By Bill Berthel
This article is an attempt to establish a common language and an understanding
of acrylic dispersion grounds, the attributes of the grounds and how those
attributes function within the painting. This article will conclude with a
very needed but mostly ignored effort to understand the development and
necessity for a quality standard for grounds.
Contemporary materials referred to as “gesso” or “acrylic
gesso” could be more accurately described as “Acrylic Dispersion
Grounds”. Acrylic dispersions are the binders most commonly used in
artist acrylics. Mistakenly called “Acrylic Emulsions” by many
people for many years, acrylic dispersions are much more widely used in
artist materials than emulsions. For technical clarity and use in this
article we will only use the descriptor “gesso” to describe
the very traditional, chalk-filled, hide glue grounds.
The following definition from “The Artist’s Handbook”,
Ralph Mayer Fifth Edition Revised and Updated, serves as an
excellent reference to describe “gesso”.
Gesso is a viscous or liquid material applied as a coating to surfaces
in order to give them the correct properties for receiving painting,
gilding or other decoration.
Mayer goes on to describe the general makeup of gesso:
It is made by mixing an inert white pigment such as chalk, whiting or
slaked plaster of Paris with an aqueous binder such as a solution
of (animal protein) glue, gelatin or casein.
For this article, I will call the contemporary material widely used by
artists to prime and prepare most substrates as an “Acrylic
Dispersion Ground”. This, might be confusing at first, as
nearly all manufacturers, including Golden Artist Colors have
called their products “Gesso” or “Acrylic
For clarity: Gesso is (animal protein) glue, gelatin or casein
based while Acrylic Dispersion Grounds are those grounds
made with acrylic polymer.
We also commonly refer to the process as, “To gesso a canvas.
” This description will be technically confusing when
we need to discuss Acrylic Dispersion Grounds as
“gessoing”. “Gessoing” more strongly
references the chalk-filled hide glue material. For our
new common language, we may consider the idea of
“priming” and the use of that word and
action to describe what artists do with Acrylic
Dispersion Grounds to prepare a substrate. Priming is the
action of coating a substrate for additional coatings and
finishes. Priming is a much more fitting description and so
we’ll utilize that term for this article and in future
references to what we formally knew as “gessoing”
It needs to be understood however, that the market cannot make changes
to its language and communication very quickly. Not even Golden
Artist Colors can change rapidly enough to avoid confusion and
some level of conflicting information in the marketplace. We
will continue to see labels and literature for a long time to
come that will reference Acrylic Dispersion Grounds as Gesso.
We now have an opportunity to initiate that change within this
conversation so that we may begin creating more clarity and
technical accuracy in our language.
The Purpose of a Ground
Nearly all substrates such as canvas, linen, paper, wood and
other panels require additional preparation before painting.
The preparation differs, depending on the desired aesthetics of
the work, the painting media being used and the qualities of the
particular substrate itself. Generally speaking, the need to
protect substrates from waterborne paint systems is much simpler
compared to the technical requirements when using solvent or
oil systems. Water migrating from sizes, primers and paints can
affect some substrates, causing such problems as buckling papers
and shrinking textiles. However, the impact on longevity
compared to the need to protect canvas from oil differs.
Most substrates and thus artwork, can
benefit from proper size and ground preparation if the aesthetics
of the piece allows.
Size and ground layers are employed to prepare substrates so that they
are protected, more stable and consistent for accepting paint and
other media. Although this article will not address all of the
attributes of sizes, it is important to mention that sizes are
typically applied directly to the substrate. “A size sinks
into the support’s surface without forming a separate layer,
whereas a ground is a distinct layer that gives the paint a toothy
coating to grip and makes the support more evenly absorbent,”
from“The Painter’s Handbook”, by Mark
Paintings are typically comprised of multiple media or materials. Not to
confuse this idea with “multi-media art” or
“mixed-media art” however most paintings should be
thought of as composites of diverse materials. Assuming a “
traditional” painting format of a stretched textile such as
cotton canvas or linen and putting aside the stretcher bars as one
material of the whole, we must consider the following relationships:
the textile and size have an intimate relationship, forming the very
foundation for a ground. The size and ground are the next layers in
sequence and must be compatible both physically and chemically. Next
the colored paint layers, are the most obvious portions of the painting,
and also serve to support the structure of the painting. And finally,
the protective coatings such as an isolation coat and a varnish when
employed need to be considered as an integral part of the painting. When
considering the complexities of such combinations, it is important
to understand the relationships between each material, how they are
applied, their movement over time and ageing properties of each to
assure the longevity and stability of the painting.
Attributes of Acrylic Dispersion Grounds
Perhaps, originally, the intent of making “acrylic gesso”
was to offer something very similar to a traditional gesso. It seems
reasonable that the need to emulate the properties of gesso for oil
and acrylic painters began as a very specific focus that naturally
broadened due to the immense diversity available in acrylics. A new
way to think about primers and gesso is that a gesso for oil paint
mindset need not apply to acrylics. The attributes afforded by acrylics
started to address many of the shortcomings of traditional gesso such as
its brittle nature, limitations to stiff or rigid substrates, the
inconvenience of mixing and preparing the gesso and the ease of
application with minimal technical requirements.
As a category of materials, acrylics provide many diverse attributes. There may
be no other artist material that has such diverse possibilities. These
variables allow formulators to create many unique products for the artist
with highly specialized performance attributes. Acrylics may range from
very soft and flexible to very hard and brittle, easily cracking when flexed.
Some acrylics formulate well with a wide range of pigments and additives
while others have limitations. We’ll limit our discussion here to
the attributes of acrylics most related to grounds. This limited
discussion is in no way complete as there are many alternative uses
for Acrylic Dispersion Grounds and many acrylic products that can be
used as a ground.
Pigment Volume Concentration (PVC)
An acrylic’s capacity to carry pigment and filler solids is technically
referred to as pigment volume concentration (PVC). As a category, acrylics
provide a wide range of PVC. Some acrylics have higher PVC tolerances than
others. How much and what type of solids are loaded into the acrylic directly
influences attributes like tooth, sheen, opacity, color and flexibility.
While the artist will likely never think about PVC as an attribute, it is
an important concept to understand related to other binders such as oil
and alkyds, which carry solids differently, resulting in different
attributes and performance when compared to acrylics.
Cross Hatch Adhesion Test
Right: Oil paint is easily removed from a smooth ground.
Left: Oil paint is adhered well to a toothy ground.
Physical adhesion is largely accomplished through a “lock and key”
mechanism commonly referred to as “tooth”. A toothy surface
has adequate micro-texture to allow a subsequent coating to physically
conform to that texture. When the coating is able to conform and create
an intimate interface with the toothy ground, good mechanical adhesion
is accomplished. In contrast, a very smooth and glossy surface such as
glass, which has no tooth and provides minimal physical adhesion
unless sandblasted or etched. Tooth of a ground should be uniform
and consistent, as to not interfere with the artist’s end
When employing flexible substrates, flexibility of the painting
media and supporting materials are likely necessary to avoid such
defects as cracking, and possibly delaminating adhesion failure of
the paint. Acrylic Dispersion Grounds are typically formulated with
relatively flexible acrylic polymers so that they can maintain some
level of the flexibility of the substrate and not crack themselves.
This flexibility of the ground is well suited and generally matches
the physical dynamics of acrylic paints and mediums on cotton canvas
duck. Flexibility of the ground is important for stretching or
re-stretching already primed/painted substrates. It must be mentioned
that there are some concerns about the flexibility of acrylic grounds
for use with oil paints, especially as the oil paint films become harder
and more brittle with time. The acrylic ground maintains its flexibility
over time rather well compared to linseed oil primers and paints. These
materials may not provide the support a less flexible oil paint requires
without a size or multiple coats of acrylic dispersion ground to stiffen
The color of a ground is important aesthetically to both the artist and the
artwork. A consistently colored ground is important so that there is minimal
influence on color perception and color mixing while painting. The color
(typically white) creates a visual reference point for the artist that
could otherwise confuse or distract accurate color usage. Equally
important, having an equitable colored surface creates uniformity in
the aesthetic affects of the final piece. Acrylic Dispersion Grounds
can be easily tinted with acrylic color, presenting the artist more
opportunities. A less obvious feature of a white ground is that it is
typically more color stable than the substrate. Many substrates,
especially those containing cellulose such as vegetation fiber
(cotton and linen) or wood and paper have tendencies to yellow and
discolor over time. Grounds protect this discoloration from affecting
the aesthetics of the artwork.
Acrylic Dispersion Grounds, like all grounds are formulated to provide enough
absorption to allow some level of penetration of paint to promote adhesion
as well as allowing the artist to begin her process with washes if so
desired. Absorption and adhesion are related because the physical
penetration of the binder-rich acrylic paint into the substrate or
ground provides good anchoring of the acrylic. More importantly, when
using oil paints, the absorption needs to allow enough linseed oil to
penetrate without starving the paint layers of the vital binding oil.
When employing washes, standard grounds provide enough absorption to
allow a fair amount of wash and layering. However, the level of
absorption a ground provides can be adjusted through formulation.
An alternative ground such as GOLDEN Absorbent Ground can dramatically
increase the staining of a wash into the substrate.
Linseed oil absorption into ground layer facilitates
adhesion to an acrylic gesso or ground.
Support Induced Discoloration
Abbreviated as SID, water miscible components of the substrate may be wet out
by the water in grounds or paint layers, becoming transferred and
lodged in the ground and paint during the drying process. Drying of
acrylics is largely due to evaporation of water and other volatiles.
The wicking action that occurs during evaporation can transfer these
water miscible components from the substrate into the paint, resulting
in a discolored, typically yellow or tan cast of color.
SID is most noticeable with white and
very light colors as well as with clear gels and mediums.
SID: Support Induced Discoloration. Discolored water
miscible impurities migrate from the support through the
ground and become trapped in the acrylic film as seen
in half of this image. The other half has a ground / size
combination that blocks the migration.
Grounds may or may not block SID from occurring. Many grounds do not. The use
of a size such as GAC 100 will help reduce the affects of SID. GOLDEN
Technical Support suggests the use of GAC 100 as a size for cotton and
wood substrates followed by a minimum of three coats of White Gesso. If
the substrate is suspected of being highly concentrated with water
miscible components such as questionable grades of cotton duck canvas,
hardboards and certain species of wood, additional coats are recommended.
It is also possible to pre-wash cotton or linen to dramatically reduce
the yellowing affects of SID.
Oil seen here staining right through the back
of a poorly prepared dispersion ground.
Related to the ability of an Acrylic Dispersion Ground to absorb oil, it must not
allow oil to fully penetrate through to the substrate. This is especially
important when painting on canvas as the acidity of the linseed oil increases
as it oxidizes and will “burn” the cotton duck canvas. Most grounds
do not block oil completely and require the use of a size to further protect
the cotton duck canvas. The same recommendations for SID apply to oil
Alternative Grounds: Beyond "Gesso"
Because acrylics are so adaptable and diverse, there are many opportunities to utilize
products not commonly thought of as a ground, as a ground. Generally, artist
acrylics are flexible and adhere very well to one another, practically
eliminating any rules or limitations often experienced with other painting
media. Gels, Molding Pastes, Mediums and Colors such as Heavy Body, Fluid,
Matte, and High Load Acrylics can be and often are, used as grounds.
There are also specially formulated acrylic grounds to consider. Each one provides
a certain property that may be valuable for some artwork or experimentation
in a new area of application.
Originally formulated to mimic the absorbency of watercolor paper,
Absorbent Ground has been used in many unique applications. The special fillers
in this formula are highly absorbent and will lend to watercolor-like effects
with acrylic paints, watercolors and other dilute, thin washes. This ground
requires the use of a primed substrate for adequate adhesion.
Acrylic Ground for Pastels
Designed and formulated to allow the artist to transform most
substrates into pastel paper-like surfaces, Acrylic Ground for Pastels is
a very unique product. Special functional fillers chosen for optimized
particle size and shape and formulated with the appropriate solids
loading, allows this ground to produce a surface suitable for pastel,
colored pencil, paint and other drawing media.
Translucent Grounds are still considered “experimental,
” meaning they are only available from the GOLDEN Custom Lab. These
grounds tend to be good drawing and painting grounds. Golden Artist Colors
has optimized the use of specialized functional fillers in a ground formula
allowing very translucent, practically clear, toothy grounds that accept
painting and drawing media very well. These grounds hold pencil, charcoal,
pastel and paint allowing distinction of line and blendability of the media.
Quality Standard Development
It is obvious that given the importance of sizes and grounds to the overall
stability and success of a painting one would think that there are already
standards that define the very specific relationships and performance
attributes of these materials. The ASTM D01-57, subcommittee for Artists
Paints and Related Material, have developed several standards over the last
30 years, many of which have become commonplace within our industry. The
Artists Materials ASTM subcommittees are composed of manufacturers,
consumers, educators, students and special interest participants such
as scientists and other experts in various markets and disciplines. This
dynamic mix of participants helps to facilitate collaboration and assures
the development of valuable standards that serve all parties involved.
One would be hard-pressed to buy a tube of paint without seeing the ASTM
Lightfast Standard, or D4236, the Safety Standard for Chronic Toxicity.
These standards have been developed to assure artists of at least a common
language for these materials and a minimum level of performance.
These documents prescribe test methods to assure desired quality attributes
are achieved for a particular product or family of products. The American
Standardization of Tests and Materials International (ASTM) is a standard
development and writing organization in which Golden Artist Colors
Random surface quality due to
inconsistant particle size of pigment solids.
Consistent surface and tooth of a well
made acrylic gesso.
It is critical to understand that there are currently no quality standards in
place for gessos or grounds. There are architectural primer standards
that are used for reference while developing an artist ground standard,
however, for manufacturers of artist materials, there are no specific
guidelines or standards. The fact that such a foundational product does
not have a quality standard does a disservice to artists depending upon
these materials to perform. Through the ASTM D01.57 “Artist Paints
and Related Materials” Subcommittee, GOLDEN is specifically
interested, and has been leading the efforts in writing the first
quality standard for Acrylic Dispersion Grounds. It must be recognized
that GOLDEN does this work with tremendous collaboration from colleagues
and competitors within the subcommittee.
The focus of the Acrylic Dispersion Ground quality standard is to identify and
assure the most critical attributes for a ground are met. The attributes
mentioned earlier are all considered in the testing and development of a
quality method. Standard development is a process, which takes time. The
testing and work is carefully conducted and repeated to assure purposeful
accuracy. The subcommittee is required to vote for ultimate approval of the
standard document. Therefore, the scientific approach of testing and
publishing the work for critique is essential. The design of the experiments
is proactively agreed upon at the subcommittee level, reaching consensus for
experimentation and expected results. As work is presented, ideas and
perspectives are shared and thus the process develops over time.
Currently, a fairly comprehensive quality survey of commonly available
“gessos” has been conducted. This survey has uncovered
a large amount of variability in several attributes such as tooth,
sheen and viscosity. While quality standards do not need to make all
offerings in the market identical, significant variations may or may
not be an indicator of highly variable performance and quality. There are
likely reasons and needs to have grounds as thin as heavy cream and as thick
as heavy pastes. However, knowing that the mechanical adhesion of paint relies
on the tooth of the ground, identifying and standardizing a range for tooth
may be necessary.
With the common language agreed upon and understood, we can move not only the
current products and applications forward for improved longevity and
quality, we can continue the quest toward assuring these improvements
through robust standards. As newer grounds and more and more pre-primed
canvases come onto the marketplace, it is more critical than ever that the
arts community supports and demands these standards. It is true that
standardization development is a slow and careful process, but it is one
worth the investment in time and resources in order to serve the artist
and our shared legacy. Your painting success rests on
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