A strong, durable printing plate used in offset lithography. Trimetal plates, as their name indicates, utilize a metal base (either stainless steel or aluminum) which is plated with copper. The copper layer is then plated with a thin layer of chromium. During platemaking, the chromium is etched away from the image areas, baring the copper below. The chromium remains to form the non-image areas of the plate. Trimetal plates (as well as bimetal plates) are expensive, but are particularly useful for long print runs.