Sunday, March 30, 2008

How to make a glass

In this century, the existence of glass is undeniable. Glass is everywhere in many forms as a bottle, window, mirror, etc. Nevertheless, do you know how to make a glass? Traditionally It’s quite simple and generally it’s merely consisted of three main steps : chemistry reaction, molding, and finishing. Firstly, primary materials of glass, such as sand, flint, spar, or some other siliceous substances (white sand) with one or other of the fixed alkalies (soda), and in some cases with a metallic oxide, mixed and kept in a storage furnace. Litharge (kind of lead preparation) as metallic oxide usually used but iron is preferred in bottle-glass. This materials must be reduced to powder before heating (For this purpose we can use mortars or by horse mill) and it sent to the calcining furnace for stirring and and then glass furnace with temperature controller for heating (5 or 6 hours) in 17000 C. As the result is called frit as the best form to make a glass. To purify this coarse matter we can use flux such as lead, borax (for the best looking-glasses), arsenic, nitre, or any alkaline matter. Flux will bind the waste or unwanted substances.

Second step is molding. After cooling down, the compound is being removed through the pipes. This pipes are separated into two flows, one directed to a temporary storage to make the plate glass and the other one is directed to a removable mold to make the bottle glass. In the first flow, there is a rolling pin system, which is compound move below it, with flat mold for pressing the frit (glass compound) and make it into thin and flat form. The second flow is different. To make a bottle glass, the removable mold is filled by glass compound and then it blown to make bottle shape that we want. It’s blown until the compound is robust and hard.

Finally, the flat glass and the bottle glass are manipulated with additional process such as coloring, carving, decorating, etc. Those processes are depend to the function of the glass and of course to the costumer’s demand. Now they are finished and ready to used.

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