The color exhibited by a pigment when it is spread very thinly. Sometimes this is very different to the mass tone which is the appearance of the color when thick. Aureolin as an example is a brownish leathery looking color in mass tone, yet its under tone is a bright golden yellow of great beauty. The best grades of Burnt Sienna have a red brown mass tone and an orange under tone, and there are some reds that are quite yellowish in undertone. This property can be exploited by the artist for beautiful effects. It is something to be considered when glazing also.