Tuesday, December 29, 2009

Microwave Kiln - QUESTIONS & ANSWERS - Part 2

Anonymous said...
How wonderful you are doing this blog, just when I'm getting into using my little Fuseworks kiln. I have a "big" programmable kiln for use with PMC, but bought the microwave one to save on electricity. It seemed a fine way to do a few dichro cabs for my PMC work. Anyway, I've been running into the problem of one layer slipping off/alternately cracking into several pieces. I've been using dichro with a base or top layer of black or clear (same COE). I even tried one single piece of dichro with no top or bottom layer, and it still cracked in half at 4 min. I have an 800 watt microwave with a turntable I bought at a yard sale for $5, and have been running the fuse for 3 to 4 minutes with the turntable disabled as per kiln instructions. Sometimes when I look at 3 min., it's not done, and put it in 30 seconds more per kiln instructions. So, does glass thickness have anything to do with it? Should I use a fuseable glue to hold the pieces together? Is the highest setting too much and should I back off on the highest power? Does the extended time period have anything to do with any of my problems? Some of my pieces have come out fine, but most are not. I'm spending a lot of time in trial and error, and that can add up with dichro. Sorry, lots of questions, but no answers readily found. I enjoy using the kiln, but want more consistent results if possible. Thanks so much.

Designs by Sylvanye Glass Studio said...
Happy you found my site, and will be more than happy to help you resolve your problems. First, I must ask if you know that the microwave you purchased is indeed an 800-watt. Unless you were given the manual that came with the microwave or it is indicated on the unit itself it may not be an 800. Higher wattage and depending how much higher this could be part of your problem. However, let say, it is an 800 watt then this is what needs to happen:


Note: If glass heats up to hot to fast it will crack.

• Create your design with no less than two layers of glass.
• Pre-heat your glass for 2 minutes at 70%. This will allow your glass to heat up slowly and evenly; otherwise, it will crack.
• Next, without opening your microwave door, turn your dial to 4 minutes on High (your microwave oven automatically reverts back to High). Then open and peek briefly at your piece (a rush of too much cold air can cause your piece to crack).
• From this point start adding in 30-second increments until you get the desired look.
• Add the total minutes and seconds up to give you the total Fusing Time; this does not include the 2 minutes warm-up.

Notes:
1. DO use your turntable. Despite what you and I have both read, you do need the turntable. Glass wants to be evenly heated just like in a regular kiln and the turntable helps to ensure this.

2. A “cold spot” in your microwave kiln’s top (hood) can also cause your glass to crack. A “cold spot” is where a chip of the black granite is missing thus not allowing the heat to reach that specific area causing not only uneven heat distribution but also the design facing that spot to not fuse properly.

Yes, glass thickness, the type of glass, the number of layers, etc. in the MK has an affect on how long it will take to completely fuse a design.

Your glass slippage is generally due to unbalanced layers of glass. Heat pulls or draws glass and if it is unbalanced will draw that unbalanced piece down and away.

The glue you are using is probably fine but, if it is not completely dry, your piece will crack.

Follow the instructions I have given you and you should be okay, assuming it is an 800-watt microwave.
Recap:
• Warm-up 2 minutes at 70%
• 4 minutes on High
• Gradually peek and add in 30 second increments
• Do not remove the MK from the oven without venting it for at least 10 minutes. This can cause shock to your glass also.

Looking forward to hearing from you with positive results.

“Sam”

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