Another.—70 of purified pearl ashes; 120 of white sand; 10 of saltpetre; 1⁄2 of arsenious acid; 1⁄3 of manganese.
A third.—67 of sand; 23 of purified pearl ashes; 10 of sifted slaked lime; 1⁄4 of manganese; (5 to 8 of red lead).
A fourth.—120 of white sand; 50 of red lead; 40 of purified pearl ash; 20 of saltpetre; 1⁄3 of manganese.
A fifth.—120 of white sand; 40 of pearl ash purified; 35 of red lead; 13 of saltpetre; 1⁄12 of manganese.
A sixth.—30 of the finest sand; 20 of red lead; 8 of pearl ash purified; 2 of saltpetre; a little arsenious acid and manganese.
A seventh.—100 of sand; 45 of red lead; 35 of purified pearl ashes; 1⁄7 of manganese; 1⁄3 of arsenious acid.
8. Plate glass.—Very white sand 300 parts; dry purified soda 100 parts; carbonate of lime 43 parts; manganese 1; cullet 300.
Another.—Finest sand 720; purified soda 450; quicklime 80 parts; saltpetre 25 parts; cullet 425.
A little borax has also been prescribed; much of it communicates an exfoliating property to glass.