Microwave Kiln Uh-Ohs and How to Deal with Them!

Fuseworks Microwave Kiln Fused GlassWe all make the occasional “oops”, that’s why Diamond Tech is here to help. Keep in mind that practice makes perfect and if you follow the instructions and these pointers for preventing and sometimes fixing a fusing flub, you’ll be churning out awesome art in no time!




Arg, I have air bubbles under my glass!

Make sure the layers are laying flat. Edges fuse before the center, so cut your base glass 1/8” larger than the top layer to      allow air to escape.

Err, my edges are uneven!

Uneven edges generally occur if you didn’t fire it long enough or to a high enough temperature for a full fuse, continue firing in 30 seconds intervals to reach desired effect.

Oh, no! My edges look like a porcupine.

The piece was fired too long. The spiked edges are caused by the glass grabbing as it is trying to shrink.

My glass is toooo flat!

Again over firing is the culprit. Reduce your power and shorten your time. After your first firing inspect the piece, continue firing in 30 seconds intervals to reach desired effect.

I wanted a different size!

Glass naturally reaches ¼” thickness when heated. Your glass will shrink or expand to obtain this depth.

My glass is repelling.

This happens when different coatings like dichroic and iridized coatings are fused together. To avoid this, encase the coated glass with separate non-coated glass.

There’s a white gunk on my glass.

This can happen if your glass remains between 1000ºF-1300ºF too long or by cleaning glass with a slew of cleaning products; clean your glass with diluted vinegar or water.

My edges are gray and scummy, gross!

This usually happens when a piece is fired once and then cold worked before refiring. Cold working involves using either a grinder or glass saw on a piece of glass. Scrub completely after cold working and dry before refiring.

My piece has cracked!

This can happen from thermal shock or glass incompatibility. Thermal shock happens by exposing the hot glass to cool air to soon or by heating too quickly (an “S” shape appears). If the crack occurs where two pieces of glass meet, the two pieces are not compatible. Make sure your glass has the same COE (coefficient of expansion).

My glass has shattered, much like my hopes

Don’t give up yet! Pieces over 1” with more than 1 layer may sometimes shatter. Make sure your glass is clean and dry and fire at a lower power.


If you have any questions, please ask away in our comments section, we would love to hear from you! Check out our Creative Corner for more how-to and a flurry of fun fusing projects.

13 thoughts on “Microwave Kiln Uh-Ohs and How to Deal with Them!

  1. Ann Sutphin says:

    Love my microwave kiln but I have one problem that keeps popping up. I get a gray almost ashy look between layers of glass. Its almost as if I have fired the dicro too long and the surface is turning to ash. Is this something I am doing wrong? I have not seen anyone else with this problem and I do not think its devit because it is never on the top of the glass only between layers and not all over just in spots.


    • Diamond Tech Crafts says:

      Hello Ann,

      Thank you for contacting us on WordPress, we are glad to hear you love your Fuseworks Kiln! We would love to help you, but we need some more information. Can you give us an idea of your fusing process; What do you clean the glass with (glass cleaner, alcohol, paper towel, terrycloth towel)? Do you use anything to adhere layers of glass? Are you using pre-cut circles? A photo would help a lot as well. Any information you can give us would be great!

  2. Kathi says:

    I melted the plastic know for the turntable and have ruined my microwave. I use the large kiln so wonder if the turntable is necessary?

  3. Ronna Hochman says:

    My brand new moicrowave kiln seems to havea hot-spot. Pieces on one side melt much faster than on the other. Why does this happen, and how can I fix this?

    • Diamond Tech Crafts says:

      Hi Ronna,
      Hot spots in the kiln generally only occur after extended use. Hot spots can actually develop in your microwave as well and the position of the kiln in the microwave may cause a hotspot, using a turntable reduces the chance that a hot spot will affect your kiln, but still may not prevent a hot spot from affecting your kiln if it not positioned correctly. To check if your microwave has any hot spots, remove the turn table, if present, and place several cups or small bowls of water in various areas of the oven, set for 1 or 2 minutes and check every 30 seconds, if any of the cups boil faster, thats where your hot spot is. If you find a hot spot using this method, adjust the placement of the kiln. If you do not find a hot spot in your microwave, please contact customer service at craftinfo@dticrafts.com.

  4. Rhonda says:

    I am loving my microwave kiln! However, after many uses, the base is bumpy and uneven. My pieces are requiring more grinding on the back side to make them smooth. I am wondering about repairing the base. I have heard of some paste that can be used to rebuild the base. But I’m not sure which kind to use. Or can I just sand the base a little bit? I don’t think its bad enough to need to be replaced.

  5. RIRI says:

    I’m fusing with an extra large microwave kiln.
    The kiln paper turns dark….
    A funny smell appears….but the glass never fuses…
    Does not melt at all.
    Have put them in a smaller kiln, and they fuse perfectly well…
    No smell…no kilnpaper turning black.

    Is my extra large kiln damaged ?
    I see no kracks in it….or missing pieces….

    Please help.

    • Diamond Tech Crafts says:

      We are so glad you are getting positive results with your small microwave kiln!
      Unfortunately we can’t help you troubleshoot your issues with the Large Microwave Kiln as we do not sell this product and this must be from another manufacturer. We do recommend contacting that manufacturer to assist you.

  6. Yumi Coyte says:

    I’m a complete newbie and after only several attempts, quite successful ones, I fired my microwave kiln too fast too high and melted the glass and kiln paper well into the surface of the kiln. Is there any way to fix this or is this the end of my microwave kiln? Please advise. Thank you very much.

    • Diamond Tech Crafts says:

      Dont Worry Yumi, all is not lost.
      Some people have found ways to do some slight repairs to the kiln base that you may be able to find online, but for the sake of having an even fusing surface and the stability of the kiln we recommend ordering a replacement kiln base. They are on our site HERE or you could contact customer service at (813) 806-2923 or sales@dticrafts.com and they would be able to help you.

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