Written by:
adamc
The Science of Acrylic Paint

Acrylic polymers began life early in the 20th century as replacements for glass and for use in textiles, far before they were thought of for use in artistic endeavors. Acrylic dispersions were eventually used in house paints until exploration in the 50’s and 60’s led to the creation of artist grade acrylic paints. The synthetic resin binder emulsion of extremely fine particles was dispersed in water, then milled with pigments, as moisture evaporates from the applied paint only the acrylic resin and pigment remain. The unique properties of acrylic resin combined with many of the same pigments used in oil and watercolors created a medium that dried quickly, was easy to clean up and could be employed effectively on a variety of surfaces.
The binder used in acrylic polymers dries rapidly and forms a clear film that does not yellow, is flexible and very adhesive. The solution behaves much like oil paint and can be manipulated to create similar effects, but it can also be watered down and used in the same way as watercolors. The main differences are the brushing quality (oils are more viscous and are workable longer) and permanence (watercolors can be lifted away to a greater extent).
(Reference material: The Painter’s Handbook - 1993 Mark David Gottsegan & The New Artist’s Manual - 2005 Simon Jennings
Acrylic as Water Medium

One of the major advantages of acrylic paint is it’s ability to be employed in a number of ways, opaquely right out of the tube, thinned to a transparent glaze with a medium or diluted with water to be used similarly to watercolors. It can even be thinned to the point that it can be used in an airbrush. This month in the Learning Center we’ll show you how to use your acrylics to mimic the look of a watercolor paint. Diluted acrylics will have more permanence in mixed media applications than traditional watercolors and they can also be used as a wet medium on canvas (watercolor paint has a tendency to bead up on primed canvas).
It’s a pretty simple process, the more water you add the lighter your color will be:

Here you can see we’ve made some nice puddles of acrylic color that can now be used to mimic watercolor techniques.

Here a sheet of watercolor paper has been dampened to employ a traditional wet on wet watercolor technique.

The damp paper will help keep the acrylic workable and you can continue to add wet on wet layers.
We allowed these layers to dry then worked in detail layers with a very thin but highly pigmented solution of acrylic and water. The final gives the look of a watercolor painting, but since it is acrylic based, the image is completely waterproof, meaning additional layers of wet or dry media can be added on top without affecting the original painting in any way.
Another great use for a watery acrylic mixture is a fast drying solution to toning a canvas or panel for painting. This ground (in our case, a blend of burnt sienna and ultramarine) will be ready to paint on in as little as ten minutes and it’s safe and completely archival to apply oil paint over the acrylic ground.
So take advantage of the flexibility of acrylic paint, experiment with layers and building up watercolor-like washes or try it out to quickly tone a canvas or panel for your next oil painting.