Raw sienna

Raw sienna

Description

Raw sienna at 100x (visible light left; UV light right)

A dark yellow iron oxide pigment. Raw sienna is a natural earth mixture that contains at least 50% hydrated ferric oxide (goethite) mixed with alumina, clay, and some manganese dioxide. Raw sienna is a semi-opaque, permanent pigment. It was named for the south Italian city of Siena that produced fine grades of the pigment and was originally called Italian earth.

FTIR (MFA)

Raman (MFA)

SEM

EDS

Synonyms and Related Terms

Pigment Brown 7; CI 77491; Italian earth; terre de Sienne (Fr.); terra di Siena (It.); Sienaerde (Deut.); siena natural (Esp.); siena natural (Port.)

Note: All iron oxide pigments made after 2001 are designated Pigment Brown 6 (not 7)

Physical and Chemical Properties

• Color = mid valued, moderately dull earth yellow
• Density = 3.14 g/ml
• Refractive Index = 1.87-2.17

Additional Images

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  Raw sienna at 500x
  Transmitted light

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  Raw sienna at 500x
  Polarized light

Resources and Citations

• R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
• G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 577
• Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
• Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
• Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
• Art and Architecture Thesaurus Online, https://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
• CHSOS: Spectra (Reflectance, XRF, Raman, FTIR) for Raw sienna