Microwave kiln & microwave

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    Has anyone ever ‘burned out’ a microwave oven using this type of kiln ? I have used a brand new microwave for fusing purposes only, I’ve done 64 fuses & at first the time was about 10 min for a full fuse..now its getting to be 40 min ( !!!) so I’m returning the oven & hopefully will get a replacement. I’ve been fusing mostly at 100% power. Any ideas on fusing times & power levels so I don’t  burn out my next oven ?

    Much Thanx


    My experience is with a large Hot Pot microwave kiln and an old 650W microwave oven at full power. I did not count the number of firings but I guess between 200 and 300 – definitely more than you have experienced. Mine is also taking longer to do its fusing and is geting worse. I also vaguely recall reading somewhere on the Internet that microwave kilns “wear out”. From this I assume our micowave kilns have reached the end of their useful lives.

    I suspect the dark coating inside the microwave kiln (this bit that absorbs microwave energy and re-emits as thermal energy) deteriorates (oxidises?) over time so becomes less effective. I believe it is possible to re-coat microwave kilns but I have not tried it.

    Mine has developed thermal expansion/contraction cracks so now heats up unevenly. Again a re-coating might resolve this at least temporarily.

    Firing times were usually about 8-10 minutes, but now are taking longer and longer (currently about 40% longer). I couldn’t fire any faster with my 650W microwave oven but comments I’ve read on the Internet suggest that higher wattages can cause thermal shock problems with the glass.


    Thanx for all your info. Seem that the problem was the microwave itself as the kiln worked fine in another microwave. As you mentioned, I think the wattage was also too high so the ext oven I get will bbe lower wattage.

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