refractory clay

The sides of the crucibles are covered with a thin layer of refractory clay, and their bottoms have a spherical concavity to hold the bloom.

From Scientific American Supplement, No. 430, March 29, 1884 by Various

The reliefs, so finely modelled by Flaxman, were fired, and from them moulds of a very refractory clay were made, called pitcher moulds.

From Pottery, for Artists Craftsmen & Teachers by George J. Cox

Generators.—The generator consists of a retort made of refractory clay, vertically mounted, and cylindrical or conical in form.

From Gas-Engines and Producer-Gas Plants A Practice Treatise Setting Forth the Principles of Gas-Engines and Producer Design, the Selection and Installation of an Engine, Conditions of Perfect Operation, Producer-Gas Engines and Their Possibilities, the Care of Gas-Engines and Producer-Gas Plants, with a Chapter on Volatile Hydrocarbon and Oil Engines by R. E. Mathot

This reflector terminates above in a dome, in whose center is placed a refractory clay box.

From Scientific American Supplement, No. 417, December 29, 1883 by Various

If a soft clay that contracts considerably is inlaid in a refractory clay, cracks will appear round the edges of the inlay.

From Pottery, for Artists Craftsmen & Teachers by George J. Cox