High-manganese black-burning body at cone 6. Practical and safe to use?

This type of clay is made by a number of North American manufacturers. In this case, raw or burnt umber are used as the stain (10% or more). The umber is a clay that matures at low temperatures, so it acts as a flux in the body. However, some manufacturers make the mistake of adding it to a cone 6 body and the result is shown here: bubbling of the glaze (in this case it is a transparent) and bloating and warping of the body. The umber is decomposing and potentially gassing metal fumes. However, if the umber is added to a cone 10 clay the resultant body matures at around cone 6 and these gassing problems do not occur.

Videos

Links

Hazards

Manganese in Clay Bodies
Manganese is used to stain clays (using black) and to impart fired speckling (as a decorative effect). It is dangerous?

Got a Question?

Buy me a coffee and we can talk