In painting

Painting

Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...

, a retarder is a substance, usually added to water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, used to slow the drying time of acrylic paints, giving more time for blending or layering

Layering

Layering is a means of plant propagation in which a portion of an aerial stem grows roots while still attached to the parent plant and then detaches as an independent plant. Layering has evolved as a common means of vegetative propagation of numerous species in natural environments...

 highlights.

Use in fine art

Retarders are used to counter the fast drying properties of acrylic paints making possible the usage of wet on wet or other techniques which would otherwise require oil paints. Even if they will never give acrylic the working time oil paints permits, depending how much it is adding to paint, they can give anywhere from half an hour to a full day's working time.

Content

They generally contain glycol (such as propylene glycol

Propylene glycol

Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic compound with formula C3H8O2 or HO-CH2-CHOH-CH3...

) or glycerin-based additives.

Home-Made

For home-made acrylic retarder, water glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

down about 5:1 (water: glycerol) and apply to paint. Non-toxic car anti-freeze, which contains propylene glycol can also be used.