Keene's cement

Both processes are inferior in economy to calcination in rotatory kilns, a process which may be regarded as the method of Plaster of Paris; Keene’s cement. the present and the immediate future.

Keene’s cement and its congeners are made in fixed kilns so constructed that only the gaseous products of combustion come into contact with the gypsum to be burnt, in order to avoid contamination with the ash of the fuel.

They include plaster of Paris, Keene’s cement and many variants of these two types.

This may be almost chemically pure, when it is generally used for Keene’s cement; or it may contain smaller or greater quantities of impurities, in which case it is suitable for the preparation of cements of the plaster of Paris class.

If a cement of the Keene’s cement class is to be prepared the temperature used is higher, e.g.