A moment ago a friend sent me an email describing some shelves that exploded inside his kiln. They had been wet before he fired them. His experience prompted me to send out a list of kiln safety guidelines. Wet shelves are covered in point #12 below.
1) Do not leave the kiln unattended during firing. Check the kiln from time to time. Observe the normal sounds that it makes and length of firing time. Once you are familiar with the normal operation of your kiln, you will know when something goes wrong.
2) Keep the lid closed when the kiln is not in use. This keeps dust out of the kiln. Also, should someone turn on the kiln while you are away, the closed lid will keep the heat safely inside the firing chamber.
3) Never place anything on the kiln lid, even when the kiln is idle. If people become accustomed to placing papers and other objects on the kiln, they may forget and do that while the kiln is firing. During operation, the lid may get hot enough to burn combustible materials placed on top of it.
4) Remove all tripping hazards from around the kiln. Keep the kiln's supply cord out of traffic areas.
5) Do not let the cord touch the side of the kiln, which may damage the cord.
6) Avoid extension cords.
7) Do not remove the ware from the kiln until the kiln has cooled to room temperature. It is possible for thermal shock to break hot ceramic pieces. The sharp edges of broken ware can injure hands.
8) After firing glazed ware in your kiln, examine the shelves for glaze particles. Sharp slivers of glaze stuck to the shelf can cut hands. Before rubbing a hand over a shelf, be sure the shelf is free of glaze shards.
9) Fire only approved materials purchased from a knowledgeable supplier. Do not fire marbles, pieces of concrete, rocks, and other objects. Rapid heating to high temperature can cause violent reactions in many materials.
10) Greenware, which is unfired clay, must be bone dry before firing. Moist greenware can explode inside the kiln, damaging the ware and the kiln. Place a piece of greenware against the inside of your wrist. If it feels cool, it is too wet to fire.
11) Do not fire cracked shelves. They can break during firing, damaging the ware inside the kiln.
12) Store kiln shelves in a dry area. Moist shelves can explode inside a kiln.
13) If you smell burning plastic, turn the kiln off. Examine the wall outlet and supply cord for signs of burning.
14) Never place extra insulation around the kiln in an attempt to conserve energy. The extra insulation can cause the wiring and the steel case to over-heat.
15) Do not wear loose-fitting clothing around a hot kiln.
Wishing you success in all your firings,
Arnold Howard Paragon Industries, L.P. 2011 South Town East Blvd. Mesquite, TX 75149-1122 972-288-7557 / 800-876-4328 Fax: 972-222-0646 firstname.lastname@example.org / www.paragonweb.com