In the section “Prof. Theo de Beer about ….” we share with you articles from the unpublished book of Professor Theo de Beer “Everything about art materials”. Prof. Theo de Beer managed the Old Holland company from 1982 till 2000 and made a huge contribution to its development.
We have known raw sienna since antiquity. This natural iron oxide used to be excavated in central Italy, near Sienna (in the province of Tuscany), that is why it is also sometimes called Italian earth.
These days, just as with ochre, the pigment is often found in the German Harz mountains and on the islands of Corsica and Sardinia. The mined earth is washed, purified, dried and sieved. Natural iron oxide (earth paint) is P.BR.7.
Raw sienna has no tinting strength but it is lightfast. It needs a great deal of binder, which gives the paint a transparent characteristic. This makes it easy to use for the glazing technique. The layer of oil paint will start to wrinkle if you suddenly apply it in thick layers.
Raw sienna has a deeper and warmer colour than gold ochre.
Burnt sienna is made by heating raw sienna, giving the pigment a darker colour. Burnt natural iron oxide (earth paint) is P.BR.7.
Burnt sienna has high colour strength, is lightfast and has slight opacity, because the colour is dark. The pigment has a glazing effect and produces a strong, hard layer of oil paint. Burnt sienna has a beautiful undertone, which radiates a warm glow, something other pigments cannot equal. You can strengthen this property even more by adding a little clear red paint.
When mixed with ultramarine, you can mix a neutral colour. When used as a watercolour, the pigment particles sometimes remain visible on the paper. This depends on the particle size, which depends on where it was found.