The Saga of the Microwave Kilns

Glass Working
#1

So. We had a class using the microwave glass-fusing kilns.

Kiln #1 – 3 small pieces, about 1.5-2" each.
Ran for 10 minutes, then 1 minute more. Good fusing, and all edges rounded to some degree.

Kiln #2 – 1 medium piece, maybe 2.5"
Ran for 10 minutes – totally fused.

Kiln #3 – 1 medium piece, possibly 2.75" – heavily layered.
Ran for 10 minutes, plus 3 minutes at 1 minute per. Some fusing, some square edges.

So, since I now had two pieces with square, sharpish edges, I went to re-do them. Plus, I had figured out that there’s a hot spot on the edge of the kiln.
Kiln #3 – 2 medium pieces, placed on the edge of the kiln that’s on the outside edge of the microwave plate. Since one of the pieces had run for a total of 13 minutes the previous day, I figured 11 minutes would be fine, especially since I now had 2 pieces of glass in there. Nope.

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Both pieces were fully fused, since they were both in the hot spot. One had … run… There was minor excitement while I figured out what to do about that.

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#2

Moving forward, maybe the full circle should have the fire paper and the hot spot marked with an underglaze pencil?

#3

It’s not so much that the kiln has a hot spot – it’s where you put it in the microwave. Evidently the microwave has a hot spot.

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#4

Do the microwaves have turntables or do you remove those for using the kiln in it?

#5

You keep the turn table in.
Beth, did you let the microwave cool down anytime between Firings? Im think a few min cool down will help keep the microwave from burning out.

The microwave is only about 3 months old, odd it would ha e a hot spot but it is possible. I’m thinking the kiln May have a thick spot of ink in a small area, Causing it to not fire even. But that is just a guess.

Hopefully we will be able to test the 1700w microwave soon.

#6

It was completely the next day. Microwaves tend to have hot spots, as they usually emit microwaves from one place. That is why they put turntables in the things. Glass just tends to show the spot more than your dinner does…

And, I had realized that there was a “sweet” (hot) spot during the class. I’d put kiln wash on the kiln, and I wanted it to be a bit drier before we put the kilns in with the glass. I heated just the base for 30 seconds. There was a round spot (on the edge that was on the edge of the turntable) that was completely dry, where the rest was still damp. I took advantage of that knowledge in placing my glass for the second round. And, hoo-baby!! That was damn effective!!

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