Clay, compositions plastic refractory

Bottger Ware. A dark red stoneware. Bolting Clay. Prepared plastic refractory material for use in the stopping of the tap-holes in cupolas. A typical composition would be 50-75% fireclay, up to 50% black sand, 10% coal dust and up to 5% sawdust. 

Composite Refractory. A refractory brick, different parts of which have different compositions and/or textures, e.g. an insulating refractory having a dense working face, or a metal-cased basic refractory having internal partitions filled alternately with magnesite and chrome-magnesite. Composition Brick. Scottish term for a common building brick made by the stiff-plastic process from clay and colliery waste characteristically, it has a black core. 

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