Glassblowing Techniques: Time to Blow
The batch of glass is mixed and ready to go. Glancing around the glassblower's workshop (called a hot shop), we see a number of tools and equipment that'll soon be in use.
First is the initial furnace, inside of which is a pot (sometimes called a crucible). In a process called charging, the furnace is filled with large amounts of batch that melt at temperatures higher than 2,000 degrees Fahrenheit (about 1,100 degrees Celsius).
While glassblowing can be done individually, it's so challenging that it's often done by a team. When things start to really get underway, the lead glassblower, called the gaffer, reaches for his blowpipe, which is usually made of iron or steel and measures about 4 feet (1.2 meters) long. The blowpipe is dipped into the furnace and comes out with a gob of molten glass on the end. After the glass is secured, the other end of the pipe is cooled off in a barrel of water.
Once the gaffer is ready, he'll blow through the tube and start to create a growing bubble in the glass. Whenever not blowing, the end of the tube is capped so the hot air remains in the glass and helps it retain its shape. More layers of glass can be gathered and added with a gathering iron, or by dipping the glass attached to the blowpipe back in the batch.
Glassblowers often make use of a large, flat surface called a marver to roll and shape the glass. Several tools are also used while working the glass. A block is a wetted wooden shaping tool, as is a bladed tool called a jack. Heat shields and paddles are often employed to shield the blower from extreme heat. The paddles can also double as a tools to smooth out hot glass. Tweezers are another tool useful for grabbing and manipulating pieces of hot glass.
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During the blowing process, the parison -- or partially blown glass -- is turned around and around and bits of glass are often added with the use of a smaller metal rod called a punty, as are various colorants. Additional glass can be joined in a number of ways. For example, it can be laminated on with heat or adhesive, threads and wraps can be laid in decorative patterns as the glass is turned, or shards can be melted in. While all this pulling and shaping is going on, a metal rod called a pontil is attached to the base of the blown glass to hold it while the mouth end is being shaped. The pontil mark is usually ground or polished away later.
While the glass is being blown, but before it's completely finished, it often cools to the point where it's unworkable, which is where the glory hole comes in. The glory hole is the second furnace in the modern three-furnace setup. It's commonly a round, insulated cylinder and the partially formed glass can be held suspended from the end of the rotating blowpipe, which rests on metal stands called yokes, until it's hot enough to continue.
Although a piece of glass may appear done when the last gob has been melted in, there's still a crucial step that needs to take place. Find out about this final bit of the process on the next page.