Are you using unglazed quarry tiles? Way back when I really cooked, we used these in regular oven to bake bread. I'm pretty sure Julia Child was one who recommended them for good crusts...so I expect her advice was widely followed. Don't ever remember any concerns being raised. Not sure if this is applicable to use of these tiles in microwave...just thought it might be somewhat reassuring.

I've seen in more recent years something called pizza/bread stones for sale in upscale chef catalogs...but again, they were for use in regular ovens. You would have to ask about safey in microwave..They might be made of some stone-like substance not safe in microwave.

I've used two of the Pyrex glass pieplates to dry a few things. Just some I had on hand and they fit together...seemed a good solution over buying one of the microwave drying kits. I just place my blotter material in one, then flowers, then more blotting material, then another pieplate, and a 1/2 cup water in a pyrex measuring cup on top. (The water was suggested in my microwave oven instructions to "prevent over-dying"). Do you use water?

I've only dried a few things using microwave...mostly I press-dry. And mostly foliage, not flowers. So take all this with a 'grain of salt'...okay? Hope someone else chimes in with more experience...josh

Pyrex would be very safe. Every tile is different. It would depend on the clay used and how it was cured or baked. Soil can have any content.

I was really excited when I bought a steam cleaner. I figured I wouldnt have to use soap, and I could kill germs on baseboards, bathroom floor, counters etc. Boy, when I applied hot steam on various surfaces the fumes almost killed me. Leftover cleanser traces, the dirt itself, modern composite surfaces. The plastic toilet seat gave up fumes like you can't believe. Steamer was returned to store.

Now I am very careful about what I heat up

I don't know for sure, but I've been looking longingly at the microwave press set from Lee Valley and they look like they're regular terra cotta! What a great idea to just make your own and probably save $$$ to boot! I hope I don't sound ignorant, but I'm sure the plastic tupperware things and instant meal trays release much worse... stuff, fumes or whatever, than anything as natural as clay! Great idea- I might have to head to the Despot and ogle the tile aisle!

Here is a link that might be useful: Lee Valley Microwave Flower Presses