A heat diffuser is a stovetop utensil which ensures that heat is evenly distributed across the bottom of a pan. This is crucial for dishes which need to simmer for a long time on low settings, and it can eliminate the common problem of burned or unevenly cooked food. Many kitchen supply stores sell these utensils, which may also be called flame tamers in some parts of the world.
The material used to make a heat diffuser is typically heavy and solid. Steel may be coated with various substances to make a flat plate, or a company may make a diffuser from porcelain coated cast iron. The end result is a flat disc which will stabilize a pan while also moderating and evening the heat from the stove. In some cases, a heat diffuser may have a handle so that it can be easily moved about on the stove, while other models look like simple dishes.
Both gas and electric stoves can be difficult to modulate, especially on low heat and with older models. In some cases, a stove feels like it only has “hot” and “really hot” settings, and that the stove turns off entirely before a desired temperature is reached. This can be especially frustrating with dishes like rice, which require a delicate simmer, not a robust boil, to cook properly. A heat diffuser reduces the overall heat reaching the pan, while also spreading it out to get rid of hot spots.
Many cooks who use lightweight pans struggle with hot spots. Some metals are more prone to hot spot formation than others, especially as they age and grow thin. If you find that some pots always burn in exactly the same spot, you may find a heat diffuser useful. The devices come in various sizes, from small ones which mesh perfectly with little saucepans to big models which are designed to cover the largest burners on a stove.
Since the heat of the stove is mitigated with a heat diffuser, it is possible to cook with glass and terracotta directly on the stove top while using a heat diffuser. This can be extremely useful for people who do not have ovens, since it is possible to create a sort of dutch oven for roasting on the stove. Make sure not to put glass and terracotta cooking pots onto wet or cold surfaces after the food has been cooked, however, as they can crack.