Lava rocks retain and reflect heat from a propane grill for cooking food. The rocks are traditionally used with a gas grill because of their ability to heat quickly and radiate for even grilling. With regular use, lava rocks should last for about two years before replacements are needed because of the buildup of grease, which can affect flavor, as well as the natural deterioration of the rocks from frequent heating and cooling.
Raise the lid on the grill, remove the cooking grate and pour new lava rocks onto the grate over the propane burners.
Arrange the lava rocks in a single layer on the grate over the burner with the edges touching each other, then replace the cooking grate. The rocks should not be stacked on top of each other.
Turn on the gas and ignite the grill, then close the lid and let the grill preheat for 10 minutes.
Arrange food on the cooking grate and grill according to the recommended time listed on the recipe.
Remove the cooked food, then turn the grill burners up to high to burn off grease and spilled food on the lava rocks. Leave the heat on for 10 minutes; this cleans the rocks for the next grilling session.
Remove the cooking grate and turn the lava rocks upside down (when the grill has cooled) after four to five grilling sessions. This helps clean the rocks and wear them evenly for longer use.
Replace the old lava rocks with a fresh bag when the rocks begin to crumble or produce a persistent grease odor that cannot be removed by heating the grill for 10 minutes.