(Sources: Manganese Dioxide)

-Manganese monoxide exists only above 1080C where the dioxide form disassociates to release its oxygen.

-Manganese is a colorant using in bodies and glazes, producing blacks, browns, and purples.

-Manganese is a constituent in many igneous rocks, and thus occurs in many clays weathered from these parent rocks. In most cases it is a very minor oxide, but does occur in much greater amounts in some slip and highly stained materials. It is thus a color contributor in many traditional and historic slip glazes.

-Smaller amounts are easily dissolved in most glaze melts; however, around the 5% threshold, the manganese will precipitate and crystallize. In large amounts in a glaze (i.e. 20%), metallic surfaces are likely.

-Above 1080C, half of the oxygen disassociates to produce MnO, a flux which immediately reacts with silica to produce violet colors in the absence of alumina, browns in its presence. Manganese browns have a different, often more pleasant character than iron browns.

-High temperature glazes well above 1080C can use large amounts of manganese to produce very metallic bronze-like surfaces. Manganese dioxide by itself can be used and will fuse well, even running down the ware.

-Manganous oxide is unaffected by reduction, but is normally considered, at its best, in oxidation slips and glazes above 1200C.

-Manganese fuses and dissolves very well above 1200C in oxidation. Like iron, it will dissolve to a greater extent in a hotter melt. This means that if more than about 4% MnO is used, the oversupply will precipitate on cooling leaving a network of crystals in a manner similar to iron in high fire reduction. Speed of cooling, glaze fluidity, and amount of manganese will all affect the results.

Properties

• Glaze Color - Brown

  Very pleasing tan-brown reduction fired glazes can be achieved with 5% manganese dioxide in reduction.

• Glaze Color - Brown

  In glazes below 1080C, it can give coffee color browns when used with tin and dull browns in lead and low alkaline glazes.

Authors

• Tony Hansen (Owner)

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