As with any surface around the home, office, or especially, in a public
place, paintings become a depository for airborne dust. They can also
get touched occasionally, either inadvertently or purposefully, and may
become soiled from the contact. Acrylic paintings have unique attributes
that affect their propensity for attracting and retaining dirt and grime.
One theory is that they are prone to carrying a static charge, which results
in greater dust attraction and retention. Regardless of whether this characteristic
substantially affects dust attraction, based on our observations of acrylic
paint and conversations with conservators, we know that the thermoplastic
nature of the paint film can result in significant adhesion of particles
to the surface.
"Thermoplastic" means that the relative hardness and flexibility
of the polymer are influenced by changes in temperature. As temperatures
increase, acrylic becomes softer, more flexible and may become tacky.
As this happens, any debris present can become adhered to the surface
and will subsequently require relatively aggressive methods for removal.
While the manufacturer of acrylic paint can choose harder polymers that
are less prone to this problem, there are trade-offs associated with their
use. The principal virtues of acrylic paints are their inherent film flexibility
and lack of brittleness. Using harder acrylic polymers would result in
a painting being more susceptible to cracking from impact or movement
during shipping as the result of raising the glass transition temperature
(GTT), the point at which the film will snap like glass instead of bending
as plastic is expected to. A higher GTT increases the risk of permanent
damage to a painting from mishandling. GOLDEN Acrylics are formulated
to optimize flexibility of the paint film and to maintain a reasonably
low GTT. However, this does mean that unprotected paintings are at greater
risk of requiring more aggressive cleaning practices.
Characteristics of a paintings construction also affect its tendency
to retain foreign material and its subsequent ease of cleaning. These
should be considered when choosing materials to execute a work and when
deciding on display locations and conditions. For example, use of acrylic
paint allows the artist to build incredible impasto surfaces that dry
quickly, without deforming. The resulting terrain of this type of surface
contains numerous horizontal planes which act as shelves for dust to land
on and become embedded into over time. The surface may also contain concave
areas and hollows in which debris can collect. Compounding this characteristic
is that these areas can be extremely difficult to clean.
On a more microscopic level, the acrylic paint film is relatively porous,
caused by tiny voids left as the water evaporates during the drying process
and protrusion of solids near the surface of the film as it shrinks during
drying. The subtle texture that results provides a surface that is both
easier to soil and more difficult to clean, similar to the difference
that might be noticed in gloss vs. satin interior house paints. This characteristic
is accentuated with certain specialty products. For example, GOLDEN Pastel
Ground is designed to abrade and retain soft materials that contact it,
while GOLDEN Absorbent Ground is especially effective at drawing stains
into the surface. Therefore, left unprotected, both are at higher risk
of becoming soiled and would be more difficult to clean than regular GOLDEN
Another characteristic of acrylic paint that provides both a benefit
and reason for caution is its ability to function as an adhesive, particularly
during the final stages of drying. This property is effectively used by
collage artists wanting an archival means of assembling a work because
the acrylic does not become brittle with age, remain water resoluble or
discolor like many traditional glues. However, this property may result
in paintings becoming permanently marred if foreign material is allowed
to touch the surface during the final stages of drying, as might happen
if dust from sanding is in the air of a studio.
The ability of the binder to function as a stand alone medium for painting,
as with GOLDEN Gels and Mediums, adds another dimension to the visual
effect possible with acrylic. If the intent is to look through a layer
of relatively clear media, a dirty surface is quite distracting. Too often,
a clear acrylic dispersion media (i.e., GOLDEN Polymer Medium) is selected
as a final topcoat in lieu of a removable varnish. Used as such, there
is the risk that once dirty, there is no assurance that it can be effectively
cleaned, especially without affecting light transmittance of the film
due to potential physical abrasion from the cleaning process.
Overuse of additives to achieve performance variations in acrylic paints,
such as GOLDEN Retarder to slow drying or Flow Release to enhance staining,
can also affect dirt retention properties of the paint film. Retarder
does increase the open time, but will also lengthen that period when the
paint is no longer workable, yet is still not fully dry. During this time,
the paint film is far more susceptible to retaining airborne contaminants
that contact it. Similarly, Acrylic Flow Release used in excess can result
in a paint film that remains extremely tacky for a long period of time.
Knowing why acrylic paintings may eventually require cleaning is helpful
because this knowledge can be used to make choices that will aid in avoiding
or postponing the cleaning process, which is the first level in the hierarchy
of conservation practice, i.e., prevent the need for intervention.
Why Minimize the Need for Cleaning
Every time a painting is touched, it is at risk of being changed or
damaged on some level. In taking the long view that art materials should
be manufactured to be as archival or long lasting as possible, the advice
offered herein for cleaning practices follows a similar theme. The fewer
times a painting is cleaned, the less chance there is for permanent damage
to occur. Sometimes these effects are almost microscopic, such as minute
scratches that may occur if dust or an abrasive cloth is wiped across
the surface or the concern that use of mild cleaning agents will remove
small amounts of soluble components of the paint. At the other extreme
is the possibility of permanent visual changes that could result from
the wrong choice of cleaning method by an untrained individual, such as
a "tide line" appearing on a stain-painted canvas because a
wet cleaning method was used, or burnishing of a matte surface resulting
from trying to wipe away dirt. Worse yet, for example, would be if a fragile
paint film is aggressively cleaned and large, visible portions of paint
are accidentally removed from the support.
Regardless of the amount of change, in the context of thinking that art
should be capable of lasting forever, any change or potential for change
to the piece through cleaning conflicts with this end. For this reason,
cleaning of paintings by professionals in fine art conservation is the
best approach to maximize longevity. They employ a tiered approach to
cleaning that starts with the least intervention possible and progressively
becomes more aggressive as needed. However, there are upper bounds of
intervention dictated by the risk of the cleaning activity permanently
affecting the painting, balanced against the anticipated incremental gain
A General Approach to Cleaning Acrylic Paintings
In our conversations with people in the field of art conservation,
we often ask "How do you clean acrylic paintings?" Although
the most common answer is "with great difficulty," were
looking for something more concrete. From these conversations and the
general lack of material on the subject in conservation publications and
symposia, it is our impression that there remains room for further research
in this area. However, there are commonalties in the approach to cleaning
paintings that are worth describing. The following series of steps is
a compilation of approaches of several conservators with whom we talked.
Because of the lack of definitive research in this area, some of the ideas
presented here should be considered experimental and may be debatable.
- At the first evaluation and at each subsequent step, the question
must be asked, "Is the anticipated intervention necessary?"
Current ethics in conservation prescribe a minimalist approach to the
treatment of paintings. This is due to the recognition of irreversible
changes that have occurred to works of art during the infancy and adolescence
of the conservation profession. A simple treatment involving minimal
risk and contact with the painting may be easily warranted, while an
aggressive wet-cleaning method without assured outcome is cause for
- A careful evaluation of the surface is performed to determine if
the piece can withstand whatever plan of treatment is designed. Is the
surface stable? Are there areas of poor adhesion, weakly bound paints
or fragile areas? What is the surface sheen and how will it be affected?
Is the piece varnished, and if so, can the varnish be safely removed?
It is extremely useful to know the materials used by the artist in the
painting. For this reason it is helpful for the artist to provide documentation
with the painting that details support preparation, type of media, isolation
coat and varnish used. A copy of this record should also be retained
by the artist.
- The nature of what is being removed is determined. Is it dirt or
grime on the surface? Is it dirt embedded, or both?
- Realize that any surface contact should be minimized, so initial cleaning
attempts should be designed accordingly. One method is to use compressed
air to blow away surface dust. Another technique involves using a soft
sable brush to lightly brush the surface in order to dislodge dust while
holding a vacuum source, off the surface, to capture and remove debris.
- If the dirt is embedded and vacuuming doesnt remove all of
it, the next level of intervention involves dry cleaning methods (not
to be confused with solvent washing of clothing) with more aggressive
surface contact. Materials described as hydrophobic sponges and molecular
traps that are able to overcome the physical adhesion between the dirt
and paint film, without imparting their own residue, are used. Erasers
and similar materials that may fill in the pores of the paint should
not be used. It may be possible to use tape to lift dirt from a painting,
as long as there is assurance it will not leave a residue. Whenever
a cleaning method is used involving surface contact, it is advised that
paintings on flexible supports be suitably backed to minimize surface
deflection and equalize working resistance.
- As a last resort, a cleaning method utilizing moisture may be required.
Generally, this applies only to stable, undamaged surfaces. Potential
dangers of such an approach are that liquid cleaning may actually drive
dirt deeper and make matters worse or can create tide lines in the support,
which result from solublized material concentrating at the wet edge.
It is also theorized that wet cleaning at the surface will create rheological
differences in the paint film.
An effective and time tested cleaning technique is euphemistically referred
to as "enzymatic cleaning". It involves moistening a clean
cotton swab in the mouth and rolling it across the paintings surface.
Saliva is warm and contains enzymes which act upon both lipids and proteins,
two common components of "dirt". It is important to note that
the correct procedure is to roll the swab across the surface, as opposed
to rubbing it, which could cause abrasion. The process must be extremely
gentle and it is important to keep the moisture on the surface to a
minimum. The procedure is started by testing in a small area of the
painting judged to be least noticeable. At each step of the treatment,
the painting is carefully examined for changes in gloss and color pickup
on the swab. Sometimes it is necessary to work through "Japanese
Tissue", which allows the dirt and moisture to wick away from the
painting. Deionized water may also be an appropriate choice for moist
As an aside to the procedure of working with a cotton swab in small
areas, we have heard concerns that this may lead to the surface appearing
mottled. Presumably, this would result from slight differences in factors
such as the amount of moisture or pressure used, or the amount of dirt
- The final step (and the first step) is to evaluate the conditions
which led to the need for treatment. Can a cleaner environment be found?
Should a removable varnish be applied?
- If aesthetically appropriate, apply an isolation coat and varnish
to acrylic paintings to facilitate ease of cleaning. Use a removable
varnish such as GOLDEN Polymer Varnish or MSA Varnish. The removable
varnish layer allows the paintings surface to be cleaned at a
much lower risk. If it becomes scratched or if dirt does become permanently
embedded in this layer, the varnish layer can be sacrificed by removing
it (consult GOLDEN Technical Data Sheets for Polymer Varnish and MSA
Varnish for removal techniques), and a fresh layer of varnish can be
applied to restore the painting to its original appearance.
- Practice proactive prevention. Display paintings in the cleanest,
lowest traffic areas possible. Vacuum or mop these areas, rather than
sweeping, to minimize airborne dusts.
- Minimize exposure of acrylics to elevated temperature, especially
in combination with dusty conditions. Such areas may be near hot air
inlets, in direct sunlight or attics.
- Minimize frequency of direct contact, such as dusting of unprotected
acrylic surfaces. Instead, use compressed air.
- Seek out professional services as appropriate for the piece and conditions.
By virtue of training, experience, tools and techniques, the risk of
damage to the painting will be much less if it is cleaned by a reputable
professional in the field of fine art conservation.
- Recognizing the need for specific techniques for protecting as well
as cleaning acrylic paintings, we invite response from conservation
professionals who wish to share their experiences.
The following people are thanked and acknowledged for independently sharing
information for this article.
WestLake Conservators, Ltd.
Any errors or omissions are the sole responsibility of the author.
GOLDEN Artist Colors, Inc.
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