The Manufacturer and Builder 8, 1877
Brick becomes black through the process of baking when the brick clay has been mixed with either the protoxid of iron, the oxid of cobalt, or the peroxid of manganese; 1 part of the iron or manganese to 10 of clay is sufficient. Sometimes two or three of these ingredients are used together. To make black mortar, mix the lime with fine anthracite coal-dust instead of sand.
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