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The Creative Can of Beans

This is part two.  It probably won't make sense unless you've read part one.  Click here if you need to bring some sense into your life. 

When we last left our lonely can of beans, we'd emptied the contents, heated the can in the kiln, and the covered the outside surface with kiln wash.  Now we're ready to get to the glass. 

Root through your scrap pile and find a piece of glass that's bigger than the can you're using.  You want a piece that can cover the bottom and extend over the sides as well.  About eight or nine inches is fine for the average can of beans.  (I know, I know, this is is a little large for a piece of scrap, but bear with me.  We'll learn how to use small scraps in a future can of beans tutorial.)

It doesn't matter if your piece of scrap is perfectly square.  It doesn't even matter if it's a circle, a triangle, or even an odd concoction the shape of Alaska.  I like circles and ovals best, but you can try any shape you'd like.  Just about any type of glass works, from baroque and wispy to cathedrals and textures.  Even ordinary window (float) glass can be used.  (Paint on it if you'd like.)  Different shapes and glasses will give you different results.  Experimenting is good.

Is your can cool yet?  Is the kiln wash dry?  If not, just wait a few more minutes until it's ready.  If you got distracted, it doesn't hurt to leave the can to dry for a day or two.  But whenever you're ready, just place the can back in the kiln.  Bottom side up, as before.  Center the scrap of glass on what is now the top (used to be the bottom) of the can.  Since the glass is larger than the can, it will extend over the edges and stick out in all directions.  You can use a ruler if you're really finicky, but absolute centering isn't necessary.  Sometimes the best results come from scraps that are off center.

Once you're happy with the placement of the glass, shut the kiln door and turn it on.  As when you were kiln washing the can, you can fire at a fairly high rte.  You should be able to fire at a rate of at least 10 to 15 degrees Fahrenheit (5 to 8 degrees Celsius) increase per minute, and maybe even faster.  (For those who think in hours instead of minutes, that's 600 degrees Fahrenheit or more per hour.) 

Firing slower is ok, too.  But most of us are impatient and want to fire as quickly as we can.  Fortunately, with one layer of scrap glass we can fire pretty fast.  Thicker glass requires slower firing.  Anyway, keep firing until the temperature reaches around 1200 degrees Fahrenheit (650 Celsius).  It should take about an hour, more or less.  (Maybe you can eat some canned beans while you wait.)

If your kiln has a peephole, now is the time to look inside.  It's best to wear protective glasses.  Not those clear plastic things you wore in chemistry lab (or was that wood shop?), not even those expensive didymium glasses some glassworkers use:  the best glasses for kiln-workers are ones that shield your eyes from infrared rays.  Frequent exposure to infrared rays, which glass gives off once it reaches around 900 degrees Fahrenheit (480 Celsius), can cause cataracts or other eye problems.  To prevent that, wear glasses that block infrared rays.  Welder's #3 lenses (or even # 2.5 or #2) are just about right, and very inexpensive.  Many people claim you can get away without using glasses, but some people think you can eat three-month-old tuna salad, too.  You can, but sooner or later it will catch up to you.  

If you peer inside the kiln (glasses on, right?), you'll see that the glass has taken on a red glow.  The edges of the glass those parts that were extended over the edge of the can of beans may have started to droop down.  If not, just wait.  (Gravity is your friend.)  Holding the temperature at around 1200 degrees will cause the glass to "slump" or "sag" over the can.  Some people call this "draping" because of the way the glass seems to drape around the edges of the can, but the keep thing to remember is that the longer you "soak" at this temperature, the more the glass will droop.

With some glasses, such as "float" or typical window glass, slumping often takes place at a slightly higher temperature (around 1350 to 1400 Fahrenheit / 750 Celsius).  Some people prefer to slump at 1250 and some prefer to slump for a few minutes at a lower temperature (say, 1150F / 620C) and then quickly raise the temperature into the 1300's.  There aren't quite as many different slumping temperatures as there are ways to eat a can of beans, but there's enough variation for you not to worry if your slumping works best at 1250 and mine at 1200.  The key is to learn what's best for your glass, your kiln, and your way of working.

Once you're happy with the way the glass has slumped over the can, you can stop soaking and begin the process of cooling down.  That's the subject of the third (and final!) part of this three part tip.

Click here to go on to the final part of this tip.


Copyright 2005 Brad Walker.  All rights reserved.

This article was originally written in 1999 and became the basis for the Warm Glass website.  It has also been published in Common Ground: Glass, the newsletter of the International Guild of Glass Artists.  There are at least two more parts, all coming soon to a computer near you.

If you want to learn more about fusing and slumping glass, check out the Warm Glass tutorial at www.warmglass.com/basic.htm

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