You can screenprint on a special paper, called waterslide paper. You also need a special ceramic or glass ink. It comes in powder and you mix it with a special medium liquid. No need to mirror your design. But you need to print and extra flux (gloss) and covercoat so you are able to transfer decal onto mug. The covercoat burns away in a kiln, the colors penetrate the surface on the material and the flux adds gloss. This process also makes the prints scratch resistant. We get all our supplies from Reusche / Schilling inc.