Tool Tuesday: glass

I guess I don’t generally think of it that way, but probably the most important tool in glassblowing is the glass.

It comes out of the furnace clear, at a working temperature of 2080 degrees fahrenheit. Whether you’re adding color, making something that will fit in the palm of your hand or that will need multiple people to move, each blown glass piece usually begins and ends, in some way, with clear glass.

It’s fluid like honey when hot–and you’re constantly rotating it on the end of a metal rod or blow pipe to keep it centered. Stop for a second and it moves one way, turn it again (perhaps with some heat) and it moves the other.

Easily shattered, yet surprisingly strong, it takes on a whole new life when cool.

Tool Tuesday: the box

“Don’t love it ‘til it’s in the box. Well, actually, out of the box.”

This is something that you learn very early in glass blowing. “The box” is the annealer. Any piece you create needs to make it safely into, and then out of, the annealer. Once inside the box, your piece of glass is slowly and incrementally brought down to room temperature to relieve internal (invisible to the naked eye) stresses within the glass.

A typical annealing cycle at our studio begins at 890 degrees and comes down to 200 degrees over a period of at least 12 hours–making its way to room temperature from there. The thicker your glass, the longer the annealing cycle. This one took a year to anneal.  And if it’s not annealed properly? Your piece will shatter or crack at some point in its lifespan.

Why can’t you love it until it’s out of the box? Well, lots of things can go wrong along the way as you’re making something.

Things can also go wrong in the annealer–from gremlins in the electrical system messing up the cooling cycle to something falling over and breaking. So, it’s best not to get too attached too soon.

Tool Tuesday: keeping it hot

While you’ll never get the glass as hot as it was when it came out of the furnace, the glass does need to be hot for you to work with it. And every second you work with it, it’s cooling. That means you need to reheat.

That’s where a reheating oven, called a glory hole, comes in. Made mostly of steel and refractory brick, with a mixture of gas and air working their magic inside, this is where you reheat all or a portion of your piece as you work. Unlike the furnace, you start the glory hole before each session and turn it off when you’re done. It takes about an hour to come up to working temperature–here’s a look just after the burner has been lit.

And later in use.

Tool Tuesday: the furnace

The bulk of my making happens in the glass studio–often called a hot shop. And the heart of any hot shop is the furnace.

This rather giant furnace lives at DC GlassWorks and Sculpture Studios, a public access glass and metal facility in Hyattsville, Md.

Inside is a crucible filled with glass.

A peek inside the furnace during maintenance. Here you see the crucible before it has been enclosed inside the furnace. After being bricked in, the cover is removed and the crucible itself filled with glass that is then brought up to temperature.

The crucible and furnace at DC GlassWorks holds more than 500 pounds of clear glass. Once it is turned on, the furnace runs 24 hours a day, seven days a week, every day of the year. If the power goes out or something goes awry with the gas and air mixture that keeps things hot, someone needs to check the furnace. It doesn’t matter if it’s 2 am or snowing, the furnace needs to be on.

The glass inside the crucible “rests” (when not in active use) at 1980 degrees fahrenheit. To work (blow glass), the temperature of the glass is brought up to 2080 degrees fahrenheit. As the crucible is restocked with additional glass weekly, the temperature reaches 2300 degrees fahrenheit.

When you step up to the furnace to gather clear glass, it’s a bit like stepping in front of, and then looking into, the sun.

Taking a gather of clear glass from the furnace. Moving quickly is good–it’s hot!

The size of your gather of clear, what you add or take away from it and how you shape it from there are all open to your own design.

The furnace and the clear glass within are the building block.