Although I'd love to get into the nitty gritty of how powder coating works, that really is enough info for an entire other instructable! For now, if you are completely new to the powder coating process, I'd suggest familiarizing yourself with it from the wikipedia page
Powder coating is awesome for a lot of reasons, but the trickiest part is trying to figure out how you are going to make something conduct enough electricity to deposit a thin layer of polymer/dye mix on it. For these particular tiles, here's how I solved that problem:
First, I set up a steel oven grate and attached my powder coating grounding cable directly to it. On top of the oven grate, I added a piece of waxed paper to keep powder coat from sticking to the grate itself. Finally on top of the wax paper, I placed my tiles. For those familiar with the process, I did not do any pre-treatment of the tile whatsoever - no cleaning, no degassing. I then loaded by powder gun with a copper vein powder from Columbia Coatings
, and got to spraying using a 10,000V bias. The cost of 1 lb. of the powder? about $15. The amount I used for this project? Maybe 1/10th of a pound. This is the other reason why powder coat rocks - there is so little material usage, and its so cheap!
In the end, I had a beautiful even coating on top of my tiles!
I then carefully
moved the tiles from the oven grate and wax paper, and baked them in a convection toaster oven at 400F for ~15 minutes (manufacturers recommended settings). Be careful not to knock any powder coat off during the moving process - at this point there isn't any force keeping the powder stuck to the surface other than some residual electrical charge!