All constituents of which an enamel glaze is composed must be intimately mixed together. This can only be done by reducing each to a fine powder and thoroughly stirring them up together. This part of the work is often carried out in a very superficial manner, one material showing much larger lumps than another. Under circumstances such as these it is absurd to imagine that in fusion equal distribution will take place. What really happens is that some parts of the mass are insufficiently supplied with certain properties while others nave too much. A mixture of this class can produce only unsatisfactory results in every respect, for the variations referred to will produce variations in the completeness of fusion in the viscous character of the mass, and in the color.

The mixing can be done by thoroughly stirring the various ingredients together, and a much better and cheaper system is mixing in rotating barrels or churns. These are mounted on axles which rest in bearings, one axle being long enough to carry a pulley. From the driving shaft a belt is led to the cask, which then rotates at a speed of from 40 to 60 revolutions per minute, and in about a quarter of an hour the operation is complete. The cask should not exceed the 5-gallon size, and should at no time be more than two-thirds full. Two casks of this kind give better results than one twice the size. The materials are shot into the cask in their correct proportions through a large bung hole, which is then closed over by a close-fitting lid.

Mixings

For gray or fundamental coatings:

I

Almost any kind of

glass.......... 49     per cent

Oxide of lead..... 47     per cent

Fused borax...... 4     per cent

II

Glass (any kind)..   61     percent

Red lead.........   22     per cent

Borax...........   16     per cent

Niter............     1     per cent

III

Quartz.......... 67.5 per cent

Borax........... 29.5 per cent

Soda (enameling). 3 per cent The above is specially adapted for iron pipes.

IV

Frit of silica powder............ 60 per cent

Borax........... 33 per cent

White lead....... 7 per cent

Fused and then ground with— Three-tenths weight of silica frit. Clay, three-tenths weight of silica frit. Magnesia, one-sixth weight of white lead.

V

Silica............ 65 per cent

Borax........... 14 per cent

Oxide of lead..... 4 per cent

Clay............ 15 per cent

Magnesia........ 2 per cent

No. V gives a fair average of several mixings which are in use, but it can be varied slightly to suit different conditions of work.