Essentially, glass blowing procure hasn’t changed much since the times of the Roman Empire. The making of glass requires a furnace, some apparatus as well are skilled staff to run the operations. It is a unique procedure and can be shocking to a new person.
• Steel tube about 1.5m (blow pipe)
• Steel table
• Silica (sand) as well as metal components to accelerate melting process like metal oxides (aluminum, boron oxide, magnesia, and lead oxide depending on what kind of properties you want your glass to have)
• If recycling, then you need broken glass.
• Others block, yokes, Paddles, Heat shields
Now it’s time to blow
Raw materials are mixed in the right proportion to form the batch (silica, pot ash, lime, soda ash). This patch is placed in the furnace to melt. For this to happen, the batch should be subjected to temperatures of at least 2000 degrees Fahrenheit (about 1,100 degrees Celsius).
When the batch has melted, the blow pipe is dipped into the furnace while turning it to collect the molten glass. The collected molten glass is then rolled over a steel plate (marver) to center it. The other end of the blowpipe can be cooled off with a barrel of water. This is the time that the glass blower, or the gaffer blow through the pipe. When he/she is not blowing, the open end of the pipe is capped so that hot air doesn’t get out so the glass. If the blower still needs more layers of glass, a gathering iron can be used to get more glass or the blower can dip the glass end of the pipe into the melted batch.
There are several tools that are used while shaping the glass. Heat shield and paddle are used to prevent the craftsman or the blower from extreme heat. The paddle also doubles up as a smoothening tool. The tweezers are used for manipulating the shape of the hot glass to craftsman’s liking. During this process, artistic skills of the blower come into play in terms of shaping, coloring, and adding decorative patterns.
While working on the glass it can reach a point where it is not shaping anymore. This is the time to take it back to the fire through a reheating chamber called glory hole to re-soften. A blower can do this anytime he/she feels it is becoming had to manipulate. Once some shape is formed the glass is moved into a solid gathering iron (punty). The punty has hot gas on its tip to help break off the piece from the blowpipe.
After the right shape is achieved, the glass is placed in an annealing oven to helps it cool properly. A pyrometer is used to measure the temperature. The piece will take about 12 hours to fully cooled off but this is dependent on the size and dimension of the piece. The oven helps the glass to cool without losing its scattered but rigid molecular structure thus preventing it from breaking.
Once the piece is cooled, it is almost ready for use. It will be kept in a cold shop where other finishing like engraving, grounding, polishing, and other details are done. Artist could also etch or relief sculpture to enhanced sophistication.
All the above processes need a lot of care since there are risks involved. Sometimes the glass can crack, explode, there is the risk of burning as well as the toxic gasses that come out from the glass batch. Protective clothing and devices are essential for all the blowers.