises two important ethical ques-
tions for de-acquisition of degraded historical materials. One is that we un-
dervalue material change as an indicator of past manufacturing practice; if
48 ANITA QUYE
the object is disposed of, the material evidence goes too. The other is that if
the trigger for degradation is inherent in manufacture and in the material
itself, and we do not appreciate that the trigger cannot be controlled or re-
moved, then time, effort and resources are expended in a losing battle of
preservation. Thus, more interdisciplinary dialogue is required among histo-
rians, conservation scientists, and conservators about the significance and
value of such materials in a research context. Studying and evaluating our
modern industrial material culture through this new perspective opens up a
new community in history of science with many possibilities.
In this chapter, I discuss how the chemical challenges faced by cellu-
lose nitrate plastic manufacturers in the past to assure quality control for
their brand product has resulted in inherent properties affecting the preser-
vation chances of the material as heritage artifacts. Addressing first the ap-
parently random behavior of the aged plastic and its consequences for her-
itage collections, I show how documented manufacturing issues involving
residual acids, additives, and the limited control of production variables that
could not be overcome despite advances in chemical understanding, are
linked. They reveal little change in material quality throughout a century of
commercial manufacture. These are taken as material reference points to
explain the chemical differences between degraded and un-degraded histor-
ical plastic examined at the bench of today’s conservators and conservation
scientists in a quest for strategies to preserve the material. The conclusion is
that even if the material cannot be saved it acquires important new value
and significance.
The Loss of Plasticity: From the Aging of Brand Materials to their
Bench Analysis
• Historical Context of an Interdisciplinary Project
As a conservation scientist in a national museum who was surveying
plastic artifacts across collections of decorative arts and technical and social
history in the early 1990s (Quye, 1993), I, like my peers, was perplexed by
the sudden unexpected breakdown of aged cellulose nitrate plastic. Indeed,
most curators and conservators were used to regarding plastics as stable
materials and of relatively little research value. In the 1980s, historical inte-
rest in the 19th century and early 20th century started to grow, and this is
when people were surprised to find that ‘everlasting’ plastics could fall
apart. Analysis of the degraded examples revealed cellulose nitrate to be a
vulnerable plastic, along with cellulose acetate, poly(vinyl chloride), po-
ly(urethanes) and synthetic rubber. When curators, conservators and heri-
QUALITY MATTERS FOR HISTORICAL PLASTICS 49
tage scientists recognized the problem and became more observant, it was
realized that certain plastics could degrade within six months even in good
museum conditions (Keneghan, 2005). Surveys during the early 1990s of
plastic artifacts in the Victoria and Albert Museum and British Museum
revealed that 1% were a “high conservation” priority because they were
actively degrading (Shashoua, 2009, p. 8-9). This number, although small,
has a big impact because the vapors released from degrading cellulose ni-
trate affect not only the materials of the artifact itself but also other mate-
rials nearby. Cellulose nitrate was widely used to imitate relatively stable
natural materials like ivory, mother of pearl and tortoiseshell, so it often
goes unnoticed until a disguised artifacts starts to behave unexpectedly by
breaking down.
Most of these historical objects had entered the museum with an un-
known user life behind them, yet despite a stable and controllable museum
environment, something was causing a few to randomly fall apart even
within sets of related objects manufactured at the same time by the same
maker. In the late 1980s the degradation problems of historical cellulose
nitrate plastic had just been recognized (Green & Bradley, 1988). Some
conferences were organized on the subject, like “Saving the Twentieth Cen-
tury: The Conservation of Modern Materials” held in 1991 in Ottawa
(Grattan, 1993). Analytical studies by conservation scientists worldwide
started reaching similar conclusions – the material was losing its flexibility-
inducing plasticizers and the chemically-modified nitrocellulose polymer
was breaking down (Shashoua & Ward, 1995). Yet these chemical changes
could not explain satisfactorily the hit-or-miss behavior of the material.
Amongst the many chemical complexities of this aged and aging historical
plastic, might we be overlooking a basic inherent common factor linking
the stability of today’s artifacts to past manufacturing processes?
With awareness rising amongst conservators and curators of unstable
cellulose nitrate plastics in the late 1990s (Springate, 1997), the focus of ex-
plaining destabilization remained on the loss of nitrate from the cellulose.
Some researchers suggested residual acids from manufacture as a possible
reason (Selwitz, 1988; Reilly, 1991). Investigating this manufacturing residue
as a cause of random breakdown in old cellulose nitrate required not only
that the materials of the artifacts be studied, but also a better understanding
of quality issues in past production. This would entail a different conserva-
tion science research approach, combining the polymer chemistry of histor-
ical plastics artifacts with original technical manufacturing information, and
co-using primary evidence from the plastic itself and historical industrial
documentation. For this endeavor, I initiated an interdisciplinary collabora-
tion between chemistry and conservation science, which led to the doctoral
50 ANITA QUYE
study by chemist Robert Stewart (1997), jointly funded by the Engineering
and Physical Sciences Research Council and the Scottish Conservation Bu-
reau of Historic Scotland. This interdisciplinary research is the focus of my
discussion.
Manufacturing chemists of the early 20th century talked about stabil-
ity issues of plastics. A critical step for end-product quality was the removal
of trace sulfuric acid and sulfates following the reaction between cellulose
and a nitric acid mixture with sulfuric acid to facilitate the nitration. Inade-
quate washing at this stage resulted in a poor quality plastic. This once-
common knowledge had been lost and forgotten with the demise of the
cellulose nitrate industry in the 1960s (Meikle, 1995, p. 28) and overlooked
by conservation scientists trying to understand the behavior of the histori-
cal material. Rediscovering the impact of residual sulfuric acid helped focus
our attention on inherent manufacturing problems that explained the odd
behavior of the historical plastic. It also transpired that past manufacturers
viewed high levels of residual sulfate content as indicative of a poorly made
product. Thus historical plastic with a detrimental acidic content was pri-
mary material culture evidence of quality control in the earliest of the man-
made plastics. This casts a different light and novel value on degraded plas-
tics in heritage collections, as windows into past industrial processes.
• Bench Making of Cellulose Nitrate
To understand the relevance of production quality and its relation-
ship to the stability of historical cellulose nitrate plastic, we first need to
understand its making. Manufacture operated within material boundaries
imposed by the raw materials, the level of control over the chemical
process, and the skill of the maker. All three had a physical impact on the
material in terms of its mechanical and chemical durability and stability.
This resonated in the shaky start of the first commercial production of cel-
lulose nitrate plastic by Alexander Parkes in London in 1866 under the
name of Parkesine. By 1868 Parkesine production had ceased because of
poor quality resulting from cost-cutting measures to produce too much
plastic with cheap materials (Friedel, 1983, p. 10). Customers complained
that it distorted within a few weeks (Mossman, 1994, p. 15). When John
Wesley Hyatt and his brother Isaac Smith started making their version,
called Celluloid, in 1872 in the United States of America, they used cam-
phor as a plasticizer and ethyl alcohol as the solvent. These were two ingre-
dients that Parkes included in his 1865 patent for Parkesine, but deemed
unnecessary to use himself until working for Daniel Spill in London to
make Spill’s version, called Xylonite, in the early 1870s (Friedel, 1983 p. 10-
12).
QUALITY MATTERS FOR HISTORICAL PLASTICS 51
Celluloid, Xylonite and other commercial brands of cellulose nitrate
were more stable than Parkesine, and went on to commercial success as
simulants of ivory, pearl, coral, jet, marble, tortoiseshell, amber, horn and
onyx as well as in transparent form. The consumer market was favored by
the dependable supply of the plastic compared to the natural materials
(Friedel, 1983, p. 64). Cellulose nitrate plastic was produced in Europe and
in the USA until the 1960s, and made into a wide range of household
goods, decorative items, and industrial parts. The versatility of cellulose ni-
trate in sheet, extruded rod, and molded forms led to a broad and diverse
range of applications over its production lifetime, including Victorian hair
combs, Constructivist art sculptures in the 1920s, parts for planes and cars,
pearlescent casings and finishes for accordions and other musical instru-
ments, ammunition casings, and table tennis balls (Katz, 1985; Meikle,
1995). Additionally, there were cellulose nitrate films, lacquers, explosives,
and, for a short time, fibers. It is little wonder, then, that cellulose nitrate
has made its way into so many public museums, galleries, archives and his-
toric houses, and private collections (Lavédrine et al., 2012).
At its simplest constituent level, cellulose nitrate plastic is a polymer,
which gives physical structure to the material, mixed with a plasticizer,
which imparts flexibility. It was classed as a semi-synthetic because the po-
lymer was made of cellulose from cotton and wood that was chemically
modified by a nitrating acid mixture. Cellulose is composed of long chain
molecules of carbon and hydrogen atoms with many hydroxyl (-OH) side
groups, and it is these hydroxyls that are replaced with nitrate groups by an
esterification reaction involving an aqueous acidic mixture of nitric acid,
water and, importantly, sulfuric acid. With different formulations of the
acid mixture, different degrees of nitration substitution of the cellulose hy-
droxyls were possible. The nitrogen content determined the physical prop-
erties of end-product: 10.5% for moldable plastics; 11.5% for films; and up
to 13.5% for explosives (Boschan et al., 1955; Reilly, 1991).
• Manufacturing Problems
Sulfuric acid played an essential controlling role in the first stage of
the polymer-modification reaction pathway by forming cellulose sulfate
esters, which were then substituted with nitrates. The right strength and
proportion of sulfuric acid in the acid mix was crucial for regulating the
substitution rate and number of nitrate molecules, which impacted on the
nitration content and hence the end-product. Reaction conditions and qual-
ity of the starting materials influenced side-reactions, which also affected
the end-result. The reaction solution was always a complex mix of cellulose,
nitric acid, sulfuric acid, water, cellulose sulfates, cellulose nitrates, sulfonic
52 ANITA QUYE
and nitrosulfonic acid esters, oxycellulose and hydrocellulose (Worden,
1911).
A well-documented stabilizing step was repeated post-reaction wash-
ing of the esterified cellulose to remove unwanted traces of sulfuric acid
and sulfate esters. From the earliest days of Hyatts’ process and throughout
the production decades of cellulose nitrate, this removal of acidic residues
was a critical stage (Friedel, 1983, p. 17). It was alerted to in many publica-
tions, including key works on cellulose esters by the American chemist Ed-
ward Chauncery Worden (1911, p. 595-596), publications by industrial
chemists, like Foster Sproxton (1938), manager of the British Xylonite
Company, and many others well into the 1950s (Miles, 1955). All noted that
the quality of the end plastic depended on effective washing. The reason
was that residual sulfuric acid would attack the structure-giving cellulose
polymer backbone of the plastic, while the sulfate esters could form free
acids, which catalyzed the degradation if not removed. Washing was done
in large heated vats with boiling water until the overall acidity was reduced
to 0.2% sulfate content or less (Worden, 1911). This proved to be a critical
factor for the degradation susceptibility of historical cellulose nitrate.
Unstable cellulose nitrate plastic was always a concern of the manu-
facturers, and deemed a sign of a poor quality product. Problems included
warping and distortion (Meikle, 1995, p. 23), and a yellow or brown color
forming during ‘seasoning’ after processing or upon long storage (Worden,
1911). In the late 1920s, Ellington, a polymer chemist, investigated the
problem with chemical analysis of fourteen transparent cellulose nitrate
sheets manufactured in Germany, France, Britain, America, Switzerland and
Japan which had yellowed and degraded (Ellington, 1929). His study
showed that the two key destabilizing factors were the percentage (%) con-
tent of sulfate and of cellulose sulfate. The stable plastics had less than 0.1%
total sulfate content whereas the unstable ones had 0.80% to 0.99% free
sulfate and 0.24% to 0.63% cellulose sulfate. This chimes well with Ste-
wart’s modern analysis by ion chromatography of degraded historical cellu-
lose nitrate plastic objects with varying visual signs of active degradation,
such as discoloration, cracks, and characteristic square pattern crazing
(Quye & Williamson, 1999, p.122-135; Shashoua, 2009, p. 151-184). The
deteriorated aged plastics studied by Stewart all had a minimum of 0.5%
total sulfate content. This was remarkably close to the 0.2% threshold max-
imum for a good quality plastic advocated by Worden a century earlier, de-
monstrating that manufacturers had the analytical capability and chemical
understanding to measure and monitor the residual acid content of cellu-
lose nitrate from the start of the 20th century, if not earlier. Indeed, they
QUALITY MATTERS FOR HISTORICAL PLASTICS 53
acknowledged the importance of bench chemistry to control the properties
of brand materials.
• Opaque versus Transparent Plastic: A Clear Question of Quality
Besides residual acids in degraded historical cellulose nitrate plastic,
Stewart investigated another significant chemical composition factor linked
to the common observation by conservators and curators - that transparent
forms of the plastic tend to be more degraded than opaque forms. Again
using ion chromatography, he found a high correlation between clear arti-
facts with visible cracks or yellowing and more than 0.5% sulfate content.
However, if the plastic was opaque there were few visual signs of active
degradation even if it was over the critical 0.5% total sulfate threshold. Why
was this? Was there another quality relationship? The answer lay once again
in the manufacturing chemistry for the plastic.
A lucrative consumer market for cellulose nitrate plastic was as a si-
mulant of luxury natural materials. Imitation ivory, jet, pearl, coral and
amber were popular forms (Böckmann, 1880, p. 97-100; Worden, 1911,
p. 687-697), and it is under these guises that the plastic is often present in
heritage collections or fashion, art, technology, social, and even natural his-
tory. To make imitation ivory and other opaque forms, the manufacturers
added zinc oxide, zinc carbonate, or calcium carbonate to the cellulose ni-
trate dough (Sachs & Byron, 1921). Worden commented that “Transparent
plastic is harder to keep stable than translucent and opaque, due to the sta-
bilizing action of the zinc oxide and carbonate and other pigments present
in the latter, and usually in large quantities” (Worden, 1911, p. 595).
Stewart readily detected zinc in historical samples of ‘ivory’ cellulose
nitrate using X-ray fluorescence spectroscopy, and titanium from titanium
dioxide, which was a common opacifier in many industrial applications
from 1916. Stewart’s sulfate analysis of these same artifacts confirmed that
the minerals had maintained a protective effect over the decades in the
plastics with over 0.5% of the detrimental sulfate content because they
showed no sign of degradation. The chemicals added during manufacture
to opacify the plastic were having a stabilizing effect on historical cellulose
nitrate.
Cellulose nitrate manufacturers referred to their stabilizing chemical
additives as antacids. Tellingly, the antacids were a safeguard against resi-
dual sulfuric acid and sulfates, and sometimes added even if deemed unne-
cessary at the time of production. The opacifying inorganic mineral were
also classed as antacids, so their dual role as stabilizers was known. Anta-
cids for transparent plastics were organic compounds, like urea (Worden,
1911). There were differing opinions about whether antacids for transpa-
54 ANITA QUYE
rent cellulose nitrate covered up a poorly-manufactured product. Antacids
were encouraged in a book about European cellulose nitrate production in
the 1910s (Masselon et al., 1912) while a book about the American cellulose
nitrate industry, published at the same time, endorsed thorough washing
and advised against antacids (Worden, 1911). Washing was the industry-
wide preference on both sides of the Atlantic. In Ellington’s research of the
different makes of cellulose nitrate sheet (Ellington, 1929), he classed the
stable plastics with low sulfate content and little urea or mineral content as
high quality, viewing the low sulfate levels as good production control.
Samples with high quantities of sulfate contained appreciable levels of urea
(0.2% to 1.2%), which Ellington deemed “objectionable” to him as a poly-
mer chemist. He referred to the urea as “artificial stabilisation” because
manufacturers would have been aware that the sulfate in their material was
an “undesirable impurity”. Studies of urea in historical cellulose nitrate plas-
tics have not been published yet, but urea content should be investigated to
see if it is detectable and correlates with the stability of the historical plas-
tics.
Herein lies an interesting quality question with implications for the
interpretation of historical collections. If it took better production control
to make a stable transparent cellulose nitrate than it did for an opaque form
because the opacifying minerals acted as antacids, were lower quality plas-
tics used to make the expensive-looking simulants like ivory, pearl, coral
and onyx? If so, the technological value and quality of clear cellulose ni-
trates would be higher than the simulants despite the simulants having
more aesthetic appeal and looking like a better class of material. Of course
not all clear cellulose nitrate plastics were necessarily high quality, as evi-
denced by the many instances of degraded historical drawing instruments
which tend to be transparent, but it does open up a new area for discussion
about intrinsic and implied material value of historical synthetic simulants
of natural materials between historians and curators of design and technol-
ogy.
Chemistry Matters
While Stewart’s analytical study of degraded cellulose nitrate plastic
links long-term stability to residual acids and added opacifiers from manu-
facture, it is only a partial insight into the chemical complexities of the end-
product. Making cellulose nitrate was a multi-stage chemical balancing act.
With the industry spanning from the 1860s to the early 1960s, it covered a
monumental period of increasing chemical understanding as well as tech-
nical and social change. Manufacturing transitioned from an arena of expe-
QUALITY MATTERS FOR HISTORICAL PLASTICS 55
rimentation and trade secrets to targeted research and greatly enhanced
chemical knowledge of the materials and product. Yet the basic chemistry
of the process did not change. What impact did this have on the material
quality? And what are the implications for historical collections? Do the
longevity and stability of old cellulose nitrate plastics correlate with date of
production? To begin finding answers, the role of chemistry in the industry
needs to be examined more closely.
Chemistry was intrinsic throughout the whole process of making cel-
lulose nitrate. From its earliest days, the cellulose nitrate industry acknowl-
edged the necessary input of chemists. Raw materials, solvents and addi-
tives had to be selected, purity-tested and prepared. The nitrating acid
mixture needed specific formulations, while the esterification step required
monitoring and control. Spent acid had to be removed and recycled. The
right type and amount of solvent and plasticizer had to be added to the ni-
trated cellulose to make a ‘colloidon’ of the required viscosity for handling
and shaping. Chemists were employed as in-house analysts and managers to
select the best materials and to control the process. This included solvent
solubility tests for the degree of cellulose nitration, and viscosity measure-
ments to assess physical quality for processing (Schüpphaus, 1915; Partidge,
1929). Hyatt said he was “allowed to employ a chemist [Mr Frank Vander-
poel] for determining our acids and to systemize our nitration, instead of
merely using hydrometers and thermometers” (Hyatt, 1914).
The era between the 1870s and early 1900s was one of empirical ven-
ture for the makers, but driven more by tacit technical experience and
commercial enterprise rather than systematic scientific advances (Friedel,
1983). The molecular structure of cellulose was not deduced by Cross, Be-
van and Beadle until 1895, although as it turned out advancements in po-
lymer and macromolecular theories over the following decades had little
effect on improving the quality of manufactured cellulose nitrate plastic.
The best raw materials and additives were found early on because of indus-
trial trials and observations (Friedel, 1983). This included a good plasticizer
to soften the nitrocellulose polymer for shaping and molding, and a good
solvent (Ott, 1940; Friedel 1983). The Hyatts and Daniel Spill used cam-
phor, a natural extract from the wood and bark of the Japanese Formosa
tree, as a plasticizer from the outset for their cellulose nitrate plastics in the
1870s. The undesirable pungency of camphor and its cost at the turn of the
20th century led to the testing of no less than 44 chemicals and many deriv-
atives as substitutes (DuBois, 1907, p. 40-41), while oil of turpentine was
used in World War I because of camphor supply shortages (Mork, 1917).
Other alternatives were also trialed periodically (Sachs & Byron, 1921; Dur-
rans & Davidson, 1936), but camphor remained the best choice. Hyatt also
56 ANITA QUYE
decided on ethyl alcohol for the solvent and patented the important process
of ‘seasoning’ the finished product to allow all solvent traces to evaporate
for stabilization (Meikle, 1995).
With good choices of camphor plasticizer and ethyl alcohol solvent
from the outset, and awareness of residual acids and the benefits of antacid
stabilizers in place by the start of the 20th century, the industry had estab-
lished in its early days what chemists at that time considered to be the four
strong pillars of material stability for the plastic. The main advance for the
cellulose nitrate plastic manufacture in the 20th century was not so much
the chemistry of the material, but rather controlling the many variables
mentioned above during the production stages. Old industrial processes
were revisited and re-evaluated (Lunge, 1901), advancements made in cellu-
lose chemistry (Briggs, 1915), and the benefits of systematic applied chemi-
stry advocated to help solve industrial problems (Bacon & Hamor, 1919).
In 1920, Staudinger’s macromolecular theory classified plastics as polymers.
The crystalline structure of cellulose was revealed by X-rays one decade
later (Clark, 1930). By the end of the 1920s it was agreed that cellulose was
a polymeric chain of cellobiose monomers (Badgley et al., 1945), but the
direct impact of these major theoretical chemistry advances on cellulose
nitrate plastic quality was far less than might be expected. The chemical
process approach to esterification had changed very little since the begin-
ning (Yarsley et al., 1964, p. 173). Instead, the developments were more ad-
vantageous to manufacturing processes for the new related plastics made
from cellulose acetate and other cellulose derivatives.
By the 1920s interest was growing in colloid chemistry to measure
and characterize the viscosity of colloidon (Bancroft, 1922). This was dri-
ven further in the 1930s by the advent of fiber extrusion and injection-
molding for cellulose acetate, although this did not benefit cellulose nitrate
plastic much because these mechanical processes did not suit its flammable
tendencies. The advent of the ultracentrifuge in 1938 improved viscosity
measurements for cellulose nitrate plastics (Kraemer, 1938). However, the
chemical complexity and control over minute changes throughout the
whole process of making cellulose nitrate could not be overcome with the
extent of knowledge about colloid chemistry at that time (Conaway, 1938).
By the time polymer chemistry had matured in the 1940s, it was of more
value to the expanding fiber-making industries for filament extrusion of
viscose rayon and cellulose acetate, and for tailor-making cellulose deriva-
tives rather than improving cellulose nitrate plastics (Tinsley, 1948). The
rise of the more controllable petrochemical plastics proved too much com-
petition for the variances of cellulose nitrate (Meikle, 1995, p. 23). Cellulose
nitrate plastic was by now less appealing because its preparation was so sen-
QUALITY MATTERS FOR HISTORICAL PLASTICS 57
sitive, with even small changes in the equilibrium having unpredictable ef-
fects (Conaway, 1938).
Despite a steady increase in chemical research for commercial cellu-
lose nitrate manufacture from the 1910s to the 1930s, with a move from
small factory works to scientific institutions and industrial labs (Morris,
2015, p. 242-252), plus commercial and academic investment in research,
practical issues of variable chemical reaction parameters for cellulose nitrate
plastic could not be resolved. Eventually commercial manufacture started
declining in America in the mid-1950s amid competition from other better-
controlled synthetic plastics (Meikle, 1995, p. 28). In 1963, the few Euro-
pean companies still making cellulose nitrate plastic were working with old
equipment, while Japanese manufacturers used advanced technology
(Kaufman, 1963). By this date, cellulose nitrate was no longer produced in
the USA, but was still available and continued to be used for brush handles
and spectacle frames (Yarsley et al., 1964).
What does this overview of past cellulose nitrate plastic manufacture
offer to the conservation science of cellulose nitrate plastics? The upshot is
that despite progressive chemical understanding and a rise in research in-
vestment, there were surprisingly few major chemical step-changes for the
manufactured material. With regards to the common heritage science appli-
cation of material analysis to provenance the origin or date of an historical
object, the chemical composition of commercial cellulose nitrate plastic can
only enlighten us a little. The presence of a titanium opacifier would indi-
cate a date post-1916 and, with more research, camphor substitutes used by
different manufacturers, for example oil of turpentine derivatives, could be
linked to specific periods. Other factors like the design and style of the ob-
ject and trademarks would be more informative. Nonetheless, material in-
formation is still important to collect for preservation needs. For example,
oil of turpentine derivatives discolored imitation ivory (Sachs & Byron,
1921), so its presence in an aged object would predict or explain changes to
its appearance.
Gaining better appreciation of the quality challenges that the histori-
cal commercial makers faced to control vagaries in the process makes the
random degradation between similarly dated or produced objects more un-
derstandable. It is an inherent vice, yet this does not detract from the bene-
fits of analyzing degraded objects materials with well-known provenance,
instead enhancing further the material picture of production quality effects
and connecting material evidence to past written observations and tests.
58 ANITA QUYE
Changing Values of Brand Materials
The correlation between the chemical composition of artifacts and
their physical condition by Stewart was made possible by the direct analysis
of various artifacts, from good to poor quality. This invaluable primary
source research relied on collectors and curators appreciating that, in this
instance, de-accessioning and sacrificing a small number of historical ob-
jects would answer greater questions about stability to the benefit of many
more in heritage collections. Some de-accessioning decisions were justified
on the grounds that material breakdown had reached a critical point such
that the artifact no longer had significance or value in the context of the
collection and was also putting other parts of the collection at risk from the
emissions of its degradation products.
In this way, these historical materials inadvertently acquired a new
value for industrial heritage. While on one hand the degradation of material
culture can result in irretrievable or irreversible loss of the form or function
of artifacts, on the other these collections of historical materials enter a new
phase of historical value, becoming “monuments of history” as material
culture objects that reveal history and passage of time (Muñoz Viñas, 2005).
Thus, un-degraded and degraded historical cellulose nitrate plastics both
come to share significance and a material culture value for the conservation
scientist and industrial historian, where there are mutual interests in prod-
uct, production and quality. From its primary use as a brand material to one
as an historical object in a heritage collection, an artifact experiences its first
shift of significance. When it is removed from a collection because of de-
gradation, the same artifact acquires a second and new value, as an invalua-
ble material for experimental conservation science research into the
processes of aging and deterioration.
Especially valuable for direct primary source evidence from the past
are materials with well-documented provenance: where, when, and how
they were made. For conservation scientists, company archives of products
and production records provide significant historical clues. Detailed infor-
mation is also essential for reconstructions of historical processes as anoth-
er invaluable resource for technical history research (Staubermann, 2009). It
is as important to preserve and understand not just the manufactured end-
product but the raw materials and the manufacturing processes, and to pre-
serve manufacturers’ samples and associated knowledge through business
archives. Increasing digitization allows on-line access to publications from
the late 19th century and early to mid-20th century, such as Industrial and
Engineering Chemistry, where much was published about the early plastics in-
dustry and now becomes invaluable for documenting its growth and
changes. Access to these publications has significantly aided and enhanced
QUALITY MATTERS FOR HISTORICAL PLASTICS 59
research to connect artifacts and modern production for conservation
science, revealing an abundance of information from other chemical indus-
tries, such as the related synthetic fibers (Quye, 2014) and synthetic dyes
(Quye, 2016). Likewise, it is essential to preserve the physical evidence of
the products and documentation of production, and for conservation un-
derstanding to grow about materials for informed “interventive conserva-
tion”1 (Shashoua, 2016), and for collection management of artifacts and
archives (Brokerhof & Bülow, 2016). Uniting industry and historical ma-
terial culture in this way offers a potent reconnection between maker and
product.
Conclusion: From the Preservation of Materials to Interdisciplinary
Research
While there is an obvious desire to keep old cellulose nitrate plastics
‘alive’ so that their function, form and aesthetic can be appreciated and un-
derstood, their ‘death’ brings an unexpected insight into their material
composition and manufacture, with the process and products of degrada-
tion providing invaluable pieces of primary chemical evidence of past pro-
duction. Within the degraded plastic itself is a direct connection between
material stability, the chemistry of the manufacturing process, and quality
control during manufacture. Linking the chemical evidence in degraded and
un-degraded cellulose nitrate historical artifacts with contemporaneous
scientific accounts of their manufacture from those who understood the
scientific principles of manufacture brings those historians interested in 19th
century and early 20th century chemical manufacturing closer to direct pri-
mary evidence of quality control.
This a tale to emphasize that preservation of material culture makes
knowing and understanding industrial techniques valuable and necessary.
As observers with the gift of hindsight, we witness in cellulose nitrate plas-
tic a threshold amount of a known malignant acidic residue that was just
acceptable when made but has now become a destabilizing inherent vice
with time. That there was a need to rediscover a well-known phenomenon
first reported over a century ago and common knowledge until just 60 years
ago says much about how easily and quickly information is lost with the
decline of a commercial manufacturing industry. Research like Stewart’s
reconnects the material evidence in the historical object with past manufac-
1 “Interventive conservation” deals with the physical treatment of objects, like
cleaning or repair, whereas “passive conservation” seeks to control environmental
conditions such as temperature and humidity.
60 ANITA QUYE
turing method information, and revives the understanding to recognize the
significance of objects and their contextual information. In this case, a qual-
ity issue inherent in a past manufactured product has resurfaced as a conse-
quence of the material being kept by museums and collectors for longer
than the manufacturers could have expected.
Researching historical materials for conservation science entails three
essential aspects for meaningful and progressive insight: interdisciplinary
collaborations; access to digitized, searchable archives; and an understand-
ing of the chemistry of materials. The research described in this chapter for
cellulose nitrate would not have been successful without cooperative un-
derstanding between an analytical scientist, a polymer chemist, and a con-
servation scientist. Our multidisciplinary discussions gave insight into the
past industrial production of a material and connected the research to the
history of science. In short, the breakdown of an inanimate material
brought a new community of people together in a dialogue where chemis-
try, conservation and history had to be articulated and interconnected.
The study presented is by no means a unique example of how pre-
servation brings insight to past technology and production quality. Colla-
borative research between conservation scientists at the Kunst Historische
in Vienna and historians revealed that the unexpected and unlikely corro-
sion of gold coins minted in the 19th century. The problem transpired to be
the dies, carrying traces of contamination iron from other coins onto the
surface of the gold coin (Traum & Griesser, 2006). Taking a look beyond
what is happening to the aged material now and placing its present chemical
condition in the context of its production takes historical materials research
beyond issues of current preservation state into the realms of technical
production and industrial quality.
The multidisciplinary collaboration of material chemists and heritage
scientists, and knowledge exchange with curators and historians of technol-
ogy and industry is enlivening, indeed vital, when the maker’s voice is lost.
Access to historical manufacturing information greatly assists conservation
scientists and conservators in their quest to understand more about original
modern industrial materials. At this point in time there are many examples
of historical cellulose nitrate, but with loss through degradation, preserva-
tion of these once common mass-produced objects becomes even more
pressing especially if other sources of related information disappear (Muñoz
Viñas, 2005).
While any loss of material culture is lamentable to its collector and
custodian, especially when the object loses significance because it is no
longer physically intact nor accessible in its broadest sense, or becomes a
health hazard or is detrimental to other artifacts, it can attain a new role
QUALITY MATTERS FOR HISTORICAL PLASTICS 61
within historical and socioeconomic frameworks. An historical object tra-
vels different paths in its journey through the material culture world where
it will be judged by our changing perspectives on value and significance. It
may seem that the end of its useful ‘life’ will be the day when the object
loses its material coherence and physically breaks down. To the materials
scientist, this point can be the start of a new journey of discovery. Even if
an object can no longer be used or understood, like the spectacles in Figure
1, its degraded material composition is a bridge to an otherwise distanced
world of its creation.
In the context of stabilization of cellulose nitrate plastics, the endea-
vors of the industrial chemists testing the quality of the material for the
consumer lifetime of the material are similar to the conservation scientists’
testing of the composition of aged material to extend the artifact’s lifetime.
The connections among chemists, polymer scientists, engineers, and indus-
trialists in the historical production of brand plastics are mirrored in the
knowledge exchange community of chemists, conservation scientists, con-
servators, historians, and curators for the promotion and conservation of
material collections. When quality matters for industrial heritage, historical
objects benefit from new conversations in history of science for material
significance and preservation.
Acknowledgment
The author would like to thank the Engineering and Physical
Sciences Research Council and the Scottish Conservation Bureau of Histor-
ic Scotland for their financial support for Robert (Robbie) Stewart’s re-
search. She is also indebted to Robert Stewart, Dick Pethrick, David Little-
john and Colin Williamson for their interdisciplinary collaboration, Klaus
Staubermann for constructive and insightful comments on this manuscript,
the reviewers for inspiring recommendations and additional references, the
editorial team for honing the text, Yvonne Shashoua and the National Mu-
seum of Denmark for the photographs, and Julie Wertz and Brigitte van
Tiggelen for translation assistance and proof-reading.
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