Acrylic retarder
In painting, a retarder is a substance, usually added to water, used to slow the drying time of acrylic paints, giving more time for blending or layering 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) or glycerin-based additives.
Home-Made
For home-made acrylic retarder, water glycerol down about 5:1 (water: glycerol) and apply to paint.[1] Non-toxic car anti-freeze, which contains propylene glycol can also be used.