Metal surfaces such as tumblers, flasks, knives, pewter, stainless steel, and brass can etch in seconds. Sandcarving has become a popular method for metal surfaces because it is a quick process and provides the option to paint-fill. Sandcarving will only remove the surface; depth cannot be achieved in metal.
We recommend using a self-stick film for metal surfaces in 3mil or 4mil with a quick etch. Self-stick film removes easily after sandcarving — this benefit provides a perfect painting stencil. For coated metal surfaces, such as Yeti and Ozark, use a 5mil photoresist film, which provides enough sand resistance to remove the coating. It is essential to paint in light coats for metal surfaces since there is no depth.
—Liz Haas, Rayzist