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How Lead Crystal is Made
By Bonnie Spring
Composition
Lead crystal glass is made from a mixture of sand, potash and lead oxide. The type of lead crystal glass is determined by a British specification (BS 3828: 1964) for each type. Lead crystal glass contains a minimum lead oxide content of 24% and is produced primarily for its beauty of appearance. Full lead crystal glass contains higher amounts of lead oxide usually not less than 30%. This higher content of lead oxide enhances the beauty of the item but it is more costly to manufacture.
The Glass Workshop
The workshop where the lead crystal glass making is done is an interesting scene. Workers are stationed in groups around the furnace where the glass is melted. Each group is known as a "chair" and consists of 4 or 5 persons: The "workman", who is the principal, two who are known as "foot maker" and "servitor" – and one or two boys who are employed in what we would call "gofer" positions. A certain part of the work is assigned to each member of the group, according to the design of the item on which the "chair" is making.
Any lead crystal figurine or other piece begins as a ball of molten glass. This ball is drawn from the pot on the end of a blow-iron, which is a steel tube about 4 ft. long. It is constantly rotated in order to distribute the glass evenly. The molten glass is rolled on a polished iron table to smooth the surface. The glassworker now blows through the tube and the hot glass forms into a hollow sphere. By turning, tilting and swinging the molten glass on the tube the shape begins to develop. The glass is further created as the iron is rolled up and down on the arms of the glassmaker's chair. Few tools are used in this process - a steel pincers, calipers, shears, wooden measuring sticks and clappers. Once a stem and foot are added to the piece being made it is transferred for further working to steel rod called a pontil, the end of which it is attached by a blob of hot glass. The glass is re-melting before excessive glass is sheared away from the item being made and any final touches are given. The still glowing article is cracked off the rod, dropped into a carrying case and transported to a "lehr" or annealing oven.
Annealing
The annealing oven is a long chamber through which the glass is slowly carried, passing little by little from a high temperature to the ambient temperature of the workshop. This is necessary because the glass could cool too rapidly and shatter the item being created. When removed from the lehr, each article undergoes an examination for any defects. An instrument utilizing polarized light is used to reveal any imperfect annealing.
Cutting
Cutting is one of the more critical processes and calls for a very high degree of skill. Cutting is done by holding the lead crystal figurine against the edge of a revolving cutting wheel. The glass is carefully guided to produce some of the lovely and complex patterns that are possible. The number of patterns is infinite and in combination creates some beautiful effects. The pattern which has been designated on the glass "blank" by specially trained workers, is first roughly cut by the carborundum wheel. The glass is now ready for polishing.
Polishing
Polishing is done by placing the glass into a vat containing a mixture of hydrofluoric and sulphuric acid for about a minute. It is then thoroughly rinsed and the glass transforms into sparkling pieces of crystal.
This is the process that virtually any piece of lead crystal glass goes through before it becomes a beautiful piece of art. Throughout the years little in the process has changed.
About the Author
Bonnie Spring is writer and administrator for http://www.Kbkgifts.com, where you can find beautiful crystal.
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