Tuesday, December 27, 2011

Cone 6 soda test firing cooling

The firing went well and I was home before 7pm. Love it! I think we may have gotten a bit hotter than our goal. Cone 6 in the only cone pack that was visible didn't seem to be moving although the pyrometer showed it should be. So I opened the burner shutter more and adjusted the damper for light reduction and we went off for a few minutes and when we came back cone 7 was at 3 o'clock, even though cone 6 hadn't shown any sign of movement a couple of minutes before! With soda you never know if that's a true reading; but I had the cones inside a little open hut of sorts to protect it somewhat from the soda in an attempt to get a truer reading. The tiles should tell the story.

The last draw ring showed good gloss from the new soda mixture (which Dan Hill uses for cone 6) which was 4 parts sodium bicarb, 2 parts soda ash and 1 part borax. This soda test kiln is small - maybe 4 cubic feet of setting space, and I didn't even finish the 1 gallon of solution which had 1 1/2 lbs of the soda mixture. In fact, I may have gotten a bit more in there than ideal. We'll see.

John thinks we may be able to open it this morning. I'd be thrilled to have one workable flashing slip from all those tiles! If not, we should have enough information to explore it further.

The high grolleg flashing slips tend to be dryer than some others unless fluxed a lot or have some clay substitutions. Ronan Kyle Peterson said that his experience has shown that replacing the grolleg with EPK was an improvement. So I can try that in future tests if needed.

In our first soda firing, using the Gail Nichols method, straight cone 10 flashing slips were all dry or very dry; but there were some that had more possibilities - Randy's, one of my Avery clones, and two others. I didn't put those originals in this firing with the newer soda mixture; but I did have several variations of those in the firing. Looking back, it might have been a good idea to put at least one tile of those 4 original ones in the firing with the new soda mix as a good comparison.

Another very good suggestion from Ronan was to sub Redart for some of the more refractory clays. Randy's uses Newman red which is classified as a fire clay, so that is another possible, future test.

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