Acrylic paint is assumed to be as durable as oil paint because usually the same pigments are used in both types of paint. However acrylic resins are a recent discovery and time has yet to confirm this. Unlike oil paint, acrylic paint is made of a thick polymer emulsion with pigment (colour) evenly mixed throughout. There is no settling of the pigment as the paint sets. This means that cleaning acrylic paintings relies on removing any dirt from the surface of the paint or a thin layer of the paint itself. Any embedded marks cannot be removed without removing colour pigment.
Acrylic paints can be bought in sets of small tubes,
larger artist tubes or pots and are cheaper than oils paints.
Being a form of plastic, acrylic emulsion (the non pigment component of the paint) degrades with prolonged exposure to ultraviolet light so acrylic paintings should not be hung opposite windows that receive full sun. Some creosotes from smoke (eg an open fireplace or an area with heavy smokers) can etch into the emulsion causing permanent discoloration. Acrylic paint sets by water evaporating out of the emulsion. Microscopically the paint is pitted at the surface. This "tooth" as it is called in an ideal surface for mould and fungi and dirt to adhere to, so once fully dry all acrylics should be treated with a surface sealant. This also helps with preservation in the future.
There are a range of acrylic mediums to alter the paint characteristics
(eg. impasto for a 3-D effect). Dried finished paintings need to be varnished
to seal the easily stained porous paint surface and prevent etching and staining
airborne creasotes, fly spots etc.
Unfortunately acrylic polymers haven't been in use to withstand the tests of time, like oils. Technology claims that acrylic paints can last as long as oils in the right conditions but time will tell.
From the artist's point of view, acrylics are cheaper to buy and dry quickly therefore reducing the time taken to finish a painting. They also require a different painting technique. Because the paints dry faster colours are more frequently mixed to the desired hue on the artist's palette, rather than on the canvas. Many painters will paint in either Acrylics or Oils but seldom paint in both types of medium on a regular basis. After painting in Acrylics your technique and construction of a painting alters. You tend to plan a painting in finished layers, adding detail onto dry coats of paint unlike oils which are worked often wet. There are emulsions that can slow down the drying time of acrylic paint to give it properties more like oils.
Acrylics can yield more profit, if selling to the decorator market. The paintings can be completed faster because of the reduced drying times. The materials cost less and if you are selling in the decorator market, you will get the same price for an acrylic painting as an oil painting.
However in the gallery and collectors market, an oil painting will usually fetch more. The acrylic paintings are more difficult to restore and unlike oils do not have a removable glaze surface for cleaning (see oil painting for more details).
From a restoration viewpoint, they are difficult to restore if damaged because the paint has to be colour matched and acrylics change hue slightly when drying, a allowance has to be made for this in the colour matching process.