Origin and Composition - Description of a Few Varieties in ordinary use - How to clean Water Bottles, Furred Decanters, Tumblers, Mirrors, Globes - Origin of Windows - How to clean Picture Glasses - Opaque Windows.
GLASS is a composition made by blending melted sand and certain alkalies, principally potash and soda. These ingredients are melted in a furnace for 50 or 60 hours, and then formed into the desired shape by moulding or blowing. After which they are toughened or annealed by cooling very gradually, to prevent the glass from breaking, 24 hours being necessary for small articles, and 36 hours for larger ones.
It was discovered accidentally by some merchants in Syria who were shipwrecked, and who, finding a sufficiency of the plant Kali on the shore, used it to make a fire; the ashes of the plant, mixing with the sand, produced glass. This first glass was not transparent : the art of making it clear not being discovered until some centuries later. Ancient specimens have been found in old Egyptian tombs, some of which are now to be seen in the British Museum. Nero is said to have given ,£50,000 for two small cups of transparent glass. Many curious shapes are formed by blowing; the glass is then baked in order to retain its shape.
Pouring molten glass into steel moulds produces dishes, plates, jugs, etc., at a wonderfully low cost. The glass is taken from the mould before it is quite cold; it can be left as a plate, or be bent at the sides to form a deeper dish This is the cheapest form; butter dishes, sugar basins, dishes for stewed fruit and sweets can be purchased for a few pence, and if kept clean and bright, the glass looks very well, especially in the form of a dish, as the smooth upper surface veils the roughness of the moulding.
In order to obtain the best effect the glass used must be of a highly refractive power: this in itself is costly.
The superiority of English glass is said to be owing to the introduction in its manufacture of red lead; that made in Germany usually possesses a bluish shade.
Either moulded or cut glass must be well brushed to prevent any dirt from lodging in the indentations.
ENGRAVED glass. This process is only attempted on good material, as it is a somewhat lengthy and difficult process. A wax stencilling is placed on the glass, and the spaces forming the pattern are engraved by holding the glass over a wheel sending out a blast of sand, which thus eats into the unprotected parts.
ICED OR FROSTED glass is also expensive, and requires to be kept scrupulously clean to obtain its full beauty.
OBSCURED OR GROUND glass is obtained by holding plain clear glass over a rotatory sand wheel. It is apt to become discoloured.
ETCHED glass. This is a costly article; the glass being protected with wax while the pattern is etched with a fine needle. A cheap German imitation is easily obtained; the pattern is simply printed on with strong acid, which burns, or eats out the design.