Maryanna at the Paragon factory visually checking the glass.
Firing The Microwave Kiln
Recent Q&As: Firing crystalline glazes without a controller
Kiln Story: The Melted Ice Cubes
FIRING GLASS IN THE MICROWAVE KILN
Recently I have been experimenting with a microwave kiln, which fits into a standard microwave oven. The kiln fires so rapidly that after five minutes, there is barely enough time for the outer surface of the kiln to become warm. Meanwhile, the orange, glowing kiln interior is hot enough to fuse glass.
I have had consistent firing results with this kiln by checking the glass visually before it has fused completely. That is the method I have used for years in firing the little Paragon QuikFire kiln.
The microwave kiln is very difficult to fire by recommended time alone. This is because microwave ovens of the same wattage can have different firing times. Also, firing times can vary even in the same oven. One afternoon, the firing time was 10 minutes. The next morning in the same microwave oven, it was 5 minutes, 30 seconds. This was due to voltage fluctuation.
Here is the method I use to fire the kiln:
Set the microwave timer for a longer period than you will need. If firings take about 5 minutes, set the timer for 6 or 7.
Load the oven. Press Start. After a few minutes, open the door and lift the kiln top an inch for a second or two. Lower the top. Close the door and press Start again. (Note: You must wear clear safety glasses to check the glass. That is essential. Also, stay about an arm's length away from the kiln while you check the glass.)
A minute later (or 30 seconds, depending on how far along the glass has heated), repeat the above. As the glass gets closer and closer to final fusing, check it more often. When the glass is done and you remove the kiln from the microwave, write down the time shown in the display window. Subtract that time from the number of minutes you started with. That is your total firing time.
I have found that heat distribution varies inside the kiln unless you use the oven's turntable. If you do not use the turntable because the vibration and movement shifts the glass pieces, then fire only one or two pieces at a time.
Q. My wife wants to try a crystal glaze. After it is fired to 2165F, the glaze needs a temperature hold of 3 hours at 1950F to develop crystals. How do I do that with a manual kiln that uses a Kiln Sitter?
A. Crystalline glazes can be fired in a manual kiln, but you will need to sit with the kiln during the 3-hour hold period. You will also need a pyrometer.
After the kiln reaches 2165F, turn off the switches. Allow the kiln to cool down to 1950F. Then raise the Kiln Sitter weight, press the plunger, and gently lower the weight. Turn the switches to Medium. If the temperature starts going back up, turn the switches down.
Watch the pyrometer and adjust the switches to maintain a temperature of 1950F. This is a balancing act. As the temperature drops a little, raise the switch settings; as the temperature goes too high, lower the switch settings. This won't require constant attention once you get the feel of it. You can read a book while the kiln fires.
KILN STORY: THE MELTED ICE CUBES
During the 70s, my supervisor at Paragon designed a calendar. One of the pages was to be illustrated with the headline “Cold feet, warm heart.” He made a huge pair of earmuffs from a band of stainless steel and fake fur and placed them on top of the kiln. He poured bags of ice on the floor around the kiln.
Just when we were set to take the picture, we discovered that we were out of 120 film for the Mamiya camera, which was perched on a tripod in front of the kiln. All we had was 35 mm. The ice was melting, so we scrambled to find the 35 mm camera, load it, and mount it on the tripod. We shot the photo just in time.
I hope you have a relaxing weekend.
With best wishes,
Arnold Howard Paragon Industries, L.P. – Better Designed Kilns 2011 South Town East Blvd. Mesquite, Texas 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 firstname.lastname@example.org / www.paragonweb.com
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