Cons : This is the cheapest grade vermiculite I've ever seen, crumbles, dusty, guaranteed to wreck whatever you're working on . I bought it to confine casting pieces and found it a total waste. No matter how careful you are it will wind up in your piece.
Pros : I love working with the vermiculite boards. They are great for "building" glass pieces on in layers and not having to carry something to the kiln that is not steady. I find them incredibly handy. They are also great for making tons of dots. Line them with thin fire and use your scraps to make dots. Fire once the board is full. It is low profile, so I can keep it in a drawer and keep working with it until full.
Cons : I stilted a board ONCE and it warped at 1500. I won't be able to use it again. I was very surprised that it bowed in the middle. Two pieces were ruined because of the warping. I still love these boards and will just never stilt mine again.
Other Thoughts : You can cut these boards into shapes and sizes, which is very handy. The vermiculite does leave some board powder residue behind on the kiln shelf after firing.
Pros : I LOVE THESE!!! I cut the 12" tiles into 4 piece to use in my kiln. They are perfect as I can still get my hands in when setting the tile down in the kiln. This allows me to set the tile in while keeping it perfectly flat. Nothing falls off, and I don't have to re-adjust anything before I close the lid! I have used them again and again and again. I have used thin-fire sheets on them for the most part, but find that after several firings there is enough of the powder left from the sheets that I can actually do several firings without anything. You go get a rougher back on the glass, but I don't care as most of my pieces I bead around so the back is covered any way. I have had the glass grab the tiles from time to time, so I would still recommend the thin fire. Using kiln shelves with kiln wash, etc. is just not my thing. I don't like having to re-coat the tiles again, and again. Also, I take my glass out when it is still pretty hot so these are great!
Cons : They are kind of messy...but that is the only negative I have. Of course, you can't use kiln wash with them as they can't get wet. But I prefer thin fire sheets any way.
Other Thoughts : Wish they made these for high fire ceramics...say to 2300 degrees or at least Cone 6.