Table of Contents

Click on the question and you'll be taken to the answer.

How do I decide what kind of kiln to buy?

Can I use any kind of glass in a kiln?

How can I make my fused glass look more unique?

Do I have to wear a face mask when working with glass?

What's the best way to drill holes in stone or glass?  See: Bench Tips Page

More questions and answers to come in the future

How do I decide what kind of kiln to buy?

        It seems that there are a lot of people out there who are interested in more information about buying kilns. I didn't cover kiln purchase in my handbook, because the book's information starts the minute you get your kiln. So here's some more information regarding kilns: 

        When you get the Surefire Handbook, you'll find in it a list of all the ancillary equipment you'll need to set up your own operation. If you haven't done this before, I urge you to take a class to make sure it's something that you really want to get into. It's a wonderful hobby, but it can get expensive. You're not just going to need a kiln; you'll need kiln shelves, kiln wash, special viewing glasses, miscellaneous other items, and, of course, lots of glass. Glass is pretty expensive in and of itself.
        
        My general rule is: if you're really serious about this and you want to do bowls, plates, and possibly larger pieces, you should invest in the biggest kiln you can afford, because you'll quickly get frustrated with the size limitations of small kilns. I started out with a manually-operated kiln, which helped me to get a real sense of how the glass performed under heat. I don't think you get that with a computerized kiln. But manual means that you have to hang around to check on the glass, and manually adjust the controls. This can be a long procedure. If you've got the bucks, you can't beat the ease of use of a kiln with computerized, programmable controls. But if you can't afford a computerized controller, don't let it keep you from fusing glass. I didn't get my first computerized kiln until I was fusing glass for several years.
        
        One of the important factors that determines the best kiln for you is whether you'll have a 220-line available or you'll only have 110.  My first kiln was the biggest I could get using a 110-line, and I still have it, but it's REALLY slow--it takes about 6-7 hours to get up to a full fuse temperature. Having a 220 dedicated line really helps--for medium to large kilns it cuts the heating time by 40-50%. But, if you don't have a 220 line, there are still options. Just make sure you, or someone who understands electrical things, reads the specs on the kiln that you want to buy to make sure that your line is adequate to meet the amperage demands of your kiln. Even for my first kiln, I had to install a different outlet on my 110 line.

        Most people agree that an 18" diameter kiln is a good size to start with, if you can afford it. That size will give you the freedom to do large plates, or a decent number of smaller items. Keep in mind, though, that you don't usually stack glass on multiple shelves for firing, as you do with pottery. It's just one layer.

Mini-kilns

        Many people's budgets aren't large enough to buy an 18" kiln, and if you're one of those, you might want to consider purchasing a mini-kiln. These kilns have 6", 8", or 9" interiors. They have several obvious drawbacks: They can only be used to fuse small items--larger plates, bowls, and vases are out. Some of them have rheostat dials (like on a stovetop), but the least expensive mini-kilns lack control dials and have to be turned on and off manually to control the rate of heat increase. This means they have no governor, and can burn themselves (and anything around them) out if you don't keep an eye on them.

       However, mini-kilns have three advantages over larger kilns: They heat up much faster, so you can complete your fusing in a much shorter time; they allow you to view your glass much more closely because the kiln sits on a counter or bench top instead of the floor; and they cost a fraction of the larger kilns. Glass behaves in mini-kilns much the same way as it does in larger kilns, only it does it faster, and at somewhat higher temperatures. So you can learn on both. And, with a mini-kiln, you don't have the huge investment to lose if you decide that fusing is not for you. Mini kilns can look like miniature ovens with doors on the front, or they can look like white "beehives" where the helmet-like cover holds the heating elements and lifts off the base. Be sure to comparison shop about these the same as you would with larger kilns.

What to look for in a regular-sized kiln

        In terms of medium to large kilns, the thing that distinguishes a glass kiln from a pottery kiln is that glass kilns have heating elements in the underside of the lid (very helpful when fusing flat items or getting even heat across a slumping platter). It's these very elements that limit the temperature that you can build up inside a glass kiln--about 1700 or 1800 degrees F., max. (as opposed to 2300-2600 degrees in a pottery kiln, whose heating elements are in the sides and not the top). Once you go above about 1900 degrees in a glass kiln, you start damaging those heating elements in the lid, because heat rises.

        The placement of the lid elements is crucial. Before you buy, inspect the underside of the lid to make sure it has an evenly-spaced pattern of heat coils: You want even heat production across your glass surface, without any hot or cooler spots. Some larger kilns have both lid and side coils, which increase the speed of heating. I suggest that you check out the websites of the major manufacturers (Evenheat, Paragon, Skutt, and AIM) and do some comparison shopping. Call friends or acquaintances who own kilns and ask them what their favorites are, and why. You're interested in how quickly and evenly the kiln heats, how long it works without repair, and, if it has computerized controls, how accurate they are.

The issue of depth

        Also, keep in mind that oftentimes these companies will custom-make a given model deeper than advertised. All it takes is adding one more course of fire brick, not a big deal. If the model you're interested in has heating elements in both the lid and the inner walls; you can possibly expand the depth. Why be interested in depth? Because you don't put the glass on the floor of the kiln--you have to put it on a ceramic kiln shelf, which has to be elevated at least a half-inch off the floor. And, the glass should not be any closer to the lid of the kiln than two inches. So, you're losing three inches of height--at least--even before you start. In shallower kilns, this will limit the height of the mold that you can use. This is not a problem if you just want to do plates, but many folks like to do bowls and even small vases, so they need more height. Realize though that if you're buying a kiln with heating elements only in the lid and not the sides, too much depth will take it longer to heat. It's a tradeoff.

Looking for a good used kiln

       You might also want to check out used kilns so as to get a larger model for your money. But I'd advise checking the kiln out in person:
1. Plug in the kiln and turn it on HIGH. Then open it up and look at the coils. If they're not all glowing evenly within a couple of minutes, you might have to replace some coils. It's not that expensive and you can do it yourself, but you might not want the hassle.
2. Arrange with the seller to take the kiln on a trial basis. Then, you can set it up, and if it has a controller, you can set the controls and run it and watch and record times and temps. to make sure that it's heating at the rate that the programmer says.

Several other kiln-buying suggestions:
        1. Look up the manufacturer's web pages (Evenheat, Paragon, Aim, etc.) for a list of dealers in your area.
        2. Call local stained glass shops (this is also a good place to find out whether anybody local is selling their kiln--you might get a good deal on a used one).
        3. Check your local classified ads under "Crafts." You might just be surprised!

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Can I use any kind of glass in a kiln?

Theoretically, you can fuse any glass to itself, i.e., cut it into pieces and layer it for fusing. Early fusers used window glass and bottle glass that they developed chemical ways to color. But, you have to make sure all the glass is identical, so window glass should come from the same manufacturer and be all of the same type. If you mix glass, you're risking damage to your kiln, because the different types of glass will expand and cool at different rates, which can result in cracking, and possibly, a small explosion that could damage your heating elements.

Glass manufactured especially for fusing is assigned a C.O.E. (Coefficient of Expansion) number, so you know it's safe to fuse if you use glasses with the same C.O.E. number. The most common C.O.E. for fusing glass is 90.

Stained glass which is not clearly labeled for fusing is, unfortunately, not a good candidate for your kiln, unless you're just slumping one layer of it over a mold. Even then, it's a risk if it is a multicolored glass. This is because those beautiful streaks and swirls of different colors have a different chemical structure than the colors next to them, and as a result, a slightly different C.O.E. I've tried combining fuseable and regular stained glass made by the same manufacturer, and my fusing tests indicated too much internal stress to be safe. Just because a piece doesn't crack right away doesn't mean that it won't ever crack. Some folks test their finished pieces by putting them in the top rack of their dishwasher and running it. I wouldn't recommend this with a fragile piece or one that's made of coated glass (iridescent or dichroic).

I recommend that beginning fusers buy all their glass with the same C.O.E., 90.

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How can I make my fused glass look more unique?

Here are some suggestions for things you can do to make your glass look special:

1. Create your own designs based on your favorite things, from flowers to sports, Asian art to marine mammals. If you use a computer, you can download clipart, or clip and scan in picture elements from magazines or even your own photos. You can then copy these elements into your favorite paint program, and then manipulate them to make your own original design. (Or, you can build an abstract design by combining the geometrical shapes you can draw on a computer program). Print it off and enlarge it on a photocopier until it's the exact size you want, so you can use it as your template for cutting your glass. [Of course, you can do all this without a computer, by cutting, arranging, and pasting up your own design template.]

2. Play with unusual color and texture combinations in your glass. Experiment first with smaller items; when you hit on something that you really love, make it again as a bigger piece.

3. Look for fun and interesting molds, or, if you do pottery, make your own out of clay that you bisque-fire and then paint with kiln wash.

4. Invest in accessory glass:

    --stringers (angel-hair pasta-thin rods of glass). These can be glued on with tiny bits of white Elmer's glue to hold them in place before firing. You can also bend them by heating them in a candle flame--this takes practice--be careful! Texture fuse stringers to retain their shape; full fusing results in lines of color.

    --frit (tiny bits of glass, ranging in size from pea-sized nuggets to tiny grains). Frit is especially good for texture-fusing because then it doesn't lose its shape. Full-fusing frit results in colored blobs--which might be the effect you want. Texture-fused frit adds a splash of color and pebbly surface to your glass piece.

    --powders. These are literally powdered glass, and can be applied in the same way that enamels are applied on metal--they can be sifted or painted on, giving you all increased color possibilities and painterly effects.

    --lusters. These are my favorites. They look like shiny eyeshadow colors and in fact are made of the same non-toxic materials. They can be mixed with a fixative and painted onto the glass. The higher the fusing temperature, the better they stick. They have to be on the top surface, exposed to the air.

    --for other ideas and accessory materials, see my Surefire Handbook. 

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Do I need to wear a protective face mask when working with glass?

The short answer is YES, which might surprise some stained glass people. I started out doing stained glass and used a glass grinder for years without wearing a mask--because no one told me that I had to--then, suddenly, I developed an alarming sensitivity to it.

I did some reading and learned that when you use a motorized glass saw, grinder, or drill, you're usually also using water. So what's happening while the motor is running is that microscopic bits of glass are adhering to tiny droplets of water vapor, spraying out and floating up--your nose. You know why asbestos insulation has been outlawed in schools--so people don't breathe in microscopic bits of glass, which is part of asbestos. Similarly, when you use motorized grinding, sawing, or drilling equipment for glass, you're getting a dose of inhaled glass--not good at all for your lungs.

Because of the water vapor, using a carpenter's dust mask is not good enough. You have to use a mask whose label says it is designed for protection against vapors. I suggest you skip the paper-type masks and invest in a good plastic face mask that has adjustable straps and two filters--one on either side of the nose area--that you can change. These are available from large hardware stores, or jewelry supply companies. Also, don't forget that those glass-filled vapors are also floating up into your eyes, so always wear glasses of some type when you grind, saw, or drill glass.

Yes, I agree, it's a pain to wear these. But in the long run, your lungs will thank me.

 

More questions to come in future weeks...e-mail me with yours!

 

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These pages are authored by Dr. Judith Kiriazis, who retains ownership of all information in them. Printing of this page for personal reference, one time use, is permitted. Any other reproduction is expressly prohibited without written consent of the author. Copyright 2003-9.

Copyright © 2003-9  [Judith Kiriazis, Heart of Stone Studio]. All rights reserved.
Revised: 11/09/09.

 

 

 

 

 

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These pages are authored by Dr. Judith Kiriazis, who retains ownership of all information in them. Printing of this page for personal reference, one time use, is permitted. Any other reproduction is expressly prohibited without written consent of the author. Copyright 2003.
Copyright © 2009  [Judith Kiriazis, Heart of Stone Studio]. All rights reserved.
Revised: 11/09/09.