I would contact a specialty tile/flooring store and ask what kind of adhesive they recomend to start. I would think that the ceramics would need to be porceline in finished state also. Hope that helps!

IMO I can't see any other way to adhere the tiles than w/a good tile mortar, and of course I'll repeat my favorite - Mapei Ultra Flex II, found at Lowes. I agree w/CALAM that the tiles should be porcelain.

Porcelain tile would be good. However, what do you all think about vitreous glass tile? Wouldn't it be appropriate also? I think it would, but I'm not an expert, so I would like to hear what you think.

Yep - those w/work too, IMO.

It's hard to tell from the pictures what the base that the tiles are on is made of. If it is something that would expand/contract as the pit heats up and cools down (like metal, which is what my fire pit is made of) that could lead to problems with the mosaic cracking or pieces popping off if they were attached directly on the surface. If the pit is made of something that expands you could still make a mosaic on something like a thin piece of cement backer board and attach that to the pit, I think (not an expert here!!).

shrill, I'm thinking the same thing, metal is going to change pretty drastic just in the sun.. I don't think I would adhere a mosaic to metal. I agree that I would make a cement board base and screw it to the pit rim before mosaicing. I also would trust silicone over anything else for the heat resistance

According to the label on the silicone I use, It is resistant to 350 degrees farenheit. Some epoxies go much higher, you have to check the labels. there are pple on flickr who have mosaicked outdoor pizza ovens. they used mortar-but the ovens are so well insulated there is snow on the outside of it while the oven is fired up and running. sorry for the spelling nd grammar-in a hurry!