The term "blowpipe" can refer to several different things, but for the purpose of this wiseGEEK article, we will examine the blowpipes used in the manufacture of glass. While hand-blown glass is no longer as abundant as it once was, thanks to the development of automated machines and mold, the art of blowing glass has been retained in some communities, with artisan glass pieces sometimes fetching a very high price at the market due to their unique and hand-made nature.
In glass making, a blowpipe or blow tube is a critical tool. It consists of a very long, slender pipe with a mouthpiece on one end. To use the blowpipe, a glass maker first preheats the tip, and then dips it into a vat of molten glass to pick up a chunk of glass for working known as a gather. Then, the glass maker gently blows into the blowpipe, inflating the gather to create a hollow glass piece.
Using an assortment of tools, the glass maker can shape the glass piece on the end of the blowpipe, periodically reheating the glass if necessary to keep it flexible. Once the piece is finished, it is removed from the blowpipe. In many cases, it is attached to a pipe called a puntil, then a few drops of water at the neck and a sharp rap to the blowpipe allow it to be removed. It is then annealed to strengthen it before being removed with tongs and allowed to cool. The finished piece can vary widely in size and shape, depending on the size of the gather and how the glass maker worked it.
Blowpipes first began to be used in glass making around the first century BCE, and they made a radical difference in the art of glass making. Previous techniques for creating hollowed glass objects were cumbersome, time consuming, and not very reliable. Using a blowpipe, a glass maker can turn out a high volume of glass items very quickly, especially if he or she is experienced and skilled. The elasticity of molten glass on a blowpipe can also be turned to the advantage of the crafter; the Romans, for example, produced layered glass pieces by dipping their gather in a different color of glass partway through the blowing process, creating an opalescent layer on the outside of the glass piece.
Blowpipes are also used in jewelrymaking, with modern blowpipes sometimes containing a mixture of gases delivered by machine, although people do continue to blow by hand or with sets of bellows. Automated machines have the advantage of being generally safer, but finished pieces produced by machine lack the quirky individuality of hand-formed pieces.