I have recently completed testing the firing of ArtGlass Clay in a Paragon Magic Fuse microwave kiln. I am happy to report it works great. Firing takes 5 minutes or less and it is truly amazing. A conventional kiln will take three hours and then cool down time. The kiln is $150 and you can use any old microwave. Dedicate the microwave to crafts. It is probably not a great idea to use it for cooking once the microwave kiln has been used. I tested in an 800 and 110 watt microwave and they both worked fine.
#1 Prepare your glass and dry it completely.
#2 Use shelf primer on the bottom of the Magic Fuse or you can buy fiber paper from Bullseye Glass or any glass supply house. The advantage of using the paper is that you will get a very smooth surface on the bottom of your piece. The disadvantage is that it turns to powder during the firing process and has to be replaced every time you fire. Shelp primer can be purchased at the same glass supply house. It is inexpensive and can be applied thick enough to sand to a smooth surface. The primer comes as powder and and you mix it with water to a creamy consistancy. Brush it on the bottom of the kiln with a wide paint brush. It does not have to be done everytime you fire. Sometimes opal glass will stick to it and lift some off. Clean your piece with a stiff brush and soap and water. Vinegar may help desolve the shelf primer on you glass. If a piece of glass removes a spot of primer, give the kiln floor a fine sanding and re-prime. Make sure the primer is dried before you use the kiln.
#3 Put your glass clay masterpieces in the kiln so that they do not touch each other. Set the microwave on high for one minute. I have fired up to five pieces at one time. I suggest that you start with one piece in the kiln until you have mastered your kiln and microwave. Practice with a piece you have not spent a lot of time creating. this first step is basically just heating up the kiln.
#4 After the minute, open the microwave and lift the lid of the kiln. Not much should have happened yet that you can see. What you are doing is giving any heat applied to the surface of the glass a chance to soak into the glass while taking a look at what is happening in the kiln. You also want to rotate the lid of the kiln so that any hot spots created will be in a different place for a more even firing. In the first minute, you will not see any hot spots but they are starting. Don’t leave the kiln open longer than a few seconds to avoid thermal shocking the glass. Close the kiln and microwave.
#5 Fire the microwave on high for 45 seconds. Repeat opening the kiln and rotating the lid. Doing this quickly will not dump too much heat out and will allow the heat applied to absorb into the glass before the next “blast”. Close it back up and set the timer on high for 30 seconds.
#6 Repeat step five, with the timer at 30 seconds as many times as it takes to see the glass clay turn black. the carbon is burning out of the clay. After a few more 30 second blasts and rotations of the lid, you will see the color come back to the ArtGlass Clay colors. Keep blasting at 30 scond intervals and rotating the kiln lid until your piece is as shiney as you want it. You may set the timer at 15 seconds if you are looking for just a little more shine toward the end of the firing. You can over fire in 10 seconds so go slowly. You will quickly get a feel for the timing as you get more experience with your microwave and kiln. I suggest you keep a log of how many segments you fired and what happened during each segment.
#7 When you have reached the level of shine you desire, take the kiln out of the microwave and keep it closed for 15-20 minutes or until the glass is cool enough to touch. This allows the glass to cool slowly and to anneal and will avoid thermal shocking the glass. Thermal shock is a too rapid cooling of hot glass. The glass will break.
#8 The two things that can go wrong are developing hot spots in the kiln and thermal shocking the glass by leaving the kiln open too long. If the glass is glowing red on one side only, leave the kiln open until the red starts to go away. Don’t forget to turn the kiln lid everytime you blast it with the microwave. Even heat is alway a goal. Don’t thermal shock the glass by leaving the kiln open too long-just until the red starts to go away. You want to give the glass a chance to absorb the heat without crusting over on the surface from too much heat too fast. You may want to leave the lid off on purpose to see how long it takes to thermal shock and break. Be aware that it may start to stress and crack later after it is handled.
If you have any more questions or if your experience is nothing like I am describing, let me know! The kiln is available on my website or your local Paragon distributor.