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Topic: Hotpot for glass fusing, some questions!  (Read 51472 times)
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Little owl
« on: September 24, 2011 03:21:35 AM »

Hey there!
I was really hoping very much to find some people that have experience with glass fusing in the mini microwave kiln that is called the Hotpot.

I have some questions about it, that I would like to find answers to before I buy it! Cheesy (lol, the hotpot really makes me enthusiastic)

Here are my questions, I hope someone can answer them Smiley :

1)  is it possible to use old glass, found in second hand stores and such, will it work? I would love to recycle glass instead of only buying expensive glass. But I do not know if special glass is used, or normal glass.
I am thinking about different things.
Like for example colored marbles (that would be cool), old pieces of stained glass, pieces of old glas plates or whatever really Smiley as long as it is real colored glass and not painted on the outside.

2) is it possible to inbed metals? Like silver, for example (silver clay)

3) is it possible to put several pieces inside the hotpot at once? Or can you only fuse one piece at the time? (there are big hotpots too, which looks use full but only if its possible to put several pieces inside. I don't want to make big things, only pendants and such) On the picture below several pieces are placed inside, but when I watch youtube tutorials.. people always only put one piece inside, so this made me wonder.

4) is it possible to work with enamel powder? There are really pretty pearl colored, or gold etc, enamel powders and it would be interesting if those could be put between two pieces of glass for example.

5) and my last question.. does it really work? haha Smiley I mean, does the hotpot really give good end results? Or is a real kiln needed for that?

For the people that never heard of it before, a hotpot is a stone mini kiln that is placed inside a microwave, which will heat up in a very short period of time, so much that glass can be melted/fused.

Here an example of something that is made by fusing glass that way (not made by me!!)
« Last Edit: September 24, 2011 03:25:05 AM by Little owl » THIS ROCKS   Logged

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« Reply #1 on: September 24, 2011 08:11:54 AM »

I can't answer specifically about the hot pot, but here are a few suggestions about glass fusing.

"1)  is it possible to use old glass..."
--Special glass (Bullseye COE 90 is what I use) is best. You can be certain that the glass will all fuse nicely without cracking. Commercially used glass or glass that you find in shops, sea glass, etc., are all chemically different. Combining these glass may not work and may result in cracking. That said, glass from a specific source (say a gin bottle or a single piece of stained glass) will fuse to itself--meaning, you can take pieces from a single source, put them in your hot pot and it will fuse together.

"2) is it possible to inbed metals..."
--Maybe. You can use metal inclusions, but expect some bubbles. Too many inclusions may result in cracking. Glass artists use something call high fire wire fused between piece of glass to make hangers, some use them for decoration. Metal foils or leaf will also work. Silver clay would probably have to be fired first, but I'm not sure.

"3) is it possible to put several pieces inside the hotpot at once..."
--With any kiln, you will need kiln wash and/or fiber paper under your glass piece or pieces. Always allow between 1/4 and 1/2 inch between pieces since they tend to spread when fusing.

"4) is it possible to work with enamel powder..."
--I'm not sure about enamel powders, but I think they would not work. There are many colors of powder frits and mica available to use in fusing.

"5) does it really work..."
--I know people who hate hot pots (aka microwave kiln) and I know people that love them. Have you searched the craftster glass community for the terms hot pot and microwave kiln? I know it's been discussed in the past. Also, I've noticed that people who use microwave kilns tend to have a special microwave that they only use for their kiln. This is probably a good idea since some commercially available, old glass, and metal inclusions may have lead in them and it wouldn't be good to pollute the microwave you use for cooking. Most, if not all, glass specifically made for fusing (Bullseye, Uroboros, Wasser, etc.) do not contain lead and are therefore food safe.

Good luck!


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« Reply #2 on: September 28, 2011 03:42:14 PM »

Welcome to the world of glass fusing, its addictive!

I'll add a little to what CrazyEyeGlass said.

1) You can use  - and fuse - any kind of glass, but not all glass is created equal. As CrazyEyeGlass pointed out, most people doing kiln fusing use glass with a 90 COE (Coefficient of Expansion). Stained glass is normally 96 COE and lampworkers use an even softer glass at 104 COE.

The problem with fusing 'found' glass is that you have no idea what the COE is. Some commercial glass bottles can be very hard glass (borosilicate is sometimes used, and that has a COE of 38) , and if you mix glass types they are almost certain to break when you fuse them. This is because each type expands and contracts at a different temperature, and if you put differing-COEs together they will be cooling and heating at different times, most often not in harmony.

So, by all means, play around with glass bottles and stuff, but remember to only work with bottles on their own, or with regular bulllseye-compatible (90 COE) on its own and don't mix the 2.

2) Yes, you can imbed metals, but the wire will create bubbles as the piece is heated, so unless you want bubbles for artistic reasons then you're going to have to do one of two things.
Either you'll need to drill through the worst of the holes with a dremel or some other drill once the piece is cooled, and then refire. Or, when you make the piece, put some small clear glass chips in between the different layers, around the outer edges of the piece. That way, when the piece starts to melt, the glass in the middle (containing the wire) will fuse first, and the resulting gasses will be forced to the outer edges of the piece, hopefully to escape before the whole piece fuses.

3) I don't really know anything about a Hotpot, but as CrazyEyeGlass points out, you'll need to prepare your kiln furniture first. Or spend a day minutely chipping melted glass off of soft ceramics.

Ask me how I know..... 0_o

4) Enamel powder is simply very fine glass, so its totally possible to use it while fusing. You'll need to make sure that its COE is compatible with the underlying glass, but other than that, the world is your lobster.... ;-)

Glassline make a great ready mixed liquid enamel paint, if you find that easier, and frit can be bought at varying grades - from chunky to powder. You can even make your own.

Its fine enough that it can get into your lungs and make you really, really sick.

Like lung transplant sick. So do it!

Anyway, hope this helps, and good luck!
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« Reply #3 on: January 22, 2012 04:18:23 PM »

I received some stained glass shards and played with them in the kiln.  For the opaque colors I ended up with a film, it appears the glass was coated.  That also happened with some clear window glass, so beware of possible coatings.  I could take some strips the clear glass and make them into beads, they turned out ok but not spectacular.  It is fun to play with recycled glass but I ended up with to much crackage, especially since I have a manual kiln and have to watch it closely.

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« Reply #4 on: January 22, 2012 06:01:43 PM »

That film is probably devitrification and is the result of improper annealing. Finding the proper annealing temperature will take some experimentation.

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