Tracey, thanks! If I ever find the other pieces, mine and my friend's, I'll post them, too. Your projects sound like fun, too!

SRS, I think we might be talking about two different kinds of tiling. Painting them, to me, means clay tiles which are then fired and yes, the colours are fixed permanently.

What I learned to do and still need to learn a LOT more about is more properly called "enamelling" in which glass is fused to metal using a kiln. We used copper tiles, cleaned them in "pickle" (an acid solution), then used a spray on glue/fixer before applying the sandlike glass colours. Each colour has to be done in a separate firing, but each one only takes about 1-3 minutes, sometimes more depending on size, etc. The beauty of it is kind of like watercolours. If you don't like the way it turned out, you can fiddle with adding more glass, more colour, etc., then fire it again.(Each time you heat it in the kiln, you can change it by how you place the powdered glass colours.)

One may also use forms of glass, for instance, the green tendrils of *seaweed* on the blue tile were just small rods of green glass which I cut to length and placed on the tile.
This might explain it better and has a gallery of some nice work.

As for the bumps, I do have one piece a friend did in which she used millefiori beads to create contour.

Good luck at keeping the kids outta the castoff bits!:-)

kat