Wednesday, September 22, 2010
Test tiles unloaded first thing this morning
Yesterdays firing of the little Olympic gas kiln was certainly filled with some drama. At the lowest setting it kept shutting off, so I eventually got the pressure up enough to keep it going for a while. I wanted a fast firing because I knew I'd had to finish early so I could unload this morning because of the thunder storms arriving around 1 o'clock (current weather report). Then the fluke pyrometer stopped working; but fortunately that happened once the cones starting moving. I had a back up thermocouple and attached it and it still wouldn't register above 90 something degrees F. I got the manual out and nothing in there seemed to address the problem, so I'll have to play with that and test it in the cone 10 small, electric test kiln in the next few of days.
The kiln is currently on a cart and was fired, surrounded with metal roofing pieces that I cut and used to keep the wind out, but the problem is that the cart length is longer than the kiln, making it difficult to totally protect the burner system, so around C 9, the slightest breeze kicked it off. Fortunately I was near the kiln when it occurred. Working quickly I got the the kiln re-lit and continued firing and salting. The 7 gallon tank seemed to have enough gas left; but I opened the gas on the other 5 gallon tank that was manifolded with the other one, just in case that was the problem. I had to re-light the kiln 3 times at top temperature; but managed to get all soda solution in before it shut down again around 3 o'clock. At that point I just called it a day. I figured I'd have the information I needed. Since this kiln is so small (around 3.95 cu ft), I only 1 1/4 lbs of salting material - a combination of equal parts soda ash and sodium bicarb and a 1/4 lb salt combination. I wasn't aiming for heavy salting just enough to liven up the slips.
This morning I unloaded around 7am. The top shelf had a flat cone 10, 11 starting. Slightly above the middle was cone 10 starting, and unfortunately I did not have a cone pack at the bottom but all the slips on the bottom shelf are very dry, so I think it might have reached cone 8 and certainly not any more. I'll re-fire those tiles in my tiny cone 10 electric kiln in the next few days.
The shelves were staggered well, lots of space above the tiles, so there was nothing to keep the heat from distributing fairly evenly other than the fast firing. Having fired an old 7 cu ft California kiln, and hearing about other updrafts, uneven temperatures seems to be a problem with many updrafts. If anyone is firing this little Olympic kiln and getting even temperatures I'd love your input!
This morning I have to order a part for one of my tiny C10 electric test kilns and this afternoon I'll go over the tiles, make followup notes ,and set aside the ones for re-firing. The re-fires should bring up more color on some of the colored slips. A couple will need to have new tiles made and fired in my regular soda kiln in November.