Sienna (PBr. 6 or PBr. 7) is a natural earthy light-brown pigment with high Iron Hydroxide concentration and almost no clay. In artists’ palettes you can find several kinds of sienna: Natural, Burnt, Raw, Terra Di Sienna, and other sub-kinds. The name Sienna comes from Toscana, Italy, where this mineral was found and commonly used. Some other deposits are also found in Germany and the USA. All kinds of Sienna are non-toxic.
Natural or Raw Sienna has dark brown shade and can be successfully used for glazing. If mixed with white Raw Sienna has yellowish tone. One of key benefits of Sienna is its high light fastness and natural shade. In oil painting Sienna can turn brown with time. Also since it absorbs a lot of oil Sienna dries very slowly.
Sienna can be easily mixed with any other colours with a little exception: it doesn’t like light cadmium paints. Being burnt at 500-650° С Raw Sienna turns into Burnt Sienna, which has reddish-brown colour. Burnt Sienna has rich shade, high opacity and light fastness. It’s widely used for sanguine chalks as well.
Sienna is being used in painting for centuries. As a natural pigment, it (along with its cousins ochre and umber) was one of the first pigments to be used by humans, and is found in many cave paintings. Terra di Sienna was one of the favorite colours of ancient Roman painters and was very popular among Renaissance artists.
Since PBr. 6 and PBr. 7 are inexpensive pigments, almost all manufactures produce Sienna as a mono-pigment paint.