painting Painting is the practice of applying paint, pigment, color or other medium to a solid surface (called the "matrix" or "support"). The medium is commonly applied to the base with a brush, but other implements, such as knives, sponges, and ...

, a retarder is a substance, usually a glycol and usually added to

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, that is used to slow the drying time of

acrylic paints Acrylic paint is a fast-drying paint made of pigment suspended in acrylic polymer emulsion and plasticizers, silicone oils, defoamers, stabilizers, or metal soaps. Most acrylic paints are water-based, but become water-resistant when dry. Depe ...

, giving more time for blending or

layering Layering has evolved as a common means of vegetative propagation of numerous species in natural environments. Layering is also utilized by horticulturists to propagate desirable plants. Natural layering typically occurs when a branch touches ...

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 Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnis ...

. When used correctly, they can keep the paint wet from half an hour extra to a full day's working time. Applying too much retardant, however, can prevent a layer from drying correctly for as long as the retardant is present, causing future damage to the painting unless the affected layer of paint is removed or re-mixed.

Content

They generally contain glycol (such as

propylene glycol Propylene glycol (IUPAC nomenclature, IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two Alcohol (chemistry), alcoho ...

) or glycerin-based additives.

Home-Made

For home-made acrylic retarder, water

glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...

down about 5:1 (water: glycerol) and apply to paint.

References

Painting materials {{art-material-stub