Glassblowing is a unique art form that requires not only a creative mind, but physical strength and dexterity. It became very popular in the 1960s when the Studio Glass Movement lead to glass artists working in their own studios, similar to ours. Glassblowing is seen as a mysterious and magical process and we frequently get asked questions about it. We put together this blog post to give you an idea of the basic studio setup, tools and the process of glassblowing. We hope it’ll inspire you to try glassblowing yourself!
Furnace: Our furnace consists of a tank that can hold about 800lbs of clear glass. It runs 24/7/365 and is kept between 2000 and 2400 degrees Fahrenheit. The furnace is made of high temp ceramic castable and it takes about 6 days to reach the correct temperature, so if it ever goes out, we’re out of commission for a few weeks! We also have a smaller 200lb furnace, which is used for special orders that require colored glass. Glass takes a while to melt, so furnaces allow us to keep a great quantity ready for use at all times.
Re-heating Chamber: We have two reheating chambers and one is the largest in Michigan! Reheating chambers are kept at about 2100 degrees Fahrenheit and are turned on about an hour before they need to be used. Our smaller chamber is our workhorse and we only use the large one for special projects as it uses a lot of resources and requires more assistants with a high level of skill. Reheating chambers are necessary for continually reheating the glass to keep it at a working temperature so it can be manipulated.
Soda-lime Glass: We get our soda-lime glass from a company called Spruce Pine, that is located in North Carolina. The glass arrives in a raw material, called batch, and it has to be put into the furnace to melt. The process of filling the furnace and melting batch is called a charge. Because we have such a large furnace, this is a long process that takes about 12 hours to compete to melt about 1,000lbs of batch! While the batch melts in the furnace, it takes on an acidic quality and eats away at the interior of the furnace, so the furnace has to be rebuilt periodically.
Annealing is the gradual cooling of the glass down to room temperature. Our annealing furnaces run on a computer program and the length of time for pieces the size we tend to make is about 16 hours. Larger pieces take a longer period of time in the annealer.
There are different types of annealing ovens. Ours is an upright with four shelves. An alternative is a top-loading annealer, which opens like a cooler and pieces are placed inside.
Annealing is necessary because if glass is not gradually cooled down, it can go into shock, resulting in breakage.
Tools are extremely important for a glassblower. While working at the bench, they will almost always have a tool in hand to work the glass. The image below shows just some of the tools that are kept on the bench. We’ll take a look at each of them and how they are used.
Tweezers: Tweezers used for glassblowing are just like other tweezers, but larger. The pointed tips are used to stretch and pull hot glass.
Jacks: Jacks look similar to tweezers but larger and they have a springy handle. This allows the glassworker to control the space between the blades to manipulate and change the shape of the glass. Jacks can be used in a variety of ways. The blades can be used to shape a vessel as it’s being inflated. If the blades are held close, they can help to create a constriction to separate the glass from the blowpipe. They can also be used to create an opening of a vessel. If they are flipped around, the straps on the jacks can also be used for shaping glass. The video below shows how the jacks are used to push the glass up the pipe.
Standard Shears: Straight shears are metal tools used to cut through hot glass. Some modern shears are embedded with chips of industrial diamonds.
Tagliola (The Tag): The tag is a square-shaped knife used to shape or sculpt hot glass. They come in different sizes and have both sharp and rounded edges to allow for a variety of shaping surfaces.
Soffietta (Straight & Bent): A soffietta is also called a puffer and it can be either straight or bent. The bend allows the glassworker at the bench to blow into the piece they are working on without the help of an assistant. After glass has been removed from a blowpipe, a soffietta is used to allow for further inflation. It can also be used to blow air onto glass to cool down a specific portion of glass.
Diamond Shears: Diamond shears are scissors with a diamond shaped blade. They are used to cut glass and their shape leaves less of a tool-mark than straight blades. They also have a notch on the end that can be used to grab a pipe.
Wooden Paddle: A paddle is a wooden board with a handle that can be used to shape glass. They can also be held by an assistant to shield a glassworker from the heat of the glass.
Punty Rod (top): A pontil or punty is a solid metal rod that is tipped with a bit of hot glass and used to hold glass while a piece is made.
Blowpipe (bottom): A blowpipe is an iron or steel tube used for blowing glass. One end has a mouthpiece that is blown into and the opposite end has a metal ring that holds gathers of glass.
Marver Table: A marver is a smooth, flat surface – usually a stainless steel table – that glass is rolled on while attached to a blowpipe or punty rod. The marver allows the hot glass to be shaped and also cools it down, which can also aid in creating shapes as the variations in temperatures of the glass will affect the shape, especially when it’s blown into. Marver is French for "marble".
Block: A block is a tool made of wood that is used to shape and smooth molten glass before it is inflated. They are kept in water, which creates a layer of steam when it touches the glass. Keeping them soaked in water also extends their lifespan and prevents them from sticking to hot glass. The shape of the block is designed to give you a uniform template to shape your glass. Blocks come in a variety of sizes and as the glass you’re working with gets larger, you will increase the size of your block.
Optic Molds: Optic molds are metal molds made of cast aluminum or brass, that glass is pushed into to create texture on the outside of the glass. They come in a variety of shapes, sizes and textures to create different effects on blown glass.
Creating a glass piece all starts by taking a gather of glass. A blowpipe or punty is taken off the piper warmer (shown in the left image below). The pipes need to be hot for the glass to stick to the metal.
The pipe is taken to the furnace and dipped into the glass to get the first gather (shown in the video below). That gather is taken over to the marver and and the glass is rolled on the surface. The marver provides a smooth, even surface to shape the glass and also helps to cool it. Cooling specific areas of the glass helps to force the air bubble to go to a certain part of the glass or for the glass to expand in a specific way. Throughout this process, the pipe must constantly be turned; if movement is stopped, the glass will be overtaken by gravity and start to drip down like taffy. The glass is also taken to the reheating chamber several times. Each time the glass is heated up, it is called a flash. Flashes are used to heat up specific parts of glass or to even out the overall heat.
The video below from The Corning Museum of Glass gives a brief history of glassblowing and shows a demonstration of the process explained above, which is used to make a simple vessel.
When a piece is completed, it is taken over to a knock-off table. It is removed from the pipe and a hand-torch is used to melt any pontil marks. Last, the glass is placed in the annealing oven to cool for at least 24 hours. The video below demonstrates this part of the process.
You can see that glassblowing is a really unique and captivating art form that takes years to master. It lends itself to limitless creativity and pushes the boundaries of what an artist can create from such a turbulent medium. This post only covered the very basics of glassblowing, but there are so many great resources for you to learn more- we’ve listed some below. We’d also be happy to answer any questions you have in the comments!
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Tools & Equipment: