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Acrylic paint is fast-drying paint containing pigment suspended in an acrylic polymer emulsion. Acrylic paints can be diluted with water, but become water-resistant when dry. Depending on how much the paint is diluted (with water) or modified with acrylic gels, media, or pastes, the finished acrylic painting can resemble a watercolor or an oil painting, or have its own unique characteristics not attainable with other media.
Acrylics were first made commercially available in the 1950s. These were mineral spirit-based paints called Magna offered by Bocour Artist Colors. Water-based acrylic paints were subsequently sold as "latex" house paints, although acrylic dispersion uses no latex derived from a rubber tree. Interior "latex" house paints tend to be a combination of binder (sometimes acrylic, vinyl, pva and others), filler, pigment and water. Exterior "latex" house paints may also be a "co-polymer" blend, but the very best exterior water-based paints are 100% acrylic. Soon after the water-based acrylic binders were introduced as house paints, artists (the first of whom were Mexican muralists) and companies alike began to explore the potential of the new binders. Water soluble artist quality acrylic paints became commercially available in the early 1960s, offered by Liquitex.
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. For this reason, acrylics do not lend themselves to color lifting techniques as do gum arabic based watercolor paints.
Acrylic paints can be used in high gloss or matte finishes. As with oils, pigment amounts and particle size can alter the paint sheen. Likewise, matting agents can be added to dull the finish. Topcoats or varnishes may also be applied to alter sheen.
When dry, acrylic paint is generally non-removable. Water or mild solvents do not re-solubilize it, although isopropyl alcohol can lift some fresh paint films off. Toluene and acetone can remove paint films, but they do not lift paint stains very well and are not selective. The use of a solvent to remove paint will result in removal of all of the paint layers, acrylic gesso, etc.
Only a proper, artist-grade acrylic gesso should be used to prime canvas in preparation for painting with acrylic. It is important to avoid adding non-stable or non-archival elements to the gesso upon application. Acrylic will not form a stable paint film if it has been thinned with more than 30% water content. However, the viscosity of acrylic can successfully be reduced by using suitable extenders that maintain the integrity of the paint film. There are retarders to prolong drying and workability time and a flow release to increase color blending ability.
Painters and acrylic
Prior to the 20th century, artists mixed their own paints to increase the longevity of the artwork and achieve desired pigment load, viscosity, and to control the use of fillers, if any. While suitable media and raw pigments are available for the individual production of acrylic paint, due to the fast drying time, hand mixing may not be practical.
Acrylic painters modify the appearance, hardness, flexibility, texture, and other characteristics of the paint surface using acrylic media. Watercolor and oil painters also use various media, but the range of acrylic media is much greater. Acrylics have the ability to bond to many different surfaces, and media can be used to adjust their binding characteristics. They can also be used to build thick layers of paint: gel and molding paste media are sometimes used to create paintings with relief features that are literally sculptural.
Acrylic paints are the most commonly used in grattage.
Differences between acrylic and oil paint
The vehicle and binder of oil paints is linseed oil, whereas water serves as the vehicle for an emulsion of acrylic polymer that is the binder in acrylic paint. Thus, oil paint is said to be "oil-based", while acrylic paint is "water-based"
The main practical difference between most acrylics and oil paints is the inherent drying time. Oils allow for more time to blend colors and apply even glazes over underpaintings. 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. In 2008 Golden Artist Colors introduced a slow drying acrylic paint with working qualities similar to oils, but indistiguishable from regular acrylics when completely dry. This new acrylic paint can remain wet and workable on a palette for several hours and even days under normal conditions.
The fast evaporation of water from regular acrylic paint films can be slowed with the use of acrylic retarders. Retarders are generally glycol or glycerin-based additives. The addition of a retarder slows the evaporation rate of the water, and allows for more water to be added and the paint workable, until the retarder has left the film and the paint layer is dry.
Oil paints require the use of solvents such as mineral spirits or turpentine to thin the paint and clean up; these generally have some level of toxicity and are often found objectionable. (Relatively recently, water soluble oil paints have been developed for artist use.) Oil paint films become increasing yellow and brittle with time and lose much of their flexibility in a few decades. Additionally, the rules of "fat over lean" must be employed to ensure the paint films are durable.
Oil paint is able to absorb substantially more pigment than acrylic because linseed oil has a smaller molecule than does acrylic. Oil provides a different (less clear) refractive index than acrylic dispersions, imparting a unique "look and feel" to the resultant paint film.
Due to acrylic's more flexible nature and more consistent drying time between colors, the painter does not have to follow the "fat over lean" rule of oil painting, where more medium must be applied to each layer to avoid cracking. While canvas needs to be properly primed and gessoed before painting with oil, acrylic can be safely applied to raw canvas. The rapid drying of the paint tends to discourage the blending of color and use of wet-in-wet technique unique to oil painting. While acrylic retarders can slow drying time to several hours, it remains a relatively fast-drying medium, 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)—and require a removable protective layer of varnish—acrylic paints, at least in the 50 years since their invention, have not yellowed, cracked, or altered.
Another difference between oil and acrylic paints is the versatility offered by acrylic paints - acrylic is very useful in mixed media, allowing use of pastel (oil & chalk), charcoal, pen, etc. on top of the dried acrylic painted surface. Mixing other bodies into the acrylic is possible - sand, rice, even pasta may be incorporated in the artwork. Mixing artist or student quality acrylic paint with household acrylic emulsions is possible, allowing the use of pre-mixed tints straight from the tube or tin, so presenting the painter with a vast color range at his or her disposal.
Some popular manufacturers of artist acrylics
Subsidiaries of Col Art include Winsor & Newton (Artists Acrylic, Galeria), Royal Talens (Amsterdam all Acrylics), Liquitex, and Lefranc & Bourgeois acrylics. Daler-Rowney (Cryla and System 3 ) is another English manufacturer of acrylic paint.
In the United States, manufacturers of artist acrylic paints include Golden Artist Colors, based in New Berlin, New York, Liquitex, Nova Color Artists Acrylic Paint and Daniel Smith Artists' Materials. These offer a full range of professional paints and media. M. Graham, based in Oregon, also produces a limited range of professional-quality acrylics.
Grumbacher Academy Acrylics, also manufactured in the United States Leeds, Massachusetts, offer a 24 color collegiate grade line with matching media.
D. L. Stevenson & Son Ltd., manufacturers of professional artist quality acrylics, are located in Toronto, Canada. Stevenson Acrylics consists of a line of 64 colors as well as a variety of media. (Wikipedia)