Tests on paints made from currently available vermilions indicate that their stability is below Eibner's standards: significant darkening may occur in 5 to 10 years of normal gallery exposure. A high ratio of pigment-to-vehicle causes the light to be scattered considerably, reducing the rate of darkening. In general, the degree of darkening is greatest in those paints in which the light can penetrate deepest; vermilion in linseed oil, for example, darkens more than in water color or polymer emulsion. The traditional painting technique of overglazing with madder or cochineal provided protection from darkening by reducing the intensity of light reaching the pigment.