[Clayart] Death by kiln?

Thu May 12 19:46:56 UTC 2022

One more story.  When I was hired at the Appalachian Center for Craft in 1994, the only wood kiln we had was a two-chamber Bourry-box designed by Doug Casebeer and built by him, Jane Dillon, and her students.  It was the cover story in Ceramics Monthly in the April, 1989.  The primary firebox was built off the left end of the kiln and the secondary one was between the two chambers.  Each firebox was stoked through a door at the front, and the roof of the primary firebox was built with kiln shelves with a layer of hardbrick over that.  At some point in the past, a student had left behind a huge pitcher about 24" tall, and someone placed it atop the firebox.  It looked good and had been there for years with no problems, but the overhead metal roof above the kiln was designed in such a way that in a particular storm, water accumulated inside the pitcher.  No one knew that, and the water stayed there for an unknown period of time, absorbing into the highfired clay.  

The next time we fired the kiln, I was on stoking shift with one of my students.  As the first chamber approached cone-10, and my student started stoking the secondary firebox between the two chambers while I kept stoking the primary firebox.  When cone-10 was down in the first chamber, I sealed up the air holes on the primary firebox.  I finished that task and then went around in front of the kiln by the secondary firebox.  What that means is that neither me or my student could see that pitcher atop the primary firebox.  And what that means is that we were out of the line of fire when the pitcher exploded.  

Pots that didn't fit in the firing were still on a ware cart near the primary firebox.  The shards from the explosion took out all the adjacent windows along the back of the building and smashed most of the pots on the ware cart.  If anyone had been near the primary firebox when that pitcher exploded, they probably would not have survived. I am very thankful that it took so long for enough heat to soak up through the layer of bricks atop the firebox.  

That was the experience that really taught me about the explosive potential of moisture impacted in vitrified clay, and I am very thankful that no one was hurt.  
- Vince

Vince Pitelka
Potter, Writer, Teacher
Chapel Hill, NC
vpitelka at dtccom.net
www.vincepitelka.com 
https://chathamartistsguild.org/ 

-----Original Message-----
From: Clayart <clayart-bounces at lists.clayartworld.com> On Behalf Of William Schran
Sent: Thursday, May 12, 2022 8:56 AM
To: 'Clayart international pottery discussion forum' <clayart at lists.clayartworld.com>
Subject: Re: [Clayart] Death by kiln?

Almost death by kiln: Several years back the now retiring Bill Campbell had a fire in his studio kiln area. Fire department hosed down much of the room. Sitting in the room were Advancer kiln shelves that got soaked. Bill thought he had dried them out but didn't follow the firing procedure set by manufacturer. The first firing with those shelves was a disaster. Shelves blew up and completely blew apart the kiln. Bill told me an employee had just checked the kiln, walked around the corner when the kiln blew apart! So that coulda been death by kiln.
Just this week a potter friend in Australia, Bill Powell had an explosion in a luster firing. He told me it was a normal luster firing he does all the time but in a smaller kiln. It was a small lidded container with a copper red glaze that exploded, shattering every other pot in the kiln and causing substantial damage to the kiln. He can only think the temperature ramp may have been too fast in this smaller kiln.
Years ago, probably about 1972, in undergrad college we were firing a hard brick kiln we had built that was straining to heat up. We tried many things to try to get kiln to heat up better and one night somebody had the idea to position burners right at the burner ports and use bricks to seal off secondary air from entering those ports.There were no safety cut offs on kiln. We would start kiln late at night then return in morning to kiln usually at around bisque temperature. One morning we arrived and looked inside the kiln and there were flames coming up from floor of kiln! The floor was covered in liquid propane!!! We quickly shut it down, opened spy holes, damper, arch bricks in the door and let the liquid gas burn off.
Sealing off secondary air was certainly the wrong thing to do. Could have been a kiln disaster!

William Schranwschran at twc.com703-505-1617

	-----------------------------------------From: "Roxanne Hunnicutt" 
To: clayart at lists.clayartworld.com
Cc: 
Sent: Thursday May 12 2022 7:35:56AM
Subject: [Clayart] Death by kiln?

 >
 > durable outdoor planters

 Oh Vince, I fear to ask, can you substantiate “life-threatening injury”?
 I buy “destroy the kiln! “ But life threatening seems over blown, no?

 Let’s go to there? And deaths by kiln you’ve heard of?

 “Here's another example of how stubborn that impacted water can be.
You
 have no doubt heard about people trying to re-fire a low-porosity vitrified  form after it has been in use. A good example would be a teapot that  someone has been using every day, but then they decide that the glaze would  benefit from refiring. In the firing, such a form can explode from the  impacted moisture, and it can destroy the kiln or even cause  life-threatening injury.”

 roxanne in Oregon where April and May have been like winter. Which is great  because WE WILL BURN IN SUMMER! And need any moisture at all!

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