Blown Glass & Blown Press Glass

Glassblowing is a glass forming technique which was invented by the Phoenicians at approximately 50 B.C. somewhere along the Syro-Palestinian coast. The earliest evidence of glassblowing comes from a collection of waste from a glass workshop, including fragments of glass tubes, glass rods and tiny blown bottles, which was dumped in a mikvah, a ritual bath in the Jewish Quarter of Old City of Jerusalem dated from 37 to 4 B.C.

Glass Blowing is a Glass Forming Technique that involves inflating the Molten Glass into a bubble with the help of the blow pipe or blow tube. A person who blows glass is called a Glass blower, Glass smith or Gaffer.

The transformation of raw materials into glass takes place around 1300°C. The glass emits enough heat to appear almost White Hot. The glass is then left to "fine out" and allow the bubbles to rise out of the mass and then the working temperature is reduced in the furnace to around 1100°C. At this stage, the glass appears to be a Bright Orange Color. Most glassblowing is done between 870–1040°C. The "Sodalime" glass remains somewhat plastic and workable as low as 730°C. Annealing is usually done between 430–480°C.

Glassblowing involves Three Furnaces. The first, which contains the molten glass, is simply called the Glass Furnace. The second is called the Glory Hole and is used to reheat a piece in between steps of working with it. The final furnace is called the Lehr or Annealer and is used to slowly cool the glass, over a period of a few hours to a few days, depending on the size of the pieces. This keeps the glass from cracking due to thermal stress. Historically, all three furnaces were contained in one, with a set of progressively cooler chambers for each of the three purposes. Many glassblowing studios in Mexico and South America still employ this method. Now a days generally the Main Furnace and the Glory Whole are together but the third furnace which is the Lehr is made separately. Here also the Lehr is used to anneal the small glass items but if they are big in size, generally a Cooliman Furnace is used.

The Studio Glass Movement started in 1962 when Harvey Littleton a Ceramics Professor and Dominick Labino a Chemist and Engineer held two workshops at the Toledo Museum of Art during which they started experimenting with melting glass in a small furnace and creating blown glass art. Thus Littleton and Labino are credited with being the first to make molten glass available to artists working in private studios. This approach to glassblowing blossomed into a worldwide movement, producing many flamboyant and prolific artists.

The Modern Glass Factories work in a three tier system as the Batch House, the Hot End and the Cold End. The Batch House handles the Raw Materials, the Hot End  handles the furnaces and the entire manufacturing process and the Cold End  handles the product inspection and packaging. The Batch House holds the raw materials for glass like Sand, Soda Ash, Limestone, Feldspar etc. The materials are received generally by truck or rail transport and elevated into storage silos from where using common glass batch calculation, they are weighed out as multi tonne batches.

Batch feed Dog House of a Glass Furnace. In the beginning the batch is fed into the furnace at a slow controlled rate. Most of the glass furnaces are run by Natural Gas now but Coal and Fuel Oil were used in the past. They operate at temperatures up to 1675°C. The temperature is limited only by the quality of the furnace superstructure material and by the glass composition.

     LIVE WITH STYLE

                                                                                              Other Link :  http://www.woodcraft7.com