Thanks for posting your results Heidi. How is glaze fit with NZ6? Min
I've been having some trouble, but I've found many that fit fine.
I don't mix my own glazes yet, and many of the glazes I use are made at Seattle Pottery Supply. All of the glazes I have from there fit fine except my favorite, shadow green, which doesn't fit at all (the glaze cracks and will either chip off the piece or crack the clay if the clay is thin).
Amaco's PC Ancient Jasper doesn't seem to fit it (though I only tested it on one pair of earrings - the glaze cracked off the earrings), Laguna's Caribbean Crackle crackled to the point that it cracked the bowl I used as a tester, and Coyote's Gun Metal Green sometimes fits it. The first two tests were just at the rim over clear, and it seemed to fit fine (though with a smooth crackle effect), and then the third time it got so crackly that it gave the piece a hairline crack. I forgot that and used it again since, and it worked out beautifully (without the clear underneath it, and it didn't crackle), so more testing is needed with that one.
Thanks very much for taking the time to write all this! Sounds like you are getting dunting/shivering from several of the glazes you tried. Did Tacaoma Clayart offer any suggestions as to glaze coe? (You might be able to add some high expansion frit to your shadow green and the other dunting glazes to help fit but then you would probably have to tinker with the alumina and silica also.) It's unusual for commercial glazes to dunt, usually they err on the side of caution and use a higher coe. Is there a chance that the glaze layer was thicker than the clay, especially with the Caribbean Crackle or shadow green?
Yes, I think I'm getting both dunting and shivering. Tacoma Clay Art told me I could try adding a certain frit (I wrote the number down in my studio) to try to increase the coe, but I haven't done it yet. I think I should experiment a little, because shadow green is a wonderfully reliable glaze otherwise and pairs well with so many of my other glazes that I would love to be able to use it on the NZ6, but as of yet I've just been lazy and have busied myself making lots of pure white pieces to showcase the translucence.
The piece that the Caribbean Crackle broke was thin at the bottom where the glaze pooled and got quite thick, so yes, I think it's likely that they were close to the same thickness or the glaze could have even been slightly thicker. The shadow green has never been close to the same thickness as the clay, but always shivers. The time it cracked the clay was on a saucer - the center of the saucer was maybe just under 1/8 of an inch thick (guessing, as it didn't break, only showed multiple crack lines on the unglazed bottom), and where the glaze chipped off I could see it was about 1/32" thick at the most. The glaze was also lifted slightly from the center of the saucer, so it really appeared to me that it wasn't shrinking as much as the clay and was therefore forced to arc as the clay shrunk. I also tried it (shadow green) on a pair of earrings and the glaze came clear off the clay, like the ancient jasper did. It came off almost in one piece (it stuck slightly around the hole).
I can easily avoid the Caribbean Crackle or Ancient Jasper for anything I make with NZ6, but I'd really like to be able to use Shadow Green, so I'll see if I can find it in me to tinker and test.