alord

Well, to make things more interesting, I found this when I removed a large chunk from the broken creamer. This is looking at the cross-section of the wall of the piece. I'm not sure what would cause this, maybe leftover organics? I couldn't find more examples of this in the other broken pieces of the creamer.

Callie, Thank you for your response. I'll read through the Digitalfire article and see what I can glean from it. I'm basically out of this batch of clay, so I'm not really that inclined to do much to it. These results were just a bit unusual for me and I'd like to get an idea of what could cause this. I have thought of incorporating the clay into a glaze or slip and I'm thinking for trouble's sake I may move in that direction. I was also testing a glaze when I fired these pieces, so I used the "Fast Glaze" setting on the kiln controller; I presume the "Slow Bisque" firing setting may have yielded better results. The jug is not crumbly or soft in any way. It feels like normal bisqueware. Once it's been bisqued, would a glaze firing also need to be slow? As far as adding a feldspar, the local ceramics shop has a couple (Custer, Minspar, Nepheline Syenite), would it matter much which was added?

Howdy, I recently processed some wild clay and have been having issues with it. Originally, I bisque fired it to cone 02 and it melted into the blobs shown in the first image. I then tested a cone 05 firing and the test tile survived, but had a bunch of small cracks. I tried another bisque firing with more test tiles and a thrown piece and they suffered the same fate. Does anyone have any idea what about the clay body could cause this? Is there anything I could add or test for that would help? The clay threw well enough, though I did notice that the greenware dried very slowly and when bone dry was remarkably strong (I literally threw one of the test tiles at the pavement and it didn't break). The clay came from a rocky region of central/western Texas. Any input would be greatly appreciated. God bless.