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Adverse Effects of Hot-Melt Cyclododecane on Red Printing Inks Carina Rosas
Northumbria University, MA Conservation of Fine Art
Interaction assessed by extent of CDD colouration, presumed due to pigment extracted by the cycloalkane
This solvent-like behaviour appeared only to occur with CDD in the molten (liquid) state
Extent of interaction was found to increase with higher temperature or prolonged application (increased molten
time), the latter exemplified by the significant difference in CDD colouration when driven through the paper
compared to hot-melt application alone (Figs 7 and 8)
REFERENCES
Brückle, I., Thornton, J., Nichols, K. and Strickler, G. (1999) ‘Cyclododecane: Technical Note on Some Uses in Paper and Objects Conservation’, Journal of the
American Institute for Conservation, 38, pp. 162–175.
Herbst, W. and Hunger, K. (2004) Industrial Organic Pigments: Production, Properties, Applications. 3rd Revised Edition. Weinheim: WILEY-VCH.
Larsen, L. M., (1962) Industrial Printing Inks. New York: Reinhold Publishing Corporation, London: Chapman & Hall, Ltd.
Rowe, S. and Rozeik, C. (2008) ‘The Uses of Cyclododecane in Conservation’, Studies in Conservation, 53, Supplement 2, pp. 17-31.
Thank you to my supervisors Dr Charis Theodorakopoulos and Dr Jane Colbourne, as well as Panos Galatis and Alfons Bytautas for their support and assistance
INTRODUCTION
CONCLUSION Molten CDD displayed differing degrees of solvent-like behaviour with a range of red pigments, extracting them from
their binder matrix. The extent of this interaction was found to be temperature and time-dependent. Most ink
surfaces tested were not visibly altered by the extraction of coloured components. Whilst it falls on the conservator
to judge whether the changes effected are an acceptable compromise in the light of the clearly recognised benefits
of using CDD, its complex and potentially problematic chemical behaviour warrant careful consideration prior to use.
Further research is certainly required. Identification of both coloured and non-visible components susceptible to
solubilisation by hot-melt CDD is imperative to determine immediate and long-term consequences of its application
in conservation treatments. As the use of cyclododecane expands both within the range of treatments in which it is
applied and across conservation fields, its risks need to be acknowledged and identified to enable its safe use. The
present study hopes to contribute to this.
Cyclododecane (CDD), C12H24, is a cycloalkane used since 1999 in paper conservation as a
fixative for water-sensitive media. Its uses have since expanded to other purposes requiring
temporary adhesion such as facing and attachment of thermal sensors to historic wallpapers in
situ.
CDD displays highly beneficial properties for conservation use, including its ability to sublimate
at room temperature and standard atmospheric pressure without leaving appreciable
residues, its film-forming properties, insolubility in water and low melting point (58-61°C).
However, as with all relatively new materials, the potentially damaging effects of its use have
not yet been established. When first proposed for use in conservation in 1995 by Hangleiter,
Jägers and Jägers, caution was recommended regarding potential solvent-like behaviour of the
cycloalkane towards non-polar materials such as certain resins, oils and waxes, although these
were unspecified. Since then, anecdotal evidence has suggested widespread incompatibility
issues regarding paper artefacts, with caution having been advised in the presence of heat- or
solvent-sensitive constituents, a somewhat generic recommendation that provides limited
guidance for conservation practice.
Presently the success of its use is somewhat unpredictable, as its chemical behaviour is not yet
fully understood and the specific materials with which it interacts have not been identified.
A pilot study is being conducted on the adverse effects of CDD on red oil-based printing inks,
through the assessment of its interaction with a group of early 20th Century commercial
entertainment poster inks (dated 1910-1947). This study focuses on potential solubility of
synthetic organic pigments in hot-melt CDD. The susceptibility of this group of materials to
chemical interaction with the cycloalkane has to date not been explored.
EXPERIMENTAL 1. CDD was applied to 20 red poster inks, following methods consistent with the literature:
Using heated spatula fitted with a small bowl wax applicator, set to 74°C (Fig 4). Assessed
by touching a strip of Whatman filter paper on the CDD-treated area whilst still liquid
CDD re-melted in situ, using a heated spatula set to 60°C, until it had penetrated the
substrate completely (Fig 5). Assessment by collecting residues from verso on a section of
Whatman filter paper placed beneath substrate (Fig 6)
2. Ink surface was assessed after sublimation (optical microscopy, spectrophotometry)
3. Analytical techniques supported by technical art historical context to infer pigments
Coloured CDD collected and allowed to sublime. Residues tested (in progress)
Figure 7: Hot-melt application alone: Colouration
visible for 1 of 20 inks (minimal extent)
Figure 8: Hot-melt application followed by driving CDD through the objects substrate:
CDD was visibly coloured with 11 of the 20 inks, to differing degrees
ΔL* Δa* Δb* ΔE*ab
Ink 3 6.68 -7.59 -2.73 10.47
Ink 12 -2.88 -1.58 -5.47 6.38
Ink 13a -5.26 -4.84 -11.04 13.15
Ink 13b -3.27 -4.25 -7.6 9.30
Table 1: Colour difference (ΔE*ab)
for Inks 3, 12, 13a and 13b*
Figure 1: Object 5 (1930)
Offset lithographic ‘blank’
poster, letterpress overprint
Figure 3: Object 13 (1941)
Letterpress ‘blank’ poster,
letterpress overprint
Figure 2: Object 12 (1941)
Letterpress printing
RESULTS
1. Cyclododecane application
Figure 4: Hot-melt CDD applied using a
heated spatula fitted with a wax applicator
Figure 5: CDD was subsequently ‘driven
through’ the paper using a heated spatula
Figure 6: Coloured CDD collected on underly-
ing paper (right) after driving through object
2. Ink surface assessment after CDD sublimation
Figures 11a-c: Coloured CDD (Ink 3) was collected to identify extracted constituents by further analytical techniques. Possible chemical inter-
action with pigment indicated by colour change, with bright yellow-orange colour when molten, changing to a dull pink hue upon freezing
Figure 10: Heat testing on Ink 13a
indicated colour shift was heat-related
16 inks displayed no visible surface changes after sublimation
4 inks were visibly altered:
Ink 3 displayed discernible loss of colour (lighter tone) detectable with the naked eye (Table 1, Fig 9)
Inks 12, 13a and 13b displayed visible, albeit slight, hypsochromic colour shifts (bluer hue) corroborated
by colorimetry (Table 1). Spot testing using heat alone confirmed this as a heat-related shift (Fig 10)
Figures 12a-b: Upon sublimation, extracted components accumulated on the CDD surface, forming intensely coloured residues. Ink 12
Figure 12c: Extracted components penetrated underlying Whatman filter paper as sublimation progressed, producing a pink/orange stain. Ink 12
ONGOING WORK: Pigment identification
During preparation of samples for analytical techniques:
Coloured CDD displayed bright colouration when molten (Fig 11a-c)
Components extracted from the ink reformed on the CDD surface (Fig 12a and 12b) and penetrated the
paper (Fig 12c) during sublimation. Their intense colouration indicates presence of pigment
Analytical techniques (FTIR, PyGCMS) currently underway to identify extracted constituents, followed by assess-
ment of possible correlation between chemical structure of pigments and their tendency to interact with CDD
Technical art historical context of red pigments used in printing inks:
Posters assessed in present study presumed to contain synthetic organic pigments, likely of an azo class, considering their dates and application
(commercial, short-term use). Azo pigments are the largest synthetic organic class, comprised mainly of red, orange and yellow pigments.
Until late-19th century, inorganic and lake pigments were used, the latter technically complex to produce, a task performed by printers themselves
Following the development of the first azo dye-pigment in 1885 (Para Red, PR1), a large quantity of new azo pigments and lakes with ever-increasing
quality and permanency were synthesized in the first decades of the 20th century using the coupling components β-naphthol and Naphthol AS
These quickly superseded other colourants due to their low cost, ease of use (pre-prepared), bright and unusual hues and improved printing properties
ACKNOWLEDGEMENTS
Contacts: [email protected] [email protected]
Control
(CDD)
1 2 3
Control
(CDD)
1 2 3 4a 4b
5a 5b 6 7 8a
8b 9 10a 10b 11
12 13a 13b
* JND (just noticeable difference) at ΔE*ab ≈ 2.3 Figure 9: UV-VIS spectrophotometry (Ink 3) indicating
increase in surface reflectance, due to loss of pigment
0
10
20
30
40
50
60
70
80
180 280 380 480 580 680 780
% R
efle
cta
nce
Wavelength (nm)
Ink 3
Untreated ink After CDD application and sublimation
a b c
a b c
14 15
4a 4b
5a 5b 6 7 8a
8b 9 10a 10b 11
12 13a 13b 14 15
2mm ______________ 2mm ______________ 2mm ______________
