Let’s Talk Glass!

Some of the results of a week of intensive glass fun.

So, a few months ago, at the end of April, I learned how to make glass. It was more geared towards a studio setting, but there’s plenty of knowledge to be had and damn it, I’m still nearly overloaded on it. The reason for that is simple, and it’s the fact that I adore glass. I love it in all it’s forms, in how much you can do with it, and how varied the applications are.

Some of the photos and things I learned there are below. It’s caused some dangerous rabbit holes to start to form, and I can’t wait to see where things go from here.

I’ve been slowly circling back to it as an art form for a while, but this week of experimentation both solidified why it’s what I love as well as opened my eyes to how much else I could possible do with it. Since then, I’ve been reading a bit of Neri’s stuff, and am trying to work on gathering articles about the production of glass in my eras of interest.

I also taught a basic class on glass making at Atlantia’s University. Definitely a first draft of the class, but I’ve got so many ideas for how to expand it out and to make it even better. Much of this post is taken from the handout for that class.

Words to Know as We Move Forward

  • Batch: the mix of materials used to make glass
  • Formers: the majority of what makes up glass
  • Flux: an additive that lowers the melting point of another substance
  • Stabilizers: additives that determine the durability of the glass
  • Coefficient of Expansion: the rate the glass expands for each degree of temperature increase
  • Gather: glass collected directly from the furnace and then worked
  • Cane: approximately pencil-sized rods of glass that can then be used for smaller application

What Is Glass?

Glass is a durable, inorganic, solid material. It’s amorphous/non-crystalline, meaning that the molecules that make it up can be in any shape, not just the organized/lattice pattern that defines a crystalline structure. It has about the consistency of honey when melted. Its durability means that it’s mostly impervious to wear and natural elements, allowing it to be used for any number of purposes, from decorative to household uses.

When we made it, there was just one batch of soda lime, which is what would have been used in the Northern European cultures, and it didn’t quite turn out as expected. The ratios were off, and you got something quite crystalline and chunky.

Whats Glass Made Of?

  • 70% Formers
    • Silica – found in quartz-based sand
  • 20% Flux
    • Alkali (sodium carbonate and sodium bicarbonate) – generally natron
  • 10% Stabilizer
    • Lime (calcium hydroxide)

Where Did They Get It?

Almost all references I found indicated that the glass would have been imported as chunks of glass, or cullet, which is smaller pieces of glass fragments. It would have been imported from the Eastern Mediterranean. This is something that I’m working on in a somewhat erratic manner, and need to put together for the next version.

While local materials could have been used – generally quartz and soda or potash – it does seem to be far less common. I’ve got some things talking about different ash compositions and how they affect glass, but it’s not an article I’ve gotten to necessarily.

Making Glass

Making glass requires a furnace and a crucible, though the necessary temperature varies on the type of glass being made. To melt glass, the temperature is usually about 2000° F, but can be melted at temperatures between up to 3100° F. Modernly, most studios keep the furnaces at about 2100° F to 2200° F.

Glass – batch, cullet or chunk – can then be used in whatever way the artist decides.

Please note – the temperature can vary based upon the actual composition of the glass. Different compositions may require working at a higher or lower temperature.

Because large hunks of glass aren’t as useful to me as a torch worker, several of the other participants most obligingly pulled cane. If you’ve never seen how it gets done, video is below.

At this point, we’ll end for now. I’m trying to be more regular on my updates, I’ve certainly said I would enough, but now… I think there’s a grand plan…. and I can’t wait.

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