large platters

[mark knott]

i wanted to ask all on this who make large platters how they are wadding their platters? I have been making and firing large platters for a long time, but recently it seems the platters are shrinking off the wadding. It's as though the wadding is not moving with the platter. The result is serious warping, both porcelain and stoneware. Has anyone ever put down a thin layer of alumina to help the wadding slid/shrink with the platter? what size wads are others using. How many wads?

I am firing on some nitrate bonded silicon carbide shelves from a 18x18 that cover the gap between my regular shelves. These shelves are extremely flat and resist soda well. The platter sizes are from 22'' to 26''. it seems strange to be encountering this issue now. Any thoughts would be great or any other methods would really help. Thanks, Mark Knott

[Colleen Riley]

Hi Mark
Here is something we've been playing around with, and it's worked great. This idea has been floating around (someone mentioned it at the NCECA gathering, and possibly Jane Hamlyn, and a couple of French potters)...
Mix kiln wash to thickish glaze consistency, stir it up so it has NO lumps, then add a little wallpaper sizing so it sets up (maybe 1 Tablespoon to about 2000 g of wash). Spread it on the kiln shelves like mortar, using a notched tile setting trowel to apply. You'll need to experiment a little to figure out how deep to make the grooves, how wet to mix, how thick to apply, etc. It takes a while to set up and will crack up a bit as it dries. But so far we love using it for flat pieces. No need for wadding, no warping, easy loading and you'll get cool striped flashing on the bottom! We've been able to reuse the grooved shelves if we're careful handling them. We're using this on our regular silicon carbide shelves.
If you give this a try, tell me what you think. Has anyone else tried this?
Colleen

[mark knott]

Colleen, Thanks for the idea. I'll give it a try next firing. I wonder if you could not do the same idea with wadding. May be I will try both and report back. Mark Knott

[Kyle Carpenter]

Hey mark,
i've put straight alumina and water on the platter foot and had good success. This washes off very easily post firing. I use wadding mostly. I put a wad about every two inches and somewhat large. Also, i've heard of mixing wax and alumina. I hope all is well in GA.