Directly above the burner the gas grill will generally have a rock grate which is designed to hold a layer of lava rock or ceramic briquettes. This has the dual purpose of spreading the heat from the burner uniformly over the cooking surface of the grill and vaporizing food drippings to give food it's barbecue flavoring. Also available are a variety of styles of heat distribution plates which come in a wide variety of materials and designs.

• Lava Rock - The most common and least expensive alternative. The light density of the rock offers quick heating with good distribution. It is very porous which allows grease and char to build up and should be changed yearly or when saturated. When not changed or burnt-off regularly, "rock" catches fire causing extreme flare-ups and out of control cooking situations.
• Pumice Stone - Similar to lava rock, offering the same quality heat distribution, pumice stone has a less porous surface at a slightly higher cost. The less porous surface allows the stone to be baked off more thoroughly for fewer flare-ups.
• Ceramic Briquettes - Baked ceramic briquettes come in a wide variety of shapes and sizes. They are self cleaning by and allowing the heat from the burner flame to bake them clean. Cone or pyramid shapes are designs to allow the grease to roll off without buildup. Replacement is necessary after eventual weakening and crumbling of briquettes. They carry the highest initial cost and vary in cost and quality by the degree of hardness. Through their uniform shape and size they offer superior heat distribution.
• Heat distribution plates - Designed to reduce flare-ups, these plates can be made of aluminized steel, stainless steel, porcelain coated steel, or cast iron. They concentrate the heat more than lava rock or briquettes, therefore requiring lower control settings. The plates have holes or slots that are configured to allow heat to rise evenly through the plate as the plate radiates heat to the cooking surface above. Food drippings are burnt and vaporized as they contact the hot plate.

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