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Red ochre, Fe 2 O 3 ·nH 2 O, takes its reddish colour from the mineral hematite, which is an iron oxide, reddish brown when hydrated. [7] Purple ochre is a rare variant identical to red ochre chemically but of a different hue caused by different light diffraction properties associated with a greater average particle size.
Red ochre takes its reddish colour from the mineral hematite, which is an anhydrous iron oxide, and the main ingredient of rust. It was one of the earliest pigments used by man. Hand prints made by using red ochre have been found in the Pech Merle cave in Southern France. They date to between 16,000 and 25,000 BC.
Cerium sulfide red (PR265). Iron oxide pigments. Sanguine, Caput mortuum, Indian red, Venetian red, oxide red (PR102). Red ochre (PR102): anhydrous Fe 2 O 3. Burnt sienna (PBr7): a pigment produced by heating raw sienna. Lead pigments. Minium (pigment): also known as red lead, lead tetroxide, Pb 3 O 4. Mercury pigments. Vermilion or cinnabar ...
Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrated hematite (Fe 2 O 3 · H 2 O). The principal use of ochre is for tinting with a permanent color. [9] Use of the red chalk of this iron-oxide mineral in writing, drawing, and
The anhydrous pigment has a dark purple-red or maroon color, hydrates' colors vary from dull yellow (yellow ochre) to warm red. [1]The iron oxide red is extremely stable: it is not affected by light and most chemicals (soluble in hot concentrated acids); heat only affects the hydrated variants (the water is removed, and the color darkens).
The pigment is also known as red earth, red ochre, and terra rossa. On the Color Index International, the pigment is known as PR-102. This version is from the Italian Ferrario 1919 color list. The first recorded use of burnt sienna as a color name in English was in 1853. [19]
In 2022 a team of South African and French scientists published a study of otjize's physical properties, concluding that "such a red ochre exhibits an exceptional UV filtration and a significant IR reflectivity substantiating its effectiveness as an effective UV-blocking and solar heat IR reflector in support of the low skin cancer rate within the Namibian Himba community".
[1] [2] Other earth pigments include the green earth pigments or terres vertes, blue earth pigments such as vivianite-based "blue ochre", white earth pigments such as chalk, and black earth pigments such as charcoal. [3] [4] Earth pigments are known for their fast drying time in oil painting, relative inexpensiveness, and lightfastness. Cave ...