How to Fuse Glass in Your Ceramics Kiln

Have you ever tried to fire glass in your school kiln? I once actually unloaded 550 unfused glass pieces because I chickened out. However, after I researched, took a class, and finally took the plunge, I realized I had nothing to be afraid of! If you’re in the same boat, repeat after me, “Worrying is like a rocking chair. It gives you something to do but gets you nowhere.”

I’m here to tell you: Glass firing in your ceramic kiln is easy.

This is especially true when you realize most of the crazy in-depth glass fusing guides are designed for serious glass artists. If you’re an art teacher and want to fuse hundreds of student pieces at a time, you don’t need to get complicated. You can get fancy once you are comfortable.

So, let’s get comfortable.

Before you start firing your glass, check out my article, Simple Steps and Supplies to Get Started With Glass Fusing,” to help you decide what supplies you need to buy.

How to Fire Glass in Your Kiln

glass ready to go in kiln

First, figure out what type of fuse you want.

1. Tack Fuse: 1350-1370° F

At the lowest temperature, tack fused glass will just “stick” together and maintain many of its characteristics (including relief and edges). As the temp goes up, the glass loses its relief and hard edges. This type of fuse is good for detailed projects.

2. Medium (Contour or Soft) Fuse: 1400-1450° F

A medium fuse is a high-temperature tack fuse. It’s perfect for student work because all the edges will come out rounded, and therefore, be safe for students to touch. It’s also a good bet if you want to keep some relief in the work. This is the type of fuse I use the most in my classroom. 

3. Full Fuse: 1460-1470° F

Full fused glass happens when the glass is heated long enough or gets hot enough to completely join the glass together. Full fused glass is completely smooth and glossy with no texture. The edges are soft and any corners are rounded. You can see a comparison between medium fuse (on the left) and full fuse (on the right) in the image below.

medium fuse and full fuse

Then, set up a firing schedule.

If you fire clay, you most likely use cone firings. Cones are firing schedules with predictable outcomes: cone 4 gets you bisqueware, cone 5 gets you glazeware. Easy-peasy lemon squeezy!

If you want to play around with glass fusing, you cross into the territory of programming your own firing schedule. (AHHHH!) But really, it’s easy. Firing schedules you program yourself are called Ramp-Hold firings. You are telling the kiln to ramp up to a temperature at a certain rate and hold there for a set amount of time. Each time you tell it to do this it’s called a segment. Most schedules have about six segments.

Here is some vocabulary that is helpful to know.

  • Ramp: To raise or lower to a temperature
  • Rate: The rate of degrees/hour at which temperature rises. You can have it go slow, like 100 degrees per hour, or much, much faster. 9,999 degrees per hour is the fastest and is often called FULL.
  • Hold (also called Soak): How long the temperature remains the same
  • Segment: Each segment includes a ramp, rate, and hold

Your kiln’s digital controller will have a page in the manual for you to set up a firing schedule. Look there first. However, many kiln companies also have customer service number if you’d like to talk to an expert.

Here are 3 easy firing schedules I’ve tried with success.

Download the sheet below if you’d like to keep it for a reference!

firing schedules

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Decide if you will vent.

You are probably used to venting your kiln with every firing. The noxious fumes clay and glaze give off make it a necessity. However, with glass, it’s a different story. Glass does not release fumes when fired. Most glass artists actually do NOT vent their kilns because of the risk of thermal shock. Thermal shock happens when glass cools too quickly, which can cause it to crack or even break.

Because of my ceramics background, I still choose to vent my kiln when firing glass. The kiln paper and glue may have trace amounts of noxious byproducts, and I like to play it safe. You can read more about venting your kiln here and make the decision for yourself!

glass in a drawer

Test it out.

Before you fire student work, test out your kiln with a few pieces of your own. Be sure to place each piece a few inches away from other glass pieces (and the edge of the kiln shelf) to prevent them flowing together or right over the edge!

Enter your schedule into your kiln and press start! The results will amaze you. Just remember glass holds heat for a long time, so even if your kiln temp is low, hover your hand above the glass pieces to see if they’ve cooled before touching them.

Keep an eye out for the next article in the series about teaching your students how to create using glass!

If you’ve ever fused glass, how did it go?

If you’re trying it for the first time, share your results!

Kelly Phillips

Kelly teaches elementary TAB in Hopkinton, MA . She strives to create an environment where all students can become independent, self-directed risk-takers.

Related

  • C. Files

    Great read! I have fused in my kiln before and it took a lot of trial and error to figure out how hot I needed it to get to make it fuse. I’d like to try it with my students in the future as I have a beautiful kiln with a vast amount of ideas and abilities!

    • Kelly Phillips

      Awesome! Let me know how the firing schedules work for you!

  • Marin Acuff

    I would LOVE to try this, but I’m only at my school with the kiln for 3 hours a day so I’m already nervous to leave it running using clay.

    Do you know if this schedule would work the same way with my manual kiln?

    • Jessica

      I have not taken the plunge into glass because I have a manual kiln! It may not be as hard as I imagine it to be to figure out heat settings, but I only have numbers on my dials – 1-6 to gauge the heat in manual kiln.

      • Dina S

        We did a fundraiser (Square 1 Art) and paid for a computerized kiln box and its installation. We can easily fuse glass now. Wouldn’t recommend doing it with a manual kiln. Good luck!

    • Kelly Phillips

      I wouldn’t fire glass in a manual kiln and would definitely try and get a digital box installed. Does anyone have any advice for this issue that had a manual kiln they use for glass?

      Thanks Marin!

  • Carlos McDaniel

    A colleague told me that kiln wash residue on the furniture caused her glass projects to get a matte finish. How can I avoid this?

    • Jessica Gregory

      Kiln paper can be fired and works like kiln wash

      • Kelly Phillips

        Thanks Jessica and Carlos for your responses! I love that people are exchanging ideas here.

  • Lauren

    I’d love to try this! How do you load it in and keep it from sticking to the kiln shelves?

  • kat

    What type of glass are you using? How do you know if the glass is compatible?

    • Kelly Phillips

      Hi Kat! In the article there is a link to the previous article all about what to buy. Thanks for the question.

  • Helen Snyder

    I have chickened out on this, we have a manual kiln I use for clay and the occasional glass blobs (looked great as water in our bird baths). I actually took a class and have a new jewelry kiln I found but haven’t turned it on. One problem is space and the fact I teach K-8 in same room – my worrying rocking chair :) I need to get an expert in here. Maybe I’ll bribe a local artist with wine and coffee ;) Great article and inspiration!

    • Kelly Phillips

      I get it, Helen! It’s hard to take that first step. Maybe start by making your own artwork, piloting with one class, or taking a class at a local studio. The birdbaths are super fun for clay/glass starter project so you’re totally on your way!

      Thanks for the feedback!

  • Katie Stewart

    I learned how to fuse glass last year and have been teaching it to 4th,5th, and 6th graders. They make necklaces, magnets, earrings and pins. I love how every student is able to successfully make something they are proud of.

    • Kelly Phillips

      That’s awesome, Katie! What kind of findings did you use for your jewelry? High temp ones that are fired in the kiln? Or ones you glued on after? I’ve been experimenting with both and the kids seems to like the glued ones better.

      Thanks for the feedback!

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