Friday, November 8, 2013

Kiln Maintenance


There are several types of kiln insulating materials, brick and ceramic fiber being the most common for use in firing metal clays. Most ceramic fiber kilns are called muffle kilns and this is the kind of kiln I have. Muffle kilns heat up faster than the brick type and can easily be moved from classroom to classroom without damaging the kiln. It's best to not move the brick type kiln because movement can cause the bricks to become loose since they are often held together with mortar.


Over time, the muffle can develop cracks. I've been told that the cracks shown here in my kiln were caused by opening the door while the kiln is very hot. I'm guilty of this, due to opening the door while enameling. These types of cracks are not harmful. As long as the muffle isn't breaking apart into pieces, and the elements are still secure inside the muffle. As the muffle heats up it expands and the cracks close.
You should occasionally inspect your kiln by checking the thermocouple in the back of the kiln, making sure it sticks out from the back of the kiln at least 1/2". It can sometimes inadvertently get pushed into the muffle. The thermocouple measures the kiln's temperature and sends this information to the kiln's computer. If it is pushed into the muffle, it can't accurately measure the temperature inside the kiln.




If you are having problems with melting your metal clay while firing, then you should test the kiln temperature for accuracy with a kiln tester. Here is a link to my instructions on testing.








Sometimes the door's latch needs adjusting. The latch should lightly catch so that it doesn't shake the kiln. The door doesn't need to close tightly against the front of the kiln. There should be some space for the door's material to expand as the kiln heats. If you work with enamels, you don't want the door to shake the kiln when closing, otherwise you may find your enamel has fallen off your piece! On my kiln the door latch adjusts by twisting a screw on the latch.





It's also good to check the kiln's plug wires making sure they are not cracked or damaged.  If they are, seek advice from a kiln repair company.

Until next time have fun claying around.


 

by Janet Alexander
Technical Advisor

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