A note on burnt yellow earth pigments: documentary sources and scientific analysis |
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| Abstract: | AbstractThe red iron oxide pigment known as burnt yellow earth has been used as a substitute for naturally occurring red earth since earliest times. Documentary evidence indicates that this pigment was often produced by heating yellow earth for anywhere from a few minutes up to several hours at temperatures below 8000 C. When yellow earth is burnt under these conditions, its constituent goethite is transformed to red iron oxide with an anomalous diffraction pattern corresponding to a disordered haematite crystal structure. Using pigments of known origin and processing, it is shown that X-ray microdiffractometry can be used to classify very small samples of red iron oxide pigments and that, in some cases, the diffraction pattern can provide evidence to support or refute the use of burnt yellow earth. |
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