Oil painting is the process of painting with pigments that are bound with a medium of drying oil (hence the ‘oil-based’ appellation). The binder most commonly used is linseed oil, but poppy seed oil, walnut oil or safflower oil can also be used, with varying results. Different oils confer various properties to the oil paint, such as less yellowing or different drying times, or a different sheen. A basic rule of oil paint is ‘fat over lean’. This means that each additional layer of paint should contain more oil than the layer below to allow proper dying. If this rule is not followed, the final painting will crack and peel. Oil paints may require the use of solvents such as mineral spirits or turpentine to thin the paint and clean up. Recently however, some water miscible oil paints have been developed for artist’s use.
Acrylic painting is the process of painting with pigments that are bound by an an emulsion of water and acrylic polymer. Acrylic artist paints may be thinned with water and used as washes in the manner of watercolor paints, but the washes are not re-hydratable once dry. The artist can mix media with their paints, and use topcoats or varnishes to alter or unify sheen if desired.
The main difference between the two media is the drying time: Oil paints remain wet longer than acrylic paints, enabling the artist to change the color, texture of form of the figure. At times, the painter might even remove an entire layer of paint and begin anew. But it also makes it impossible to work fast. When using acrylic painting, it is possible to use acrylic retarders to slow the evaporation rate of the water. These acrylic retarders are generally glycol or glycerin based.
Another difference is that oil paint has a higher pigment load than acrylic paint. Besides, not all pigments in oil are available in acrylic. But acrylic paints, unlike oil, may also be fluorescent.
Finally, acrylic paint offers much more versatility and lends itself well to decorative arts. Acrylics can be used in Mixed Media (see the ‘mixed media’ tab on our website), and allows the use of pastel, charcoal, pen, etc. on top of the dried acrylic painted surface. Mixing other bodies into the acrylic is possible –sand, rice, even pasta or fabrics may be incorporated in the artwork.