A quick ceramics primer:
The temperatures called for can range from 700 to 1200 degrees for low-fire techniques like the iron transfer decals to 2500 degree (farenheit) or so for high fire porcelain with cobalt decorations. That famous blue seen in both Chinese and Delft pottery is cobalt. Most photo processes are done in what is known as overglazing, a method of adding colorful topcoats to an already fired piece that is then fired again at a much reduced temperature to fuse it to the glaze. Gold chloride is used like this to produce the gold rims on fine china services. The overglazes are much like enamels baked on to the surface of the glaze. Underglazing, a much more permanent process, has the decoration applied to the once-fired but unglazed bisque-ware, which is then covered by a clear or translucent glaze and fired to a higher temperature. Underglazes tend to be monochromatic or muted colors and are dishwasher-safe. Many colors burn off at high temperature. Reducing the oxygen available during the firing process will result in changes to many glazes and can result in colors that cannot be produced any other way; certain reds are reduction colors because most red pigments burn off at relatively low temps.