Yes, tumblers can be coated with Glaze Coat. If you drink from a straw or lid when using the tumbler then Glaze Coat can be applied up to the metal lip of the cup. If you plan to drink directly from the tumbler, ensure your mouth will not come into contact with the Glaze Coat. Tumblers are not dishwasher safe once coated with Glaze Coat. Hand wash only.
Glaze Coat is not classified as “Food Grade” or “Food Safe” for direct food serving or storage by the FDA. Properly cured Glaze Coat surfaces are safe to serve and store food on so long as the food is contained in or on a plate/container intended for direct food use. Heating, serving, and storage of food directly on a Glaze Coat surface is not recommended.