French ochres

Fig. 3.18 Square-wave voltammograms of PIGEs modified with (a) Spanish hematite, (b) yellow French ochre, (c) sienna raw, (d) Italian toast umber, and (e) greenish natural umber immersed in 0.10 M HCl. Potential scan initiated at +0.65 V in the negative direction potential step increment 4 mV square wave amplitude 25 mV frequency 5 Hz [139]...

Ochre, whose color is almost exclusively due to limonite, (a-FeOOH), is still mined in nominal quantities in South Africa and France. It is being increasingly supplanted by synthetic pigments, because of its low a-FeOOH content (20% Fe203 in French ochre, up to 55% in South African ochre and ca. 87% Fe203 in synthetic a-FeOOH) and the poorer consistency of its coloristic properties. 

Important sources of yellow ochre as an artists pigment are in France. Heaton (1928) describes in some detail the French yellow ochres (also listed by Tingry, 1804, as natural yellow ochre ). French ochre was bright yellow and derived from the Perigord, Yonne Valley and the Vaucluse. It was graded according to quality and classified as follows ... 

The recognition of hematite on works of art is common however, in many cases, the hematite is identified as a component of an ochre, umber or sienna (qq.v.). Hameau et al. (2001) hst hematite (as distinct from ochre) as a pigment from post-glacial French PalaeoUthic sites. A neoHthic pot containing unused hematite pigment has been found in Greek Macedonia (Maniatis and Tsirtsoni, 2002). Hematite adulterated with chalk, carbon and... 

Maghemite is a minor, but not unusual component of burnt ochres. It has been recorded by Pomies et al. (1999) from the French Palaeolithic site of Troubat (Pyrenees). David et al. (2001) have indicated that it is present in red and yellow ochres from Tell el Amarna, Egypt. 

Various combinations of pigments were used to produce this Field (1835) states it was composed of sepia, indigo or other blues, with madder or other lakes while the 1896 catalogue of British colourmen Winsor Newton lists neutral tint as an intimate combination of Carbon Black, Ochre, and French Ultramarine and Indigo, Cochineal lake and Carbon black for the watercolour pigment qq.v. cf. Carlyle, 2001). 

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