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The Conservation of Acrylic Emulsion Paintings: A Literature Review



Acrylic emulsion (or more accurately dispersion) paints present major challenges to paintings' conservators, yet remarkably few studies of these materials have been published. The intent in this paper is to present the conservation information that does exist in a concise format to expedite much needed further discussion and research by conservators, paint manufacturers and artists. Brief descriptions of the development and analysis of acrylic emulsion paints are given, but the focus of this review is on conservation concerns, in particular issues surrounding the paints' properties, ageing and cleaning.
The Conservation of Acrylic Emulsion Paintings: A Literature Review
By Elizabeth Jablonski, Tom Learner, James Hayes and Mark Golden
Acrylic emulsion (or more accurately dispersion) paints present major challenges to paintings’
conservators, yet remarkably few studies of these materials have been published. The intent in this paper is
to present the conservation information that does exist in a concise format to expedite much needed further
discussion and research by conservators, paint manufacturers and artists. Brief descriptions of the
development and analysis of acrylic emulsion paints are given, but the focus of this review is on
conservation concerns, in particular issues surrounding the paints’ properties, ageing and cleaning.
Acrylic emulsion artists’ paints were received with much fanfare and excitement in the 1950’s and 1960’s.
They embodied the characteristics that many artists had been searching for at that time, affording a means
of expression that was distinct from oil painting and its associated history and traditions. As Kenneth
Noland expressed it, "the materiality and actual work process became more present [1]." These synthetic
paints produced films of great clarity and phenomenal elasticity, were easy to manipulate, could be painted
directly onto supports, dried quickly, were thinned with water and exhibited high resistance to ultraviolet
degradation. John Hoyland recalled “I remember reading articles in magazines. They talked about the
radiance of [acrylic paint] and the fluidity of it… and that it would never yellow. It seemed exciting in the
way people got excited about the use of plastics, aluminium and other industrial materials [2, p. 101]”. And
Helen Frankenthaler, who switched from using oil paints to acrylic emulsions in the early 1960s, said:
“I changed to acrylics for a number of reasons. Once, I was told that they dry faster, which they
do, and that they retain their original colour, which they do. I would say durability and light and
the fact that one can use water instead of turpentine: all that makes it easier given the abstract
image…. As painting needed less and less drying time, depth, and so forth, the materials came
along that made that more obvious [3 p. 82]”.
In spite of their outstanding mechanical and aging properties, acrylic emulsion paintings do suffer damage,
often through external influences. Within the conservation profession, concerns were soon raised as some
of these newly painted works began to require cleaning and repair [4,5]. Similar themes were discussed in
the following decades [6,7,8].
Essentially, three fundamental problems were identified. The first was that most conservation treatments
had been designed for traditional oil paintings and were found unsuitable for acrylic emulsion paintings,
due in particular to the high sensitivity of these synthetic paints to the majority of organic solvents and heat.
The second was the complete lack of knowledge about these acrylic emulsion systems, especially the
complexity and constant changes to the formulas, with insufficient information coming from the
manufacturers of both raw materials and artists’ paints. And third, damage may be especially noticeable in
colourfield or monochromatic paintings, as a disruption to the delicate surface texture, colour or gloss
[1,8,9], all of which are often integral to the artists’ intent and can be altered by even the slightest contact.
Even small damages can therefore soon become ‘unacceptable’. Since remedial treatment is so difficult
with acrylic paintings, preventive conservation is crucial [10].
In general, very few studies of the conservation of acrylic emulsion paintings are published. Instead,
concerns tend to be communicated through informal discussion. The intent in this paper is to review the
available information from conservation literature and to encourage further discussion and research by
conservators, conservation scientists, paint manufacturers and artists. It should be stressed that this review
only takes into account publications in the English language and a broader understanding of the subject
would be possible from surveying material written in other languages, in particular the work of Röhm in
Germany, who first reported the production of a solid acrylic polymer in 1901 and developed a commercial
synthesis of acrylate esters in 1927 [11,12]. It also does not review the incredible developments that have
taken place with organic and inorganic pigments, although good accounts of these exist already (e.g.
The conservation concerns with acrylic paint media tend to fall into three categories and will be presented
as such: the Development of Waterborne Acrylic Artists’ Paints, Paint Properties, Aging Properties and
Cleaning Issues.
Henry Levison, a chemist-turned-paint maker, founded the company Permanent Pigments in 1933, which
produced the first line of waterborne acrylic emulsion paints called Liquitex® in 1954 [14]. He often
supplied artists in exchange for soliciting their advice and occasionally hiring them as consultants or staff.
The development of Liquitex® came a few years after the introduction of the first artists’ acrylic paint,
Magna®, by the paint makers Leonard Bocour and Samuel Golden in 1947-49. Magna® acrylic paints
were solution paints, and quite distinct from waterborne emulsion paints. In practical terms, Magna® dried
quickly by evaporation of organic solvent, remained resoluble in many hydrocarbon solvents as well as
further layers of paint and could be blended with oil paint [15,16,7]. In contrast, the drying process of
emulsion paints involves a complicated coalescence of emulsified polymer spheres after an initial
evaporation of water; these paints become insoluble in water - and further layers of emulsion paint - after
they have dried.
Confusingly, many terms are used to refer to waterborne acrylic paints, such as ‘acrylic paints’, ‘acrylic
emulsions’, ‘latex’, and ‘polymer colours’. In fact, technically, they are ‘dispersions’ rather than
‘emulsions’, because they are composed of tiny beads of solid, amorphous polymer suspended in water.
The fact that these paints could be diluted and thinned with water, instead of mineral spirits, made them -
and continues to make them - very appealing to artists. The raw polymer emulsions used by artists’
colourmen and paint makers were frequently those from Rohm and Haas’ Rhoplex® series of products
(known as Primal® in Europe), such as AC-22, AC-33, AC-234 and AC-634. Rhoplex® AC-33 first
became available in the 1953. All of these emulsions were copolymers, utilizing the harder methyl
methacrylate (MMA) and softer ethyl acrylate (EA) to create the required working properties (e.g.
flexibility) and durability for house paints, their primary market. Since the end of the 1980’s many of the
resin formulations have changed to a poly (n-butyl acrylate/methyl methacrylate) copolymer, such as
Rhoplex® (or Primal®) AC 235. These films tend to be slightly tougher and more hydrophobic than the
pEA/MMA resins, making them more durable to outdoor exposure. Styrene has sometimes part or wholly
replaced the MMA component to save manufacturing costs [17,12,18].
Acrylic emulsions contain a multitude of additives that determine the performance properties of the paint,
from shelf life to application and longevity, to health and safety properties [19,20,21,18,22]. They are
included at two distinct stages of production: during the manufacture of the emulsion polymer and during
the formulation of the paint itself. With the exception of a few volatile additives (see below), all additives
remain in the dry paint film. Research into their interaction with the binder is therefore necessary for a
complete understanding of the aging properties and effects of treatment on acrylic emulsion paints.
However, almost nothing has been achieved towards this, either analytically or from manufacturer’s
information, on their precise identity. While the paint formulator knows the basics of these materials,
proprietary materials are frequently incorporated by the manufacturer of the additive, and the additives
themselves are constantly changed to meet the needs of the large coatings industry [20,23].
Additives in the emulsion binder
Initiators: used as a source of free radicals to initiate the polymerization process - in which monomers
condense to form the polymers. These are most often persulfates, e.g. potassium persulfate [24], which
thermally decompose to form free radicals. The polymer manufacturer may also use a redox system,
adding ferrous and thiosulfate along with the persulfate salts, to allow for room temperature reaction
Chain transfer agents: incorporated to aid in controlling/limiting molecular weight (MW) during
polymerization, for example dodecyl mercaptan [26].
Buffers: typically ammonia, added to maintain a pH of eight to ten, for maximum dispersion stability
of the acrylic polymer.
Surfactants: a critical group of components, necessary to create the micelles for particle formation, as
well as long-term particle stabilization. Common surfactants are non-ionic (e.g. alkyl phenol
ethoxylates) and anionic (e.g. sodium lauryl sulfate or dodecylbenzene sulfonate), typically added in
two to six percent by weight (%/w) [25]. These provide stability through electrostatic and steric
hindrance mechanisms.
Protective colloids: these also contribute to steric stabilization and are water-soluble natural or
synthetic polymeric emulsifiers such as hydroxyethylcellulose and polyvinyl alcohol, added in one to
ten %/w.
Preservatives: generally added in low doses (less than one %/w) to protect against growth of
microorganisms and are commonly methyl benzisothiazolinones, chloromethylisothiazolinones,
barium metaborate and formaldehyde donors, such as 1-(3-chloroallyl)-3,5,7-triaza-1-
azoniaadamantane chloride.
Residual acrylic monomers, generally in the 50 – 1000 ppm range, are also present, resulting from
incomplete polymerisation.
Additives utilized by paint formulators to achieve the intended performance properties.
Wetting and Dispersing Agents: added to wet pigment surfaces, allowing pigment agglomerates to
break apart - a critical process in developing color strength - and providing steric and/or electrostatic
stabilization of the pigments. Typical wetting agents include alkyl phenol ethoxylates, acetylenic
diols, alkylaryl sulfonates and sulfosuccinates [27], i.e. similar to the surfactants used during
polymerization. Dispersing agents are typically polyphosphates (generally calcium or potassium salts
of oligophosphates with two to six phosphate units) or polycarboxylates (sodium and ammonium salts
of polyacrylic acids 2,000 – 20,000 MW) [24].
Coalescing Solvents: added to insure film formation under varying atmospheric conditions. They are
slow evaporating solvents with some solubility in the polymer phase. They act as a temporary
plasticiser, allowing film formation at temperatures below the system’s glass transition temperature
(Tg) [25], after which they slowly diffuse to the surface and evaporate, increasing the hardness and
block resistance of the film. Typical coalescents are ester alcohols, e.g, Texanol® (Eastman Chemical
Co.), benzoate esters, e.g. Velate® (Velsicol Chemical Co), glycol ethers, glycol ether esters and n-
Defoamers: necessary to reduce the inherent tendency of emulsions to foam, a consequence of
incorporating surfactants. Defoamers are typically mineral oils or silicone oils. Silicone oils
(polydimethylsiloxanes) are much more efficient and active, but more likely to produce film defects
(craters, fisheyes, etc.). The mechanism by which defoamers function is not fully understood, but
essentially these very hydrophobic materials are thought to move to the air-liquid interface, allowing
the air to release [24,25].
Preservatives: although acrylic emulsions typically have preservatives in them as supplied, additional
preservative is added to avoid the effect of dilution as water and other components are added. The
same preservatives (listed above) are used.
Thickeners and rheology modifiers: required to achieve the desired viscosity and flow properties.
Thickeners function through multiple hydrogen bonds to the acrylic polymer, thereby causing chain
entanglement, looping and/or swelling which results in volume restriction. The most common group is
cellulose derivatives, including hydroxyethylcellulose, methylcellulose and carboxymethylcellulose.
Also important are alkali-swellable polyacrylate emulsions, which add considerable viscosity upon
neutralization with an appropriate base (such as ammonia). Polysaccharides such as xanthan and guar
gums are also used. A relatively new group of organic rheology modifiers (altering rheological
properties more than building viscosity) is the hydrophobically-modified ethoxylate urethanes
(HEUR). Inorganic thickening agents can also be used, such as forms of bentone clays, including the
bentonites, smectites and attapulgites, and fumed silicas.
Freeze-thaw Stabilizers: if a waterborne paint freezes, ice crystals will form, thereby disrupting the
dispersion stability and causing permanent damage through polymer coagulation. However, the
incorporation of two to ten percent ethylene or propylene glycol ensures the water, surfactants and
protective colloids will return to the acrylic emulsion surface in an orderly way [26].
There is a need for conservation-driven research, publications and interviews with artists about their chosen
materials, reasons for using them and thoughts on the conservation of their work. Several papers have
presented the history of the manufacturing of artists’ acrylic paints and their commercial introduction to
artists [2,7,14]. Marontate [14] presented in-depth interviews with paint manufacturers and their early
concerns for the durability of the materials, resulting in organizations such as the American Society for
Testing and Materials. Lodge [7] presented a concise review of the history of the modern synthetic paints
in the hands of artists. In addition to charting the manufacturing history of modern synthetic paint media,
Crook and Learner [2] conducted detailed studies of several artists, their materials and the construction of
their paintings.
Several museums have established programs of artists’ interviews either on audio tape or video, or through
written questionnaires about specific artworks, typically upon their acquisition. Many issues can complicate
the gathering of such information, for instance, the artist may not recall his exact materials or may provide
contradictory information [28,29,30,33,31,32]. All of these issues were extensively considered and a
methodology of interviewing artists proposed in the symposium and publication, Modern Art-Who Cares?
[30,33,34]. The importance of using scientific analysis to confirm an artist’s recollections has been stressed
Several papers have now appeared on methods of scientific analysis and chemical characterisation of
acrylic emulsion paints. Essentially, it is now possible to identify the major components in an acrylic paint,
i.e., binder, pigment and extenders. The three main techniques have been Fourier transform infrared
spectroscopy (FTIR) [35,36,37,17,38,12,39,40,41,22], pyrolysis - gas chromatograpy (Py-GC) [42,43,22]
and pyrolysis - gas chromatography - mass spectrometry (Py-GC-MS) [37,17,12,44]. In addition, direct
thermally resolved mass spectroscopy (DTMS) has been shown to be effective at identification of acrylic
binders and the majority of pigments [45,12]. However, the use of ultraviolet (UV) fluorescence
microscopy staining gave inconsistent results for layers of acrylic in cross-sections [22], perhaps an
inevitable consequence for such complex formulations. The analysis of additives, however, is very scarce;
with the exception of recent FTIR studies that have identified poly (ethylene glycol) (PEG)-type surfactants
[46,47]. This may support the presence of alkyl phenol ethoxylate surfactants, which are common to the
coatings industry.
Other characteristics of acrylic emulsions have also been studied. The relative proportion of each monomer
in copolymer emulsions was measured by nuclear magnetic resonance (NMR) [48] and thermomechanical
analysis (TMA) [12]. Molecular weight distributions of the soluble component and an estimate of the
degree of cross-linking in dried films were made by size exclusion chromatography (SEC) and
thermogravimetric analysis (TMA) [48,46]. And scanning electron microscopy (SEM) has been used to
document film coalescence and topography [49,19,50].
Film Formation
The basic process of film coalescence has been described frequently in the conservation and paint industry
literature, though authors acknowledge the over-simplification of this model [51,52,53,54,55,50,,56,57].
Acrylic emulsions are composed of particles of amorphous polymer suspended in water. The two-phased
system is held in suspension by surfactants and/or other surface stabilizers. During drying, water
evaporates to draw the spherical polymer particles closer, which then meld together to form a ‘honey comb’
network. A coalescing solvent additive ensures the polymer particles remain malleable during - and
beyond - this process, to produce more complete compaction, even after the water has evaporated.
Eventually, the boundaries between particles become barely detectable and the film is considered
continuous. However, it has been shown that pores or microvoids are often left within the film, readily
seen with light microscopy and scanning electron microscopy [58,59,60,61,22,50,62].
The degree of coalescence is dependent upon a variety of conditions, including the ambient conditions
during drying, the Tg - approximately 10°C for pEA/MMA emulsions [12,18], minimum film formation
temperature (MFT), modulus of elasticity and viscosity of the resin, as well as the function of additives
such as coalescing agents [63,53,6,64,56]. Paints left to dry slightly below their Tg and MFT will result in
films of higher porosity. A paint drying significantly below its Tg will form a loose, powdery layer [65].
Film porosity and pin-holes
The porosity of acrylic emulsions was exploited early on in the coatings industry. Acrylics were ideal as
coatings for wood because they allowed water vapour to pass through them, reducing the risk of
delamination on exposure to moisture [66,53]. However, porosity in an artwork coating has obvious
conservation implications: dirt and air pollution may become trapped, making removal difficult and
providing a haven for biological growth [67,68,69].
Similar concerns were raised in all these publications about pin-holes, or craters, which are often produced
in emulsion paints as a result of the foam created during both manufacturing and application of the paint
[20,22], although this phenomenon can occur in other types of paint, even oil-based media. It has also been
suggested that voids may trap conservation cleaning agents through capillary action, possibly causing long-
term damage [70]. In the case of outdoor murals, efflorescence of the substrate or the formation of ice
crystals can occur, causing a build-up of material on the surface or between the coating and substrate
A phenomenon sometimes observed in clear acrylic emulsion films is haziness. Under natural and
accelerated aging conditions, haziness was observed in young films of Liquitex® Acrylic Gloss Medium
[47]. The haziness was composed of microscopic spherulitic crystals on the surface of the acrylic film, as
characterized using light microscopy. These water-soluble crystals formed as the temperature and relative
humidity (RH) of the films increased. FTIR revealed that the crystals contained compounds similar to those
found in PEG of about 1500 MW. It was predicted that crystals might develop if the temperature was
between the melting point of the crystalline material and the Tg of the polymer. At that point, the PEG-type
material would be free to migrate through the film and crystallize. Proposed temporary solutions were
either to raise the temperature of the film to melt the crystals once formed, or to keep the film temperature
below its Tg, i.e. to prevent crystal formation. The risks associated with both techniques were mentioned.
A different type of haziness or cloudiness has also been reported, which can occur during the drying
process before all the water has evaporated, or when coalescence is incomplete, leaving pores or
microvoids within the film [58,59,60,61,50,62].
The temperature sensitivity of acrylics can be problematic, especially while paintings are in storage or
transit. Their low Tg makes them rubbery at room temperature, attracting dirt and airborne pollution. High
temperatures and RH can cause packing materials to stick to a painting’s surface. In one reported instance
[71], an acrylic painting on paper by Sam Francis became adhered to its Perspex™ glazing , although
separation was possible by localized applications of a heated spatula to the front of the Perspex™.
Low temperatures and RH are particularly damaging, as they can cause a significant decrease in elasticity
of the paint film and consequent cracking of the paint upon flexing, as demonstrated by Erlebacher et al
[72,73]. Emulsion films were exposed to various temperature and RH combinations and their strength,
modulus and elongation at break were measured. In general, the strength and stiffness of the films
increased as the temperature and RH decreased, particularly under conditions of 40-50% RH at 15 °C and
below. However, at very cool temperatures, such as -3°C, the strength actually began to decrease, as well.
At 40% RH, brittleness occurred at 5 °C, but at 5% RH this figure rose to as high as 11°C. The warning
was clear that cold temperatures and low RH, feasible winter conditions, make acrylic emulsion paintings
brittle and susceptible to cracking.
Conversely, a warm, humid environment, even if only experienced during shipment, can encourage mould
growth, as reported by Gatenby [69]. In this case, loose mould and dirt were removed by dry brushing and
vacuuming and then with distilled water and non-ionic surfactant. However, this treatment was complicated
further by the matte and powdery nature of the paint; the mould left black stains in some areas of the paint.
Properties of additives
Although most additives remain to be studied in-depth, recent attention has been focused on the effect of
the surfactants. These have been located in dried films, especially within the subtle boundaries among the
coalesced polymer beads [74,58,52,55,75,56]. It has also been suggested that surfactants (and other
additives) migrate to both the surface of the film and the film/substrate interface
[76,77,78,79,80,81,54,75,82,47,62,56]. The migration occurs at several stages: first, during application of
the paint to the substrate, as a way of breaking the surface tension and allowing the paint to wet-out the
substrate [79,80]—porous substrates can absorb surfactant [83,65]; second, during drying of the paint film,
when capillary action forces water and water-miscible additives to the film surface [60,84]; and third, after
drying, upon elongation of the film [80]. Surfactants on the film surface may change its gloss, both in
degree and uniformity, cause adhesion failure of varnish [21], and harbour dirt and biological growth [85].
It is also likely to foam and be susceptible to removal during surface cleaning [76,77,21]. The effect of a
surfactant’s presence on the mechanical properties of the dried film is being investigated [86].
Clear acrylic paint media were observed to yellow or discolour slightly in three studies. In the first, an
artist had observed yellowing of GOLDEN® clear acrylic medium in one of his paintings prompting a joint
research project between Golden Artist Colors, Inc. and the Buffalo State College Art Conservation
Program [87]. A variety of non-pigmented artist's acrylic media were submitted to both natural and
accelerated aging. Discoloration was noticed in the samples applied to cotton and linen supports, more so
than in those applied to glass. The discoloration appeared shortly after the samples had dried; accelerated
aging did not significantly increase yellowing. The discoloration was attributed to the migration of
components from the support into the medium during drying. The water in the media dampened the support
and components within, such as size, dirt and degradation products, and, upon evaporation through the film
surface, pulled the decolourants into the media. This support-induced discoloration (SID) can be avoided
by thoroughly washing the canvas or linen with water before use.
Yellowing of clear acrylic emulsion media was also noticed during another study [88]. The samples of clear
acrylic media, supported on glass plates, exhibited slight yellowing (and an increase in UV fluorescence)
after natural aging in the dark, light aging and oven-aging. The yellowing was more intense in the thickest
areas of the film and not confined to the surface. During the aging process, the films were submitted to
periodic solvent extraction to monitor changes in MW through viscosity. The increase in yellowing
coincided with a decrease in solubility. Naturally aged films became increasingly insoluble in benzene two
weeks after application, exhibiting partial swelling instead, and after sixty days the samples became so
insoluble that elevated temperatures were necessary for dissolution. The yellowing was attributed to slight
cross-linking of the film. It was proposed that even though chromophores are not present in the initial
formulation of the acrylic, their development may be catalysed by other reactions within the film.
Finally, in an additional study by Whitmore et al [89], the yellowing of clear acrylic films in the dark was
explored, providing evidence that they can be bleached in the light, to varying degrees, as can oil paint;
films with SID are less susceptible to light-bleaching.
Cross-linking and Oxidation
References to cross-linking in waterborne acrylic emulsions are intermittent. Cross-linking can occur at
three stages: during the polymerisation/production of the raw polymer resin; during drying/coalescence of
the paint film; and during aging (both natural and accelerated) of the dried film. Acrylic emulsions can be
formulated to undergo varying degrees of cross-linking during drying, depending on the end use of the
product, using additives called ‘cross-linkers’; however, these are not thought to be present in artists’
emulsion paints [19,90,55]. Instead, the high MW of the polymer is enough to provide high film strength
from chain entanglement [53,55,91]. It has been reported that during aging, a film can cross-link and
oxidise as a result of photo-degradation [92] and from the effect of residual surfactant [65], however, while
Chiantore (76) detected cross-linking in sample films, both before and after aging, oxidation products were
not found. The principal consequences of cross-linking are an increase in brittleness [93,65] and hardness,
which may actually improve the film’s resistance to dirt pick-up and abrasion [94].
Effect of pigments
Inclusion of pigments tends to stabilize the binder, as they are often effective UV absorbers. Inorganic
pigments tend to offer improved durability in comparison to the organics. Titanium dioxide is probably the
most studied pigment. Of the two different crystalline forms, rutile, rather than anatase, is appropriate for
exterior paints because it is far less reactive to ultraviolet radiation. Anatase, highly reactive to ultraviolet
radiation, can form radicals and degrade the polymer [24].
Recently, Klein [95, p.2] conducted a census to “determine the most commonly used methods and
materials used by painting conservators in their treatment of acrylic paintings”, although out of 190 surveys
sent to paintings conservators in North America, only 31 were completed. In addition, 41 letters of refusal
were returned, citing reasons such as insufficient experience in treating acrylics and lack of time or staff to
fill out the survey. It was confirmed that many conservators treat acrylic artwork with products and
techniques developed for traditional paintings, and more conservators considered themselves ‘self-taught’
in the treatment of acrylic paintings as opposed to trained during their university program. By far the most
common treatment problem encountered on both unvarnished and varnished paintings was some form of
cleaning, typically requiring the removal of dirt or marks from vandalism. A wide range of cleaning
materials and methods were identified, principally dry methods, such as brushes and erasers, and aqueous
methods, i.e. saliva or water, often with small additions of ammonia, surfactants or triammonium citrate, or
even baby wipes. However, a range of organic solvents and solvent gels were also cited. Some of the major
concerns of the participants were the difficulty of grime removal, the sensitivity of the paint, leaching
during aqueous cleaning, identifying the specific components of the media, the application and future
removal of varnishes and the protection of unvarnished paintings from deterioration.
Affinity for Dirt Pick-up
Frequently mentioned in the literature, yet rarely analysed is the tendency of an acrylic emulsion paint film
to imbibe surface dirt. Dirt can come into contact with the painting through airborne pollutants, handling
(e.g., fingerprints) and accidents or vandalism. It has been suggested that indoor air pollution,
accumulating gradually on a painting surface, may take approximately 50 years to become perceptible to
the human eye [96,77]. The principal factors thought to affect the attraction of dirt to acrylic paintings
mentioned in the literature include:
Tg, MW, MFT and softening point of the acrylic resin: if all are low, then the resulting film exhibits a
low hardness at room temperature, forming a tacky ‘trap’ for incidental dirt [97,98,6,7].
Static charge: acrylic paint films are non-conductors and can, therefore, accumulate a static charge,
attracting dust from the air [37].
Pigment concentration: it has been suggested that high pigment load can block dirt pick-up [99],
however, it is likely that the uneven surface resulting from a paint of high pigment load would trap dirt
mechanically, and therefore significantly increase the difficulty of dirt removal.
Hydrophilic additives, such as surfactants: such additives located at the film surface can attract and
embed dirt particles [100].
Sensitivity to Solvents
The sensitivity of acrylic emulsion paint films to organic solvents clearly limits a conservator’s choice of
cleaning techniques, consolidants, inpainting materials and options for varnishing and varnish-removal.
There is difficulty in removing embedded grime without disturbing the surface texture, colour and gloss.
Mechanical cleaning, such as with eraser crumbs or a molecular trap like Groomstick!® are sometimes
used before testing wet cleaning techniques [69,101] and have been investigated by Saulnier [102].
Solubility tests have been proposed as a simple form of analysis/identification preliminary to more complex
instrumental techniques [37,103]. Nielsen [103] discussed such solubility tests during forensic
investigations. Small quantities of unknown samples to be identified were exposed to solvents to view the
following phenomena: bleeding of organic pigments, swelling, dissolution of the film, and effervescence
from carbonate extenders and other additives. The reactions were compared with the reactions of control
samples for initial characterisation before further tests were conducted. The necessity of building a library
of identified standards is often stressed [37,103,22].
Sensitivity to Water
Even water or water-based cleaning methods can impact the paint surface. Acrylic emulsion films can
remain soluble in water up to a week and beyond after application. Upon drying, they become less soluble
in water [74,53,84,50,56]. However, it is widely known among conservators of modern paintings that
acrylic emulsion films remain sensitive to swelling by water. A recent study by Murray et al [101] tested
the effect of several water-based cleaning agents on the dimensions and mechanical properties of acrylic
emulsion paint films. Sample films of cobalt blue paint were submersed in water-based cleaning agents for
either one minute or one hour and then left to dry. One percent solutions of Orvus WA Paste and Aerosol
OT (both anionic surfactants), Triton X-100 (a non-ionic surfactant) and triammonium citrate (a chelating
agent with a pH of 7.2) were tested, all commonly used and visually effective cleaning agents. Immersion,
though not a conservation cleaning technique, is a repeatable test that may indicate the effect of multiple
cleanings on a painting and/or any residual cleaning agent left in the film, as well as results from disaster
An interesting conclusion was that samples immersed for one minute showed weakened mechanical
properties compared to those immersed for an hour. It was concluded that in one minute, only limited
penetration of the cleaning solution into the paint sample was possible, causing expansion of the outer
surface, but not the core, stressing the sample prior to mechanical testing. However, an hour’s immersion
allowed the solution to reach and react with all parts of the sample, leaving the sample uniform in condition
and in reaction to mechanical testing. After the minute-long immersions and subsequent drying, the sample
volumes had increased, mostly due to an increase in thickness, however, after the hour-long immersions the
samples returned to the original volume; indications were that after longer immersion times the thickness
and volume would decrease further.
Discussion about the conservation of these paintings has taken place almost since the introduction of
artists’ acrylic paint, however, there is clearly a lack of information on these materials and works of art that
is relevant to conservation. It is important to continue research and to share the information among
conservators, conservation scientists, artists’ materials manufacturers and artists. In terms of future
research, a fuller understanding in two broad areas is clearly needed: 1) the structure and components of
acrylic paints, in and of themselves, including the individual properties of additives and their interactions,
and 2), the effect of outside influences on the film, such as aging, abrasions, dirt pick-up and dirt location
within the film strata, wet and dry conservation cleaning techniques, as well as the paint film’s interaction
with other materials such as priming and varnish.
We would like to extend great appreciation to Dr. Alison Murray, Associate Professor, Queen’s University,
Kingston, Ontario, for her expert guidance and encouragement at the earliest stages in this research. We
would also like to thank Tracey Klein, paintings conservator, Edmonton, Alberta, Canada, for sharing her
informative survey results. Thanks also to Dr. Rene de la Rie, Jay Krueger, Dr. Suzanne Quillen Lomax
and Ross Merrill at the National Gallery of Art, Washington, DC; Benjamin Gavett, Braxton J. Tomsic and
Bill Berthel at Golden Artist Colors, Inc.; Dr. Frank Jones, Professor, Coatings Research Institute, College
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... They have been used as a medium for pigments [26][27][28][29][30], as a consolidant for waterlogged wood [31] and for basketry [32], for relining of canvas [3], as an adhesive for textiles [33,34] and wallpapers [35][36][37]. MC among other cellulose ethers have been added as additives (rheology modifiers, protective colloids) to starch adhesives and polymer dispersions [38][39][40][41][42][43] to improve working properties. Ethyl cellulose (EC) is hardly used in conservation [44] but is sold as film-forming agent for paints and for hot melt coating [45]. ...
... Ethyl cellulose (EC) is hardly used in conservation [44] but is sold as film-forming agent for paints and for hot melt coating [45]. Hydroxy ethyl cellulose (HEC) has also a limited use in conservation [44] and mainly occurs as emulsifier, stabilizer, thickener or protective colloid in dispersions [39,41,46,47]. Only few references document the single use of ethyl hydroxyethyl cellulose (EHEC), methyl hydroxyethyl cellulose (MHEC) and methyl hydroxypropyl cellulose (MHPC) in conservation. ...
Full-text available
Article downloadable Open Access from Heritage Science - Cellulose ethers, like methyl cellulose (MC) or hydroxypropyl cellulose (HPC), are widely used in conservation. They also occur as additives and rheology modifiers in various products like dispersions or gels. Do such products release harmful volatile organic compounds (VOC) during their accelerated aging? A mass testing series utilizing the Oddy test of 60 commercial cellulose ethers ranks the products in safe for permanent use (P, no corrosion), only for temporary use (T, slight corrosion), and unsuitable at all (F, heavy corrosion). Results show that 55% of the products passed the test whereas 33% are for temporary use as slight corrosion occurred on at least one metal coupon and only 11% failed the Oddy test. Raman measurements of the corrosion products identified oxides like massicot, litharge, cuprite, and tenorite among carbonates (hydrocerussite, plumbonacrite), and acetates like basic lead acetate, lead acetate tri-hydrate as well as lead formate as main phases. For example, commercial, industrial Klucel ® G (HPC) scored a T rating through slight corrosion on the lead coupon. Basic lead acetate among other phases indicates the presence of acetic acid. Additional measurements of the sample with thermal desorption GC-MS utilizing the BEMMA scheme confirm the high acetic acid outgassing and reveal the presence of a small amount of formaldehyde.
... Although some additives to polymers could represent a solution, sometimes these additives can leak out to the surrounding causing other problems [11][12][13]. Thus, a recent approach to reduce the leach of additives is by modifying the polymer, which can serve in the same manner as additives in enhancing mechanical properties, increasing flexibility, flame retardancy, and UV stability [14][15][16][17][18]. Different materials were used in polymers modification, such as aromatic compounds, phosphines, and metal complexes [19][20][21][22][23][24][25][26]. ...
Polymers are used in different applications that might be an issue for the environment. Thus, our strategy is to create a material that can be more sustainable and last longer in use. For this purpose, a new Schiff base was synthesized containing a triazole ring (L), which was introduced to a poly (vinyl chloride) (PVC) chain via substitution reaction. Copper chloride was then added to the previous compound to give the final product PVC-L-Cu. The films' resistivity to degradation under Ultraviolet (UV) light irradiation was investigated under accelerated conditions. Fourier-transform infrared (FTIR) spectroscopy, weight loss, and scanning electron microscopy (SEM) were used to follow the changes after exposure to UV light. The novel Schiff base enhanced the photostability of PVC polymer significantly in comparison to the pristine polymer.
... El PVA es, de todas las dispersiones vinílicas, la más utilizada con diferencia por su bajo coste. Químicamente, la estructura del acetato de polivinilo es compleja y ha ido evolucionado desde su irrupción en el mercado, de homopolímero a copolímero 8 (Jablonski: 2003). La elección de realizarlo como copolímero se debe a que, a lo largo del proceso, se le añaden compuestos como el PMMA 9 , que se evapora durante el secado, dejando la superficie de la pintura dura y brillante, pero no permite que la dispersión se disuelva correctamente en el agua. ...
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The present essay studies the work of one of the most important artists from Valencia in the contemporary scene over the last 50 years, Uiso Alemany Masip, and includes a thorough analysis of its pictorial technique and materials used in the work Hombre Alienado, from 1987, ceded for the study by the Museo de Arte Contemporáneo Vicente Aguilera Cerni, in Vilafamés, Castellón. Uiso Alemany´s work is a contemporary legacy of great value, not only artistic, but also scientific, since it uses materials which pose some challenges for its conservation, such as: polyvinyl acetate mixed with synthetic organic pigments, clay and pitch. This material, widely used in contemporary painting has suffered through all its story from terminological confusion, which hinders the bibliographic review. Thus, the investigation focuses primarily in the characterization of the PVA paint, using analytical techniques and archival research in order to draw the right information and acknowledge its chemical structure, film formation and polymerization process and behavior in combination with the artists plastic resources. Also, it´s degradation has been studied through accelerated ageing tests in a climatic chamber to determine which are the decisive environmental factors with the aim of stablishing a preventive conservation protocol to guarantee the conservation of this type of art works. It is presented then, a comprehensive characterization and an investigation that pretends to be useful, accurate and total, of a fundamental material for contemporary art and present, sometimes hidden or unidentified, in a lot of our museums.
... styrenated acrylic polymers tend to be cheaper than pure acrylics and are thought to be more susceptible to yellowing than pure acrylate containing equivalents. 15 it is noted that the non-styrenated acrylic varnishes applied to Man in Shower are older and remain less yellowed. how much this varnish has changed colour since the execution of the painting is not known, but the styrene component suggests that the yellowing may continue to develop slowly. ...
Contemporary artists embrace a wide range of paints for a myriad of reasons. Colour, gloss, cost and availability are key, as are drying time, adaptability and diluent type. Since the early 1960s, synthetic polymer and oil-containing paints have been used by contemporary artists to create a variety of surface and aesthetic effects. Many contemporary painted works are, however, beginning to show changes in appearance that are chemically complex and can prove challenging for conservation treatment. This chapter explores two key paint classes – synthetic polymer and oil-containing paints – through works drawn from the Tate collection by British artists David Hockney and Gary Hume, and the Indian artist Avinash Chandra. For each work, material choices have been explored via technical examination and scientific investigation and any changes noted have been considered within the context of current materials-based paint research, and information arising from artists' interviews, which offers the opportunity for reflection on how interactions with the artist can affect both the understanding and preservation of contemporary painted works of art.
... This way, the paint film coalesces. In addition, the natural cross-linking of the polymer could be achieved, increasing the hardness, resistance and mechanical properties of the paint film [23,24]. After curing the paint for 24 months, a sample set containing 15 samples of each type of paint was gradually aged under controlled accelerated ageing conditions, and subsequently analysed by FTIR-ATR. ...
In this work, the robustness and potential applicability of statistical age prediction models applied to the dating of different acrylic paints were studied. The FTIR-ATR analysis of three acrylic colours (Hansa yellow, phthalocyanine green and ultramarine blue) from two manufacturers (Liquitex® and Vallejo®) subjected to accelerated ageing was carried out. The acrylic paints were characterised and the modifications of their ATR spectra throughout ageing were studied. Predictive models developed with the Liquitex® brand containing phthalocyanine green pigment were then applied to other colour and brands of acrylic paints and their robustness and feasibility were studied based on calculated accuracy error values. The influence of the pigment on the ageing of the paint components, the type and quantity of additives present in the acrylic paint as well as the ageing conditions to which it was subjected were decisive in the short-term predictive model, which explains the low accuracy values obtained for all the acrylic paints analysed. However, the slower degradation processes taking place in the longer term and the stabilisation of the acrylic paints at higher stages of ageing made them fit successfully into the long-term model, obtaining an error of between 14 and 23%. Thus, the predictive statistical model is robust and feasible to be used for different colours of the same brand of acrylic paint as well as for acrylic paints of different brands that have been long-term aged under slightly different conditions of accelerated ageing. In conclusion, this methodology could be a promising tool in the field of dating contemporary artworks of a certain age.
... Though acrylic base paint media has been used for only 60-70 years [9][10][11][12] but there are numerous literatures presented degradation of art works using this synthetic material. Mecklenburg presented that at the low temperature acrylic paint film was stable without any damage due to their increasing of bulk material strength. ...
... Our third objective was to establish parameters for preparing samples specifically for modern and contemporary art materials. Water and solvents are used in traditional techniques of cross section preparation; however, the acrylic and mixed media materials used in modern and contemporary art are often water-and solvent-sensitive (Jablonski et al. 2018). ...
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The optimized method for preparing paint cross sections described here advances our understanding of the structure of multilayered modern and contemporary paintings. Conducted in micrometer scale with nondestructive characterization, this method of sample preparation preserves the morphological integrity of the paint layers, while achieving a high-quality surface suitable for imaging and inorganic mapping studies. The preparation begins by positioning the paint cross section face down on a restickable, double-sided acrylic adhesive dot affixed to a glass slide. A molded nylon ring is then placed around the sample and filled with Bio-Plastic resin. After curing, the sample is released from the ring. The paint layers are fully exposed because the dot does not bond with the cured resin. The sample requires minimal dry polishing for a high-quality surface because the cross section is not fully embedded in the resin; instead, the face of the cross section sits at the resin’s surface. These samples can be prepared in one day. In this study, we obtained data from a single paint sample from the twentieth century painting The Big Egg (1968) by Ed Clark, from the Smithsonian’s National Museum of African American History and Culture (NMAAHC). At least 15 layers were identified from one paint sample and were characterized using digital microscopy and SEM–EDS.
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Modern and contemporary art materials are generally prone to irreversible colour changes upon exposure to light and oxidizing agents. Graphene can be produced in thin large sheets, blocks ultraviolet light, and is impermeable to oxygen, moisture and corrosive agents; therefore, it has the potential to be used as a transparent layer for the protection of art objects in museums, during storage and transportation. Here we show that a single-layer or multilayer graphene veil, produced by chemical vapour deposition, can be deposited over artworks to protect them efficiently against colour fading, with a protection factor of up to 70%. We also show that this process is reversible since the graphene protective layer can be removed using a soft rubber eraser without causing any damage to the artwork. We have also explored a complementary contactless graphene-based route for colour protection that is based on the deposition of graphene on picture framing glass for use when the direct application of graphene is not feasible due to surface roughness or artwork fragility. Overall, the present results are a proof of concept of the potential use of graphene as an effective and removable protective advanced material to prevent colour fading in artworks.
Infrared spectroscopy has been used successfully in the characterization of several types of painting materials. Although most often employed with organic materials, the technique can also yield valuable structural information on many inorganic compounds. Several applications of infrared spectroscopy to inorganic pigments are reviewed, the theoretical bases for the spectra of these materials considered, and characteristic spectra presented. The materials discussed include chrome greens, green earths, and chromium oxide and viridian. Synthetic organic pigments can also be readily identified by infrared spectroscopy and one example (phthalocyanine blue) is discussed. All spectra were obtained from minute samples comparable in size to those often available from art objects, and were recorded using a Fourier transform IR spectrometer.
Each of us, artist, instructor, curator, and art conservator, share in common our ability and desire to learn from and build upon the past. In this regard there is no substitute for the original work of art itself. Few works of art have the chance of surviving intact without careful planning and judicious choice of materials and techniques by the artist.It is our responsibility to encourage the artist to use the best materials and techniques so that his work will endure the test of time physically as well as aesthetically. This is best accomplished by early training of the art student in sound principles of craftsmanship.“Continuing education” seminars should be organized periodically in various geographic locations for the practicing artist, as a refresher course and to familiarize the artist with current developments in materials and the craft of painting.
Emulsion paints may enhance mold growth since they contain organic components that may serve as a nutrition source for the fungi. The objective of the present work was to investigate the effect of the paint's microstructure and porosity, as related to its pigment volume concentration, on the resistance to mold growth. Tests, including porosimetry, electron-microscopy, and accelerated mold growth, were performed in an environmental chamber on a series of polyvinylacetate and acrylic emulsion paints with various pigment volume concentrations. Results show that the very porous paints of both kinds are much more prone to mold growth than are those with pigment volume concentrations below or around the critical value.
The prior art on particle coalescence and film formation of latex particles is reviewed in the first part of this chapter. In the latter part, the particle coalescence of step-growth oligomer dispersions is discussed. The synthesis of the latter type is discussed in chapter 1, and their application properties are discussed in chapters 7 and 8. The coalescence of water-borne epoxies is discussed in one of the sections in Chapter 5. Peripheral to this chapter, the phenomena of dispersion coalescence is discussed from a uniquely different perspectives for alkyd dispersions in chapter 10 and for high clay content, paper coatings in chapter 13. The reader also is referred to chapter 14 where the importance of the drying process on film formation properties, in areas outside consumer architectural coatings, is discussed.
Because the properties of latex films may be inherently influenced by the surface activity of surfactants, determination of surfactant distribution throughout the latex film is an essential factor in many film properties. Sodium dioctyl sulpho-succinate/ethyl acrylate/methacrylic acid (SDOSS/EA/MAA) latex films were analysed at both the film-air and film-substrate interfaces by photoacoustic (PA) and attenuated total reflectance (ATR) FTi.r. spectroscopy. It was found that the surfactant distribution at the interfaces depends upon the water flux out of the film in the early stages of the film formation and the surface tension of a substrate.