About Acrylic
Paint
Acrylic paint consists of pigment bound in an acrylic
emulsion (oil paint is pigment bound in a drying oil, i.e.
linseed oil). The emulsion consists of particles of polymer suspended in water. When the water evaporates, acrylics dry to a flexible
and water-resistant film. This film is a type of plastic.
Oil paint dries to a tough, leathery film through oxidation, which is
a much slower process. (See About Oil Paint.)
Hence, you don’t have the “open time” in acrylics
that you have in oil paint.
With this in mind, perhaps the best approach is to utilize acrylics
rapid drying time to your advantage. Wet-into-wet techniques still work
best with oil paint. Acrylics, however, permit you to work in multiple
layers within a short period of time. The wealth of
mediums available to the acrylic painter allow for effects
ranging from thin washes a la watercolor to
heavy impasto techniques. The inherent “glueness”
of acrylic also makes it an excellent adhesive for
collage and mixed media. In addition, acrylic paint adheres well to
any porous, non-oily surface. (Oil paint can be applied over an acrylic,
but an acrylic cannot be painted over oil). Thus, paper, cardboard,
wood and canvas make excellent painting surfaces with minimal
preparation.
COLORS
Acrylic paints come in a range of color equal to the range available
to the oil painter and watercolorist. (The sole exceptions are viridian and lead white, which the acrylic emulsion can’t
successfully absorb). Acrylics also carry a slightly lower pigment load
than oil paints. This explains why a tube of cobalt blue acrylic paint
costs less than a tube of cobalt blue oil paint.
PRIMERS
In oil painting, the primary purposes of priming the painting surface
are to make the support more receptive to the paint and to protect the
support (canvas, paper) from the destructive acids that are in the oil
paint film. Because acrylic paints don’t contain destructive acids
the reasons to prime a surface are to give the painter
some control over the quality of surface to be painted on and provide
some protection to the paint film from the possible
destructive acids in the support itself (primarily in the case of wood or masonite).
Acrylic primers, generally labeled gesso, are comprised
of the acrylic emulsion used in the paints, with the addition of white
and other materials that provide a “tooth”
for the paint film to grab hold of. Some manufacturers make a black
gesso for artists who wish to paint from dark to light.
Acrylic Mediums
Mediums available to the acrylic painter range in consistency
from pourable to moldable. Gel mediums maintain or increase body to
the paint while fluid mediums promote flowing and leveling. Pumice
gels and molding paste add texture. Mediums
may be used to create glazes and transparencies,
change finishes and act as an adhesive for collages. The key here is
to experiment. While acrylic can be thinned with water, it isn’t
recommended to overthin with water. This acts much the same way as overthinning
a glue, or using turpentine as your sole medium in oil painting. Extend
or dilute your paint using mediums.
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