Glass blowing is a centuries-old technique of forming a glass item by inflating a small amount of molten glass on the end of a hollow iron tube, which is also known as a blowpipe. The technique can be traced back to approximately 50 BCE in Roman Syria. Although the methods haven’t changed much over time, the technology used has come a long way.
There are two basic methods of blowing glass: offhand glass blowing and lampworking. Both involve hot, molten glass and a stainless steel or iron rod called a punty. They differ in the process by which the glass is heated and manipulated.
The basic recipe for glass has remained very much the same since it was first developed: glass is made with sand, ashes, lime, and potash, among other possible ingredients. Before glass blowing was developed, people used to wrap hot glass around molds and cores to make vessels. These were not seamless and were susceptible to leaks. Once blowing became the favored method, it spread throughout Europe, Asia and Africa. Glass became more efficient to make, and therefore more available to the common household.
The early 13th century marked the rise of the Venetian glass makers, who perfected the technique of glass blowing. In 1962, the “studio glass movement” ushered in a new era of publicly-accessible workshops and studios. Today, this art is noted as one of the fastest growing hobbies.
With offhand glass blowing, three furnaces are required. The first, called the furnace, is used to hold the hot, molten glass that is the raw material of a glassblower. The next furnace is known as the glory hole, where the piece is heated and reheated during the process of shaping and manipulating the material. The annealer or lehr is the third and final furnace, where the glass slowly cools over several days in order to reduce thermal stress.
There are many tools that glassblowers use in their craft. The blowpipe is dipped into the molten glass to collect a glob of it, which is then rolled on the marver, a hard, flat surface. After this step, an air bubble is blown into the glass through the blowpipe. Blocks are also used to shape and mold the glass. At the bench, which is the glassblower’s workstation, there are several hand tools used to further shape the material. Large bladed tweezers called jacks can be used to pull on the glass or to make more detailed adjustments, and shears are used to cut it.
Old fashioned lampworking used a flame created by an alcohol lamp and breath or bellows. The use of a lamp gave the technique its name. This method was and still is used to create beads, miniature glass items, figurines and sculptures, as well as laboratory glass such as test tubes. Now, lampworkers use an oxygen flame created by natural gas or propane torches. Molten glass is collected on the punty, then manipulated while turning the rod and constantly shaped by various hand tools. At one time, this technique was used primarily for scientific applications, but it has developed into an art form in its own right.