Blown glass looks like a pretty modern art form. It's delicate and colorful, and clearly takes modern tech to create. Right? Actually, glassblowing dates to the first century B.C.E., when craftsmen learned how to heat glass so that it could be shaped, molded and made to look like just about anything you might want to imagine. And if they can do it, so can you. Glassblowing is something that almost anyone can learn how to do it. And just think how many people will be blown away if you do!
A History of Glass Shaping
Essentially, glassblowing is performed by softening the glass using heat and then blowing air through a tube into the softened glass. The glass can be spun and moved in order to achieve its desired shape.
When glassblowing was invented by Syrian craftsmen more than 2,000 years ago, molds were used to create different shapes. These early glass creations were usually shaped like clusters of grapes and shells. They were exported to the Roman Empire, where they spread halfway around the world.
Called gaffers, derived from the word for blowers, these craftsmen soon perfected their techniques and began shaping glass without using molds. The basic technique of blowing glass hasn't really changed in the last couple of thousand years.
How to Shape Glass
To shape glass, it must be heated until it has the consistency of molasses. This is called metal. The metal is gathered up on the end of a hollow pipe. Now, air can be blown through the pipe. The pipe can be spun and moved. The glass is swung, rolled and shaped through air and movement. A smooth iron or stone surface can be used to support the glass during the shaping process.
Once the main body of the glass is shaped, additions and extras such as handles and stems can be shaped individually and attached through welding. The glass is sometimes worked with hand tools while it's still soft.
Pro glassblowers don't just shape glass. First, they make the glass.
Glass is made with silica, or silicon dioxide. It's more common name is sand. You need high-quality sand in order to make quality glass that can be used for blowing. But sand alone has a high melting point and isn't easy to work with all on its own. This is why you need to add other ingredients to the sand. Many glassblowers use metal oxides to create workable glass.
Soda, or sodium dioxide, along with lime (calcium oxide) is also added to the sand and metal oxide. The amount of each ingredient in the recipe varies. Various oxides are also added to the mixture in order to create colors. Add just a little gold oxide to create a bright red, or a touch of chromium to get a vivid green.
Tools and Equipment
All the ingredients for the glass are placed inside a crucible, which may be called a pot. This will go inside the furnace. The furnace must reach more than 2,000 degrees F in order to melt the ingredients and create hot glass. That's an extremely high temperature, which is why a glassblower's workshop is known as a hot shop.
Glassblowing is typically performed by an entire team, rather than a single individual working alone. The lead glassblower is known as the gaffer. Once the glass is melted and ready to go, the gaffer dips a blowpipe into the crucible of the furnace to remove a hot ball of glass. The blowpipe is about four feet long, hollow and made with iron or steel.
The opposite end of the blowpipe is dipped into water to cool it. The gaffer then blows through the tube to put bubbles in the glass. When the gaffer is not actively blowing into the pipe, that end of the tube is capped to prevent hot air from escaping through the tube and thus cooling the glass too quickly.
More layers of glass can be added using a gathering iron. However, the gaffer can always dip the end of the blowpipe into the melted glass again to grab more this way as well.
The large, flat surface where the glass is additionally rolled and shaped is called a marver. Glassblowers often also work with a block (a wooden shaping tool) and a jack (a bladed glass shaping tool). Because the glass has been super-heated, it's necessary to use paddles and heat shields to protect the blower from the heat while the glass is being worked. The paddles can also be used to shape the glass.
A metal rod, known as a pontil, is also used to hold the blown glass in place as it is being shaped. This leaves what is known as a pontil mark, which is polished away once the glass has cooled and hardened.
Even expert glassblowers who move quickly often cannot finish shaping the glass before it has cooled past the point of no return. This is when the glass cools enough to harden and become unworkable. This is why glassblowing furnaces also have a glory hole, which is a second furnace. The glory hole is a round, insulated cylinder where the glass can be suspended at the end of a rotating blowpipe. The glass rests on metal supports known as yokes. Here, the glass heats until it's soft enough to work again.
Finishing the Glass
Glassblowing furnaces actually have a third furnace in addition to the main furnace and the glory hole, the secondary furnace. The third furnace is called the annealer or sometimes, the lehr. This furnace is used to slow the rate of cooling the glass goes through, which keeps it from crystallizing.
A pyrometer is used to measure the temperature while the glass is in the annealer, where it is carefully cooled over a long period of time. Once the glass has cooled in the furnace, it still needs to be finished. Next, it's taken to a cold shop. This is where the glass is polished, ground, engraved, enameled and finished in various ways to make it a beautiful piece of art.
What Looks Easy...
If you see a glassblower at work, it truly is an art. The graceful movements, the confidence, it's mesmerizing. It's also a little deceptive. Glassblowing when done by a master looks almost like it's easy. You just learn some techniques, get the right tools and start to work on learning this art. And while it is possible for an amateur to learn how to become a pro with the right amount of time and motivation, there is also something important to know: glassblowing is dangerous.
Glass may crack or shatter if the temperature isn't exactly right. It can even explode, sending dangerous and damaging shards throughout a workspace and possibly into human flesh. And since the material that's being worked is extremely hot, skin, clothing and hair may also be burned with just a simple little slip or the tiniest little clumsy movement.
Then there's the toxicity. Since glass is made up of heated metals and sand, it sends toxins into the air. Over time, this can cause respiratory problems. Glassblowers must wear safety glasses, protective clothing, face masks and respirators. Even with all proper safety measures being followed, accidents can happen to anyone.
Glassblowing is an incredible art form and it's possible to truly make anything out of glass. You can experiment with different colors and create patterns. There's really no limit to the artistic possibilities. But it takes time to learn how to work with glass and it's a pretty dangerous business, so you want to go slowly and work your way through the process. Use the right tools, wear the right safety gear and be prepared to spend some time learning this art.
You can also experiment with some more modern glass-shaping methods. More recent glass artisans have turned to flameworking to shape glass using blowtorches. Glass cutting is also practiced by artisans. And glass casting, which uses molds to shape glass, is still being practiced. This is the oldest form of shaping glass.