This color contains the following pigments:
iron oxides with manganese silicates or dioxide
Fe2O3,MnO2 or Fe2O3 + MnO2 + nH2O + Si + Al2O3
Burnt Umber is a more intense reddish brown pigment that results from heating the clay pigment Raw Umber. It has medium to excellent tinting strength and high opacity, and it is quick drying in oil form. Burnt Umber is somewhat more transparent than Raw Umber. It has excellent color properties and can create a variety of subtle, clear tints when mixed with white. It can tend towards chalkiness in dark mixes in oil form, but overall it mixes well with other colors. To create a black color in oil form, mix Burnt Umber with Phthalo Blue or Ultramarine. To achieve a similar color in watercolor form, mix it with Ultramarine or Payne's Gray.
Burnt Umber has good permanence.
Burnt Umber itself is considered non-toxic. If contaminated by manganese compounds, it may be highly toxic if inhaled and moderately toxic if ingested.
This pigment gets its name from the Latin word umbra, meaning shadow or shade. Its full name is listed as terra di ombra, meaning earth of shadow/shade, due to its original extraction from the area of Umbria, Italy. It has been used as a pigment since prehistoric times. Currently, the finest umber comes from Cyprus.
Cr2O3 • 2 H2O or Cr2(OH3)
Viridian is the standard green and is stable, powerful, and cold with an emerald green undertone. It has a transparent hue, good tinting strength, a dark masstone that can be almost black at full strength, and a slow drying time in oil form. Viridian is commonly replaced by the darker, more saturated, and staining Phthalo Greens, but its properties make it a necessary part of the palette of an experienced landscape painter.
Viridian has excellent permanence, except in high-temperature work, and is highly valued as a glazing color.
Viridian is slightly toxic.
Viridian’s name comes from the Latin viridis, meaning green. The process for manufacturing Viridian, or Transparent Oxide of Chromium, was patented by Guignet in Paris in 1859. However, it had actually been discovered by Pannetier and Binet in 1838. Viridian replaced Verdigris, which was reactive and unstable, and Emerald Green, which was a poisonous copper aceto-arsenite used as a rat poison in the sewers of Paris.