[722] Slate Pencils and School Crayons.

Manufacturer and builder 8, 1873

Mix a small but sufficient quantity of pipe-clay and gine-water with the slate-dust so as to make a thick paste. A small quantity of this rolled between two boards gives a slate-pencil; when too hard, use less gine-water. The school crayons are made of Paris white (which is very fine chalk) mixed with water to a paste, then a little plaster of Paris is thoroughly mixed with a small quantity of this paste, and it is pressed in proper forms. When too hard, you have too much plaster of Paris; when too soft, so that it crumbles too easy, you have not enough of the plaster. The proper quantity is easily found by trial, and depends on the hardness desired, and on the quality of the plaster used.

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