I recieved new kiln shelves for the university today. We ordered from Larkin Refractories, a place where I've gotten the majority of my kiln supplies since I left school. I ordered a bunch of their 12x24 "Fines Bonded" silicon carbide shelves many years ago(chinese imports)and I have been more than thrilled with them. 30+ salt firings, 15 wood firings, never flipped, never cracked, flat as when I bought them. In salt firings the salt just beads up(or foams up) on the surface and is easily scraped with a rub brick, never once had to use a grinder on these from the salt kiln. The salt and ash combo from the wood kiln can require the use of a grinder but it never takes away any of the shelf, they come out looking brand new. They are 1/2" thick and have relief cuts that are supposed to keep them from warping & cracking, in my experience it works. So at $45 each I thought they'd be fantastic for the school.
The new shelves come with a kiln wash already applied. It's powdery so I'll just scrub it off and apply my own...I don't like not knowing exactly what's on them(can someone say"control freak"?)
I've heard some rumors on clayart over the last couple years that these kiln shelves often show up slightly warped, I thought this may be a fluke since mine were fantastic. I don't know if Larkin changed the supplier or if the supplier changed their quality control but many of ours are warped. You can see in the photo below the gaps between the shelves as they rest up against eachother.
About 1/3 of these are warped enough to notice, but still much flatter than the shelves we use now. If they're anything like the shelves I use they shouldn't go any further out of shape. If I were a production potter making lots of flatware(plates) I probably wouldn't buy these shelves. On the other hand for student work, small work, or kilns where the pieces are wadded I think these are a great buy. Hopefully they're just as study as mine, they'll go into rotation real soon so I'll keep you posted.