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Acrylic paint is fast-drying paint containing pigment suspension in acrylic polymer emulsion. Acrylic paints are water soluble, 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.
As early as 1934 the first usable acrylic resin dispersion was developed by German chemical company BASF, which was patented by Rohm and Haas. The synthetic paint was first used in 1940s, combining some of the properties of oil and watercolor. Between 1946 and 1949, Leonard Bocour and Sam Golden invented a solution acrylic paint under the brand Magna paint. These were mineral spirit-based paints. Acrylics were made commercially available in the 1950s. A waterborne acrylic paint called "Aquatec" would soon follow. Otto Rohm invented acrylic resin, which quickly transformed into acrylic paint. In 1953, the year that Rohm and Haas developed the first acrylic emulsions, Jose L. Gutierrez produced Politec Acrylic Artists' Colors in Mexico, and Permanent Pigments Co. of Cincinnati, Ohio, produced Liquitex colors. These two product lines were the very first acrylic emulsion artists' paints. Water-based acrylic paints were subsequently sold as latex house paints, as latex is the technical term for a suspension of polymer microparticles in water. 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 best exterior water-based paints are 100% acrylic, due to elasticity and other factors, but vinyl costs half of what 100 percent acrylic resins cost, and PVA (polyvinyl acetate) is even cheaper, so paint companies make many combinations of them to match the market.
Soon after the water-based acrylic binders were introduced as house paints, artists and companies alike began to explore the potential of the new binders. Water-soluble artists' acrylic paints became commercially available in the 1950s, offered by Liquitex, with high-viscosity paints similar to those made today becoming available in the early 1960s. In 1963, Rowney (now part of Daler-Rowney since 1983) was the first manufacturer to introduce an artist’s acrylic color in Europe, under the brand name Cryla.
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 with gloss or matte finishes are common, although a satin (semi-matte) sheen is most common; some brands exhibit a range of finish (e.g., heavy-body paints from Golden, Liquitex, Winsor & Newton and Daler-Rowney). Politec acrylics are fully matte. As with oils, pigment amounts and particle size or shape can naturally affect the paint sheen. Matting agents can also be added during manufacture to dull the finish. The artist can mix media with their paints and use topcoats or varnishes to alter or unify sheen if desired.
When dry, acrylic paint is generally non-removable from a solid surface. 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 may result in removal of all of the paint layers, acrylic gesso, etc. Oils and warm, soapy water can remove acrylic paint from skin.
Only a proper, artist-grade acrylic gesso should be used to prime canvas in preparation for painting with acrylic (however, acrylic paint can be applied to raw canvas if so desired without any negative effect or chemical reaction as would be the case with oils). It is important to avoid adding non-stable or non-archival elements to the gesso upon application. 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 slow drying and extend workability time and flow releases to increase color-blending ability.
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Prior to the 19th century, artists mixed their own paints, which allowed them to achieve the desired color and thickness and to control the use of fillers, if any. While suitable media and raw pigments are available for the individual production of acrylic paint, hand mixing may not be practical due to the fast drying time and other technical issues.
Acrylic painters can modify the appearance, hardness, flexibility, texture, and other characteristics of the paint surface by using acrylic media or simply by adding water. 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. Acrylics can be used on paper, canvas and a range of other materials. However, their use on engineered woods such as medium-density fiberboard can be problematic because of the porous nature of those surfaces. In these cases it is recommended that the surface first be sealed with an appropriate sealer. Acrylics can be applied in thin layers or washes to create effects that resemble watercolors and other water-based media. 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 also used in hobbies such as train, car, house, and human models. People who make such models use acrylic paint to build facial features on dolls or raised details on other types of models. Acrylic paint is easily removed from paint brushes and skin with water, unlike oil paints that require the use of a hydrocarbon.
Acrylic paints are the most common paints used in grattage. Grattage is a surrealist technique that became popular with the release of acrylic paint. Acrylics are used for this purpose because they easily scrape or peel from a surface.
Commercial acrylic paints come in three grades:
The vehicle and binder of oil paints is linseed oil or another drying oil, whereas water serves as the vehicle for an emulsion (suspension) of acrylic polymer that is the binder in acrylic paint. Thus, oil paint is said to be "oil-based", whereas acrylic paint is "water-based" (or sometimes "water-borne").
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. 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.
Oil paints may 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-miscible oil paints have been developed for artists' use. Oil paint films can become increasingly 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 has a higher pigment load than acrylic paint. As linseed oil has a smaller molecule than acrylic, oil paint is able to absorb substantially more pigment. Oil provides a different (less clear) refractive index than acrylic dispersions, imparting a unique "look and feel" to the resultant paint film. Not all pigments in oil are available in acrylic. Acrylic paints, unlike oil, may also be fluorescent.
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. It usually takes between fifteen to twenty minutes for one to two layer of acrylic paint to dry. Although canvas needs to be properly sized and primed before painting with oil (otherwise it will eventually rot the canvas), 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 as in oil painting. Even though 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.
Meanwhile, acrylic paint is very elastic, which prevents cracking from occurring. Acrylic paint's binder is acrylic polymer emulsion; as this binder dries the paint remains flexible.
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. This versatility is also illustrated in the wide variety of additional artistic uses that acrylics afford the artist. Specialist acrylics have been manufactured and used for lino block printing (acrylic block printing ink produced by Derivan since the early 1980s), face painting, airbrushing, watercolor techniques, and fabric screen printing.