Umb

Umb, a brown earthy mineral used as a pigment. It is found in Italy, Cyprus, England, and other countries. Like Ochre (q.v.), umb contains a large proportion of sesquioxide of iron, but it differs from ochre in containing, to the extent of about one-fifth of its weight, one of the higher oxides of manganese. The mineral is prepared for use as a pigment by grinding it to a powder, washing it with water, and then drying it at 212° F. When so treated it is known as raw umb, and is of a pleasing but rather pale grayish-brown hue. Burnt umb is prepared from raw umb by calcination, and is of a darker, richer, and more transparent brown colour. Both kinds are permanent either as water-colours or oil-colours, and burnt umb especially is much used by artists as well as by house-painters. Umb was one of the colours employed by the old masters.