Digitalfire Ceramic Materials Database
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|Enter the formula and formula weight directly into the Insight MDT dialog (since it records materials as formulas).|
Enter the analysis into an Insight recipe and enter the LOI using Override Calculated LOI (in the Calc menu). It will calculate the formula.
Has been used in glazes as a substitute for red iron oxide.
There are varying ideas from country to country about what this material is. Historically it was just a naturally-occurring red iron oxide containing impurities (i.e. clay minerals) or an ultra-high iron clay. Today, Crocus Martis sold by ceramic suppliers is more likely to be a soluble synthetic impure red iron sulphate or a calcined-at-900C version of the sulphate (it is insoluble). This material is not normally highly processed and therefore can produce iron specking in glazes. Normal iron oxides can be used as a substitute (although less will be needed since this material has a significant weight loss during firing).
Sulphur is released during firing and it does not decompose fully until as high at 1200C.
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By Tony Hansen
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INSIGHT is ceramic chemistry