Hi all, Coming back to this forum after it helped me solve a looong battle with S-cracks several years ago! Here today with another technical problem... I've been making coasters in large quantities and struggling with warping that makes the coaster unusable/unsellable. Here's my process -- I think I have an idea where my issues could be, but wondering if anyone else has tips or notices anything that might have to do with the struggle to keep the coasters flat.
1. Roll out slab using slab roller
2. Compress with metal rib
3. Cut circular coasters with cookie cutter
4. Here's where the problem maybe is -- usually the coaster sticks inside the cookie cutter and I gently press it free onto a piece of drywall, trying really hard to not do anything too drastic. But definitely occasionally picking up a wet slab or coaster. Maybe I should be waiting for the slab to be leather hard, then cutting the coasters, and peeling away excess as opposed to ever picking up the coaster before it is leather hard and thereby preventing the slab from "remembering" later on that once for 2 seconds I picked it up and it bent a little and now it wants to bend again? lol.
5. Stack drywall layers atop coasters, weigh them down with something, let them dry slowly over days
6. Once leather hard/nearing bone dry I do a little trim to neaten up the sides -- usually scrape over the coaster with a metal rib to flatten out, and use a damp sponge to smooth the sides at the end. Add underglaze decoration once bone dry. All coasters appear flat at this point
7. Slow bisque to Cone 04 - coasters still appear flat at this point, with maybe 1 casualty
8. Glaze medium speed to Cone 5 with hold - here is where, of maybe 25 coasters, 5-6 will be totally unusable (often a side curls up almost a quarter inch) and most of the rest are passable but just don't sit as flat as I'd like.
Am I being unreasonable to want flat-flat coasters? Haven't seen a lot of potters selling coasters and wondering if this is why...
Here's a picture to help show what's going on:
https://drive.google.com/file/d/1l3k1dYW3qxpCjqS3AcCmtHsT3jskLNbz/view?usp=sharing
Thank you so much for any tips/advice!!!
