How glass is made
The most beautiful sheet of glass starts with the most common materials: sand, soda ash, limestone and other components.
The process begins when the correct mixture of ingredients becomes molten at 1350 degrees Celsius in a furnace. The molten glass is then poured into sheets using one of several methods. Sheets need to be transferred to anneal in a kiln/lehr. The cooling of glass must be controlled and slow to avoid stress in the glass.
Hand cast glass is ladled onto a flat surface.
It is then rolled to a consistent thickness.
Mottled glass, as an example, is named for the crystal growth that forms circular patterns of colour. It has a dimensional quality due in part to the colour mix, the variations in colour density and the textural surface created by the mottling.
Machine rolled glass is more consistent in thickness and size. Typically, the molten glass is fed into a pair of counter-rolling metal rollers onto a moving line towards the lehr. Special textures and surface patterns can be made on the glass with specifically designed rollers. A good example is Cathedral style textured glass.
It comes in a variety of patterns such as Ripple, Hammered, Granite, Flemish amongst others.
There are many types of cathedral glass:
Seedy glass has a slight texture caused by air bubbles trapped in the single-coloured sheet during the manufacturing process.
Wispy, Streaky and Cloudy are names that describe a mostly transparent, cathedral style glass that also mellow opalescent streaks of colour throughout.
Opalescent glass is non transparent and can come in single colours or a swirl of two or more colours.
Mouth blown antique” glass is made in the traditional manner. A “gather” of molten glass is taken from the furnace at the end of a punti rod or blow pipe. The gather is enlarged to a cylindrical shape. The ends are cut off and the cylinder is cut lengthwise before reheating to flatten into a sheet. While giving the glass its first shape, the glass blower imparts the characteristic crystalline striations that identify glass as mouth blown. Rich colour is also typical of antique and flashed glass.
Antique glass is transparent yet distorts images because of its crystalline qualities.
Flashed glass is a mouth blown sheet of glass that has a thin layer of another colour glass “flashed” on one side. The combination gives the glass a dense, flat colour.