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Silica

ssss1.See “British Glass Sands” (Boswell), “British Glassmaking Sands” (Peddle); papers read at the third meeting, Society of Glass Technology, Sheffield, for further information.

The alkalies, potash or soda, or a mixture of both, are commonly used in making glass in the form either of carbonates, sulphates, or nitrates. The soda and potash silicates form very fusible glasses, but they are not permanent, being soluble in water; therefore they cannot be used alone. In making glassware for domestic use, other bases, such as lead oxide, barium, or lime, have to be added to form more insoluble combinations with the silica or sand.

Carbonate of PotashPearlash

Potash and soda each have an influence upon the colour of the resulting glasses in which they are respectively used. The potash silicate gives better and clearer glasses than the soda silicate.

Carbonate of SodaSoda Ash

Sulphate of SodaSalt Cake

Potash NitrateSaltpetre

Sodium NitrateChili Nitre

Boric Acid

BoraxBorate of Soda

TincalBorate of Lime