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Kiln Pointers

Memories of a Kiln Repairman “Down Under”


This is the Roman pottery that Linda Gray mentions below.

David Coggins shares valuable pointers on element repair, preventive maintenance, and cleanliness in the ceramic studio.

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Memories of a Kiln Repairman “Down Under”

By David Coggins

Queensland, Australia

ELEMENT TWISTERS

Some kiln users repair burned-out elements by twisting the broken ends together. After unplugging the kiln, they use a small gas torch to heat the two ends to red heat and twist the wire together with pliers. This rarely works for long, because the element has a protective oxide coating after many firings. The oxide coating not only protects the wire from further oxidation (or burning away), but it is also a good electrical insulator, so the connection made by twisting is electrically poor. The poor connection will not conduct current very well and will get extremely hot during the firing, most likely burning out again.

On very rare occasions if you are lucky, the wire gets just hot enough to weld itself together without melting, thus making a good connection. Usually the twisted joint burns out near the end of the firing when the kiln is hottest, so the user gets "just one more" firing out of the element. The faulty element is then promptly forgotten until the next firing, when it is too late to call a kiln technician, so the process is repeated and so on.

These sorts of spot burn-outs in elements are usually caused by poor kiln house-keeping--not regularly vacuuming all the bits of clay and glaze that collect in the element grooves. One little spot of glaze on an element has a "fluxing" action on the wire. (That is, the glaze causes the wire to melt at a lower than normal temperature.)

A collection of dust in the bottom of a groove can cause a localized overheating of an element. Both of these conditions will cause a premature failure of the element, usually with a little ball of melted wire at the point of failure.

I have seen kilns with dozens of these "temporary" element repairs. The users were lucky to get one good firing every second or third attempt due to all the element failures. This was very poor economy; wasting all that power just to avoid the cost of getting the kiln repaired properly. It also had another very undesirable side effect: Every time the twisted element failed, it caused an electrical arc, which melted some of the element wire into the brick groove. By the time I was called to repair the kiln, so much element wire melted into the brick that it would have to be dug out, damaging the element groove and creating a weak spot where the element would not be held securely.

The moral of this story is to use only the element twist repair as a real emergency measure, and be sure to call a kiln technician to replace the faulty element straight after the firing. Better still, keep the kiln element grooves clean, and avoid the problem in the first place!

DUST UP

One of my pet hates while visiting studios to repair kilns was clay dust. Most studios were very clean and aware of the risks of dust, but I visited a few exceptions.

Probably the worst I ever encountered was a commercial studio that cast large urns and vases. They had several large electric kilns that required regular attention. Unfortunately, the kilns were near the cleanup area, where the worker fettled off the mould marks and sanded down large greenware pieces. He would then blow off the dust with a compressed air gun, all the time unmasked and with a cigarette dangling from his mouth. Several times I had to make quick exits to allow me to breathe. When he was in full flight, I had trouble seeing him for the dust. I shudder to think what the inside of his lungs must have been like. He is probably very ill by now.

Another ceramic "studio" I visited was in a country area on an acreage property. The studio was originally in a large shed behind the house. The shed became full of moulds and casting gear, but instead of building another shed for cleaning, glazing and firing, they simply moved those operations into their house. The cleaning and glazing were done in the kitchen and dining room, amongst the food and crockery and cutlery. The kiln was in the lounge room, right beside the sofa and stereo. I didn't get to see where they slept, but that was probably a good thing.

Everything in sight was liberally coated with dust and glazes. They were living with dust 24/7 and probably ingesting glazes with their dinner. I don't think they will live long.

It always amazes me how people are terrified of asbestos and ceramic fibre and the risks of smoking yet think nothing of living at least 8 hours a day (or 24 hours in the case of our friends above) completely surrounded by a cloud of fine clay (read silica) dust. Sometimes I was reminded of the Peanuts character Pigpen; as he walked about, a cloud of dust followed him.

Moral of this story: Clay contains silica. Dry clay contains free silica. Silica in the lungs causes silicosis. Silicosis causes illness and premature death. Always work in a well-ventilated area and/or wear a dust mask. Always clean up the work area of dry clay powder. Be kind to your lungs-- it is hard to breathe without them!

Cheers for now - have a good Easter!

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Thank you, David, for the kiln pointers.

READER RESPONSE

Charles Fulks of Southington, Ohio wrote, “My wife works with stained glass and glass beads. My hobby is ham radio. She works on one side of the rec room and I have my ‘ham shack’ on the other. Our hobbies really make for some ‘togetherness.’ By the way, the quality of your kiln is to be commended.

“The wife gives away everything she makes as gifts,” he wrote. “Costs a fortune, but she is happy. Makes for a happy marriage.”

Two weeks ago I wrote about an ancient pot that I found at Leptis Magna, Libya. Linda Gray of Tulsa, Oklahoma wrote, “About 10 years ago I was with a group touring Israel, and archeologists excavating in Caesarea Phillippi let us scrounge through their pile of small pottery shards. I came away with a 5” piece from a wheel-thrown Roman urn.

“As a potter,” Linda wrote, “I instinctively placed my hands as if I were throwing the pot on a wheel and discovered that my hands fit perfectly. Obviously that Roman potter nearly 2,000 years ago was similar in size to my 5' 3" frame. Also, his fingerprint remains inside where the handle was pressed onto the pot. This piece is my favorite piece of pottery that I own.”

You can see a photo of Linda’s pot by visiting www.paragonweb.com and selecting “Support,” and then “Kiln Pointers” from the drop menu. Or click on this link (or paste it into your Internet browser window):

http://www.paragonweb.com/Kiln_Pointers.cfm

Last week I mentioned the Factory Tour at Paragon’s website. (The tour is under “About Us” on the site.) In addition to the article above, David Coggins wrote, “I particularly enjoyed looking at your photo gallery of the factory. It reminded me of the trip I made to Paragon in Texas for the 2002 kiln seminar. I really had a great time at the seminar. It was all too short. I was fascinated by the factory and all the methods used to make the kilns, probably more so because I was repairing and rebuilding kilns myself at the time.”

Wishing you a happy Easter,

Arnold Howard Paragon Industries, L.P. - Better Designed Kilns

2011 South Town East Blvd.

Mesquite, TX 75149-1122

Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646

ahoward@paragonweb.com / www.paragonweb.com

PRIVACY NOTICE: Under no circumstance do we share or sell your email address.

Copyright 2006, by Paragon Industries, L.P.



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