Friday, November 28, 2008

Kiln week from hell!

Finally got my soda kiln fired after several glitches with bisque,, liner glaze problems and just plain clumsiness and equipment failures! Getting back to work after a year off due to a non working hip and then recovery from hip replacement surgery, has been a bit challenging, tiring and awkward at times. First there was hundreds of pounds of hard clay and reclaim clay to deal with as well as major studio cleanup to do before getting started throwing.
Throwing went OK other than dealing with clay I over softened; but it didn't take long to get those muscles back. Then there was the joy of getting all the slips and glazes remixed and sieved - another daunting task.
Loading the second of the two bisque kilns went fine, and then unloading the second bisque turned out to be a crashing experience, as one of the tall posts on one of the half shelves decided to topple as I was walking away from the kiln to put down another shelf. That little crash resulted in several cracked pots. No problem. I had extras. Then several bowls with a cream liner, which looked fine on application on a raw, dry pot (evenly watered it down quite a bit),cracked horribly in the Cone 03 bisque and was too fused to be removed -more lost pots.Then, while wadding and loading the soda kiln , a 9" half brick post toppled onto 3 small pots sitting on the kiln floor, waiting to be loaded - more broken pots! Suddenly my full kiln load was looking pretty sparse, so I went around the studio looking for a couple of likely candidates for re-firing.
There was a nice, large bowl among the likely candidates and that filled half a shelf, and I found a couple of old plates to glaze, so things were looking pretty good. Kiln finally got loaded, bricked up, with pilot burner on overnight. Next morning it was over 300 degrees and I proceeded with the firing, going nice and slow, as I always do. Around 550 I heard the explosion -fortunate that I was there to hear it!.
I turned off the kiln and had to wait the following morning to deal with it. Got up at 4am, walked the dogs, unbricked the kiln door to discover that it was the big refire bowl that was the culprit. The kiln gods weren't too cruel, as it was on one of the upper, front shelves, so I didn't have to unbrick the whole door - just the first 8 -10 courses or so. I was able to reach down to the floor to pick up some large chunks and was able to reacht he likely places to remove chards that had settled inside of some pots. There were some shelves that had to be removed, and I had to re-apply some loose alumina hydrate and reload those shelves and brick her up again. By 7am I was back firing.
Great, I thought;but the kiln demons weren't done with me! Twice during the lower temperatures, the burners kicked off; but Iwas so tired that I had affixed myself to my camp chair in the kiln room and was there both times to re-start the burners immediately. Other than bathroom visits and one fifteen minute break to quickly gobble up the Kentucky Fried chicken dinner that Jim had brought home, I sat near the kiln. I wasn't taking any chances with how my kiln luck was going!
Well, at 2000 degrees, the kiln kicked off again, so I jet propelled myself out of my camp chair and quickly depressed the button on the safety valve. 10 minutes later, after multiple tries, those burners refused to go back on without me holding the button down. By now the pen hanging on my sweat shirt was burning me and my metal watch was burning my left wrist, and the water was dripping off my forehead at an alarming rate. So Iquickly released the numb finger on the button, closed up the ports (burned several fingers doing that), and damper ran into the house and screamed to Jim to call Shane. I quickly ran back to the kiln room, started the burners again, and they were kicking back (I forget thatI had the damper in and didn't remember until Shane got there!) But I at least got the pilot on and in about 10 minutes Shane showed up and determined what I had already figured out, that the basal valve was probably shot. He said it could also be the thermocouple in the pilot burner, so using his amazing strength and two large wrenches, he managed to take the thing apart and jerry rig his extra large C clamp to keep the pipe connections closed so Icould finish the firing.
By the time we got the kiln turned back on it had dropped to 1700F.
Another thing - the kiln had been firing hot at the top in past firings so I had Shane add to the chimney so that it would be about 3' higher the the roof peak. He also adjusted the bag wall earlier when he did some other work on the kiln and burners. Unfortunately,we probably should have only made one adjustment because the higher chimney did what I thought it would do - make the bottom hotter! Theproblem is that we also opened the bag wall a lot at the bottom, so it got a lot hotter! I wound up with cone 12 at the bottom left and on the opposite bottom at the read, with cone 10 barely starting in some places on top, and various levels of cone 10 and 11 in some other places.
Since it was already past my ideal peak temperature, I decided to accelerate the salting (I had already done some of the Nichols whiting/sodium bicarb mix and some wet soda ash applied to scrap wood pieces, and one salt burrito) and wound up throwing in 2 more salt burritos, a couple more angle iron doses of the Gail Nichols mix, and one round of spraying soda in about 8-10 ports. The draw tiles looked like I got some surface shine, so I'm hoping I put enough material to do the job. I have no idea how much salting material actually went into the kiln! In panic mode, and time being of the essence, I wasn't going to be fussy about weighing anything. At 2am after a much needed shower, washing and blow drying my hair (I smelled like a fireman after a day fighting fires!), I finally crawled into bed, convinced I should take up book binding or or some other less strenuous, less dangerous activity at my age!
The kiln has been cooling for a couple of days and is now about 220 degrees, so some time late tonight or more likely, tomorrow morning , I'll be able to start unbricking the rest of the door. I've peeked in and from what little I can see, things don'tlook too bad. The pots are quite dark from the 3 salt burritos. One plate has a couple of pieces of debris in it and that's one of the pieces I check earlier. It was clear then, so it's a major puzzlement where they came from.
Well that's the end of my woeful tale, if you've had enough stamina to read this novelette!

Till next time,
June
http://www.shambhalapottery.com
http://shambhalapottery.blogspot.com
http://groups.yahoo.com/group/sodasaltfiring/

2 comments:

John Britt said...

Quilting anyone!?

John

John Britt said...

June,

Have you recovered?

John