A retardant is an antoxidant fluid. It is combined with paints to prevent them from drying. When an artist desires to delay the painting's drying process, he/she will often use a retardant so work on the piece can be done over a number of days. Oil of cloves is a favored retardant; only a few drops are necessary to combine with oil paints to use as a retardant. Pine oil and oil of lavender are other useful retardants.