What is the Difference Between a Glass Kiln and a Ceramic Kiln?

So, what is the difference between a glass kiln and a ceramic kiln? 

Glass kilns are used for working with glass, and ceramic kilns for working with ceramics, so you would think they are not interchangeable. 

Well, it’s not that straightforward. 

I’ve had this question about kilns a few times now, so I thought it was about time I did some research and published this article. 

Processing Temperatures 

A major difference between glass and ceramic kilns is their operating temperature. Glass kilns don’t need to fire up to the same temperatures as ceramic kilns.  

Typically, we process glass somewhere between 600 C (1100 F) and 815 C (1500 F). The lower end is used for processes like slumping into moulds, and draping over formers. We go even lower to fire on low-temperature decals. The higher temperatures are used for processes such as full glass fusing, raking, and casting. Of course, there are exceptions to this, but it’s generally around that range. 

Now, I must say that I am not an expert in ceramics, but I do know that the temperature range for processing ceramics is quite broad. It stretches from the lower temperatures we use for glass up to around 1315 C (2400 F). The moulds you typically purchase for glasswork are bisque-fired ceramic. That’s done at temperatures around 1,050 C (1900 F). 

So, what does this mean? Well, it means that while you could in principle process glass in a ceramic kiln, you couldn’t fully process ceramic items in a glass kiln. It just doesn’t get hot enough. 

But your ceramic kiln will need a temperature controller so you can regulate the segments. Or you need to test and test until you can do it manually. Sounds like a lot of work to me. 

Element Positioning 

In both glass and ceramic kilns, when you’re processing your work, the evenness of heat is a major factor.  

This means that the positioning of the kiln elements is especially important. Glass kilns generally have elements at the top of the kiln, while ceramic kilns have the elements on the sides. 

The main reason glass kilns have their elements at the top of the kiln is because of the nature of most glass fusing projects. They involve heating a project that is substantially flat. If you think about it, most projects involve firing pieces of glass that are flat, such as fusing together pieces or heating a piece until it softens and slumps or drapes over a former. Because we want to heat the piece evenly, right across the surface, the best place for the elements is then at the top of the kiln directly over the piece. 

With ceramics, the requirement is much the same. You want the pieces to be heated as evenly as possible. But ceramics are quite different, in that they are more 3D in nature. And often they are stacked in several layers in a kiln for efficiency. So, to achieve even heating of these layers you need the elements to be on the sides of the kiln. 

Of course, like most things, there are exceptions to this. Some glass kilns have elements on the side, some ceramic kilns have elements at the top. 

Some glass projects, such as casting, work better with side elements to heat the mould evenly, rather than just the top surface. 

Dual-media Kilns 

If you don’t have any kiln, but would like to work in both media, there is now a range of dual-media kilns that can be used successfully to process both glass and ceramics. 

With the flick of a switch, you can change from glass to ceramic mode. 

These kilns also have the depth required for the 3D nature of ceramic projects. It allows for taller pieces, as well as the stacking of multiple pieces. A downside to this is that when in glass mode you will need to elevate the shelf closer to the top element.  

Another issue with dual-media kilns is the life of the top element. In ceramics mode, the top element of the kiln is not switched on. When you have elements in an operating kiln that are not on, the life of those elements can be shortened. Just how much I don’t know. But that may be acceptable if you have a need for one of these kilns. 

Summary 

So, if you’re thinking of using your glass kiln to fire some ceramics, you’re probably thinking of making some moulds, which are bisque fired. Well, if your kiln fires close to something like 1,050 C (1900 F), you probably can do it. Depends a lot on the type of clay you’re using. The only thing to consider is that taking your kiln to its max is hard on your kiln and will shorten its life. To me, it’s not worth it. 

When it comes to firing glass in a ceramic kiln, your options are much better, as long as you can control your kiln well. You still need to fire in appropriate segments. 

To get around the position of the elements, for either glass in a ceramic kiln, or ceramics in a glass kiln, you could just fire the kiln slower. This gives the glass or ceramic project more time to achieve an even heat. 

Raising your glass higher in a ceramic kiln is the least of your worries. There are many options available for this. 

So, like all things, it’s not black and white. It does depend on your situation and what you are thinking of doing.  

If you have a good ceramic kiln and want to delve into some glasswork, then you’re in luck. But if you have a glass kiln and want to make your own moulds, I suggest it’s not worth the wear and tear on your kiln. 

If you’re just thinking of buying a kiln, buy to suit your needs.

Don’t buy a ceramic kiln if you’re primary need is for glasswork, but there’s an off chance you’ll want to do some ceramic work in the future. If you have a solid intention of working with ceramics as well, that’s different, but then you should be considering a dual-media kiln.

I hope this has been of help.