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Isn't kitty litter pretty much all bentonite? Look at the product label in some cheap brand and see if that wouldn't work for you.

pottery place will likely have catalogues or just google bentonite. i think the archives at clay times magazine would help with the exact cleansing protocol. also monona rossul (sp?) has discussed this. rosanna ps if it is galvanised, tell your metal supplier that he/she is a dumbass. rosanna

Did a test fire with scrap and there was absolutely no scum or even a trace of devit on the piece! Yeah! It did seem to be a little darker than the other pieces that I have made with the same color...strange. I used a transparent medium/dark blue. Don't have any reactives to try. Perhaps I should throw some clear in to try? Do you think I still need to clean it out with the clay?

Don't have a torch to see if the metal is, perhaps, galvanized. Don't think I'll put any more in the kiln anyway!

that is good. i would not bother with thw bentonite unless you get problems with reactives in the future. the burner on a gass grill would work or even a small bonfire or pile of charcoal would be enough heat to test the metal. rosanna

Any chance something crawled under your kiln shelf before you started firing and that's ash?

Tony

Nope, nothing under the shelf. I had taken it out to do the setup. I did another test with clear scrap, and all seems okay now. Whew! Thanks again to ALL for you help! Nothing else in my kiln unless I know exactly what it is - although I thought I knew what this was

Think I'll pre-fire EVERYTHING now. Never really needed to pre-fired before, so when I vent the kiln to prevent something like this from happening by pre-firing, at what temp do I vent the kiln?

Usually, by the time you get to 1000ºF, organics are burned up. Venting allows more oxygen to re-enter the atmosphere, which would remove a reducing atmosphere.

I am still concerned about your phenomenon. I have never seen anything like this before. I'd like to know what your metal really is, considering this seems to be the grayest area of difference from the norm.

So do I vent at 1000,or lower? How long do I vent for?

I'm sending a piece of metal to my son- a phd candidate chemist -to test. That should finally answer some questions.

Vent UNTIL 1000 . . .

smallbitz wrote:I'm sending a piece of metal to my son- a phd candidate chemist -to test. That should finally answer some questions.

Your son the chemist may well have the best clue as to what would cause crystals to precipitate all over your kiln interior. It is not a big surprise that crystals sitting on the glass surface at high temperature would promote devit (devit is also crystalline).

I'll post when I get results from him. Thanks again for everyone's help!