Friday, June 27, 2008

slow reporting in

As of Wednesday I've known that the kiln did fire successfully after Tony changed the breaker. However, I feel only partly secure that the failures are behind me. The test fire I ran after Tony worked on the kiln the first time was successful but the subsequent firings were not. So until I fire the kiln another time or two I won't be totally certain that all is well.

As to the pots that were in the successful firing...they were an awful mess! They had been in 3 or 4 unsuccessful firings. So that may have played a part in their destruction. But there may have been another more significant factor. I was so tired of loading and unloading the kiln that I decided to 'test' fire with all the pots loaded AND I decided not to program the firing as I ALWAYS do. Instead, i set it to automatically fire to cone 6 at a medium rate. In my book, it overfired. However, cone 6 is set to fire to 2236 F in this mode. I never fire higher than 2190 F--usually to 2185 F. I had 3 cone packs containing cones 5-6-7. All of the cones were down. Cone 7 was down touching cone 6--it still had a slight arch but it was riding on the back of cone 6.

So what was the effect? I had several shallow bowls in the firing. The glaze popped off the upper area of the outside and fell in pools on the (new) shelves. The glaze did not run down the side of the pots--it blew off the pot and landed a few inches away from the foot of the bowls. On the inside of the bowls it did look like it flowed down the inside of the bowls. There were probably 8 or 10 pieces that were thus affected.

On the other hand, I had about 18 test tiles in this firing. Only one or two looked like they were overfired--like they had been burned. The others look good--exciting in fact. I just hope it does not mean that these glazes have to be fired this high to be successful. This was the high point of the firing. I had mixed up 5 different base glazes and had made 3 or 4 variations of each. It is the first time I have done this and it was very interesting to see the similarities and the differences in the variations. I have not made photos of the glaze tests. I am discouraged by how hard it is to get good color reproduction from my photos.


chaetoons said...

Mornin' Gay
Sorry to hear about the glaze firing going awry. Glad to hear the test tiles gave some interesting clues.
I absolutely know how discouraging it is to open the kiln find find less-than-positive results !!!
As YOU are always telling me - hang in there. It'll all come together wondrously.

Ron said...

Well it does look like you fired to cone 7. I have no clue why that glaze would pop off like that. I'll check my Hamer book and see if it gives any explanation. I hate that you're still having bad times with the kiln, it's a real downer after putting all that work into the pots and glazes.
On a positive note, from looking at those cone packs it seems your kiln is firing quite evenly from top to bottom.
Keep up posted.