Since they were first introduced in the 1950’s, acrylic paints have come a long way on several levels such as the quality of the product and the level of acceptance with artists and in the art world. At one time people only used acrylic paints if they had developed a sensitivity to the mineral spirits or turpentine used to thin oil paints and clean up toolused in oil painting. Waterbased acrylic binders were first introduced as housepaints and soon artists (the first artists were mexican muralists) began to explore the potential of the new paint made with its acrylic binders, filler, pigment and water.
Regardless of this initial use of household paint in paintings, artists typically use artist quality materials from start to finish to ensure longevity. Acrylic artist paints are their own unique media. They can be used in a variety of thicknesses. For instance, they can be thinned with water and made into washes to be used similar to how watercolor paints are used. These washes are permanent and cannot be “lifted” as one might with watercolour to get additional effects.
The main difference of acrylics and oil paints is the inherent drying time. Oils allow for more time to blend colors and apply even glazes over underpaintings, etc. This slow drying aspect of oil can be seen as an advantage for certain techniques, but in other regards it impedes the artist trying to work quickly. The fast evaporation of water from the acrylic paint film can be slowed with the use of retarders. Retarders are generally glycol or glycerine based additives. In the case of acrylic paints, the addition of a retarder slows the evaporation rate of the water, and allows for more water to be added and the paint kept workable, until the retarder has left the film and the paint layer is dry.
Acrylic paints can be made to be either a high gloss, matte or anywhere in between. Matting agents cand topcoats or vanishes may also be applied to alter sheen. Acrylic paint is generally non removable when it is dry. Acrylic will not form a stable paint film if it has been thinned with too much water (more than 50% is too much). However, the viscosity of acrylic can successfully be reduced by using suitable extenders that maintain the integrity the paint film.
Acrylic painters modify the appearance, hardness, flexibility, texture, and other characteristics of the paint surface using acrylic mediums. Watercolor and oil painters also use various mediums, but the range of acrylic mediums is much greater. Acrylics have the ability to bond to many different surfaces, and mediums can be used to adjust their binding characteristics. Acrylic paint can change the sheen from gloss to matte, or can add iridescence or texture to the surface. They can also be used to build thick layers of paint: gel and molding paste mediums are sometimes used to create paintings with relief features that are literally sculptural.
Acrylic paintings should ideally be recognized as being different from oil paintings. Acrylic paintings are a distinct art medium with its own advantages as well as limitations, rather than as a stand-in for other mediums. There are techniques which are available only to acrylic painters, as well as restrictions unique to acrylic painting. Therefore, judging an acrylic painting as though it were an oil painting (or a watercolor) is not always appropriate. While canvas needs to be properly primed and gessoed before painting with oil, acrylic can be safely applied to raw canvas. The fast drying time forces the acrylic painter to work at a much faster pace than an oil painter, or abandon blending all together. While acrylic retarders can slow drying time to several hours, it still doesn't come close to the 3 days or more of open time found in oil paint, and the addition of too much acrylic retarder can prevent the paint from ever drying properly.
Although the permanency of acrylics is sometimes debated by conservators, they appear more stable than oil paints. Whereas oil paints normally turn yellow as they age/dry(oxidize), acrylic paints, at least in the 50 years since invention, do not yellow, crack, or change.