Glass Blowing Secrets
Glass blowing secrets: glass is all around us, but do you know how it is made? Find out all about the fascinating glass trade.
Glass making is one of mankind’s oldest trades. Although man has utilised glass for more than 3,500 years, however, it is only in the last 100 years that he has been able to make use of its amazing versatility. In fact, it was as late as 1903 that glass bottle automation was invented and 1916 before a machine for flat-drawing window glass was devised.
The basic ingredients of glass have, though, remained the same for thousands of years. They are Silica sand, lime and soda. These ingredients are mixed by the ton and fed into a gigantic tank furnace that can hold more than a thousand tons of molten glass. The furnace must be heated to 2,800 degrees Fahrenheit.
Once started this operation continues day and night, with a batch continuously being fed into one end and workable glass being drawn from the other. The red-hot liquid is then ready to be drawn, pressed or blown into shape.
Ordinary window glass is drawn from the drawing kiln, a small extension of the furnace. To begin production an iron grill bait is lowered into the melt and slowly raised. The molten glass is fluid enough to flow, yet viscous enough to adhere to the bait so that it raises in a continuous sheet. The bait is knocked off as electrically driven rollers carry the hardened liquid some 30 feet straight up to a cutting loft where the fire-polished sheet is cut into standard lengths. The glass then moves between large grinders which makes it perfectly flat.
When bottles or jars are being made, gobs of glass fall from the furnace into blank moulds. A plunger forces the glass into the shape of the initial mould and the glass is then transferred to a finishing mould where compressed air blows it into the final form.
Yet, it is the art of glass blowing that is truly enthralling to behold. Artistic glass and fine tableware are produced through this means. Glass blowers act in groups of about six. First the ‘gatherer’ collects the correct amount of molten glass onto his blowing iron – a hollow iron pipe with a mouthpiece at one end and a knob at the other. The next worker then shapes the glass by rolling it on a ‘marver’ or machine ironed plate. By blowing through the pipe, the glass is formed into a preliminary shape. Various workers add their skills to shape the glass, rotating the blowpipe constantly to keep the soft form from sagging out of shape. Swinging the bagpipe elongates the glass, rapid spinning flattens it out. Shaping tools spread an open end or pinch in a narrow neck, flatten edges, run the gob and trim off excess glass.
The gaffer is the most senior blower who oversees the jobs and undertakes the most delicate ones himself. His skill in judging the flow of the liquid and amount of air required to produce the perfect finish is quite amazing. When he is satisfied with the piece, it is placed in the annealing oven to be gradually cooled.
The finished product is a work of superb craftsmanship and skill that will give many years of visual pleasure to its owner. Unless, of course, they drop it.