This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
Blue paving bricks may be produced with almost any kind of clay that will stand a fair amount of heat, by adopting the same methods as in the former case of blood-red bricks, that is, the clay may be stained throughout, or an outside coating may be applied.
Ground ironstone. ... 20 parts
Chromate of iron..... 5 parts
Manganese......... 6 parts
Oxide of nickel...... 1 part
Use 1 part clay and 1 part stain for coating, and 50 or 60 parts clay and 1 part stain for staining through. Fire blue paviors very hard.
Buff fire clay........ 16 parts
China clay......... 6 parts
Yellow ocher........ 3 parts
Ball clay............ 10 parts
Flint.............. 4 parts
Add water to the materials after mixing well, pass through the fine lawn, and dip the goods when soft in the liquid.
Ground flint glass..... 4 parts
Ground white lead.... 4 parts
Ground oxide of zinc. 1/2 part
This glaze is suitable for bricks or tiles made of very good red clay, the natural color of the clay showing through the glaze. The goods must first be fired sufficiently hard to make them durable, afterwards glazed, and fired again. The glaze being comparatively soft will fuse at about half the heat required for the first burning. The glaze may be stained, if desired, with any of the colors given in glazed-brick recipes, in the following proportions: Stain, 1 part; glaze, 1 part.