Raw umber

Raw umber

Description

Raw umber

A pale yellowish brown natural earth pigment that contains manganese dioxide and iron hydroxide. See umber.

Synonyms and Related Terms

Pigment Brown 7; CI 77492; umbra; terre d'ombre naturelle (Fr.); Umbra natur (Deut.); ombra omi (Gr.); terra d'ombra naturale (It.); ruwe omber (Ned.); grisaille; Sicilian brown

Risks

Toxic.

Physical and Chemical Properties

• Slightly soluble in acids giving a yellow solution.
• Turns reddish brown when heated.
• Density = 3.2 g/ml
• Refractive Index = 1.87-2.17

Additional Images

• 

  Raw umber at 500s
  transmitted light

• 

  Raw umber at 500x
  Polarized light

Resources and Citations

• R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966 Comment: density = 3.20 and ref. index = 1.87-2.17
• Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
• R.D. Harley, Artists' Pigments c. 1600-1835, Butterworth Scientific, London, 1982
• Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
• Pigments Through the Ages - http://webexhibits.org/pigments/indiv/overview/umbra.html
• Website: http://www.coloria.net/varita.htm
• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
• CHSOS: Spectra (Reflectance, XRF, Raman, FTIR) for Raw umber