A heatproof bowl is a bowl that can withstand heat without melting, warping, or burning. They are used for baking, double boiling, and other methods involving heat. Heatproof bowls can be made of glass, stainless steel, ceramic, or silicone. Depending on the material, they can tolerate different levels of heat. For example, stainless steel bowls are heat-proof and can be placed over a saucepan to create a bain-marie or double-boiler. Glass bowls that are heatproof are usually made out of a special kind of glass, such as Pyrex. However, not all bowls made of these materials are heatproof, so its important to check if a bowl is heatproof before exposing it to heat. The surest way to tell if a bowl is heatproof is to check for the heat-safe symbol when purchasing the bowl. Heatproof bowls can usually be placed in an oven, over a boiler, on top of a stove, or in a microwave at high temperatures.