Mastering the Grill_ The Owner's Manual for Outdoor Cooking - Andrew Schloss [9]
Before combustion takes place at the burners, the fuel must be ignited. Unlike the simple fire starters for charcoal grills (matches and paper, lighter fluid, or an electric heating-coil starter), gas grills typically use an ignition system based on electricity generated by pressure, called piezoelectricity. Some crystalline substances, like quartz, generate an electric polarity under pressure, which sends a high-voltage spark across the face of the crystal. When you push the ignition button or turn the starter knob on your grill, the hammering sound you hear is just that–a small hammer applying pressure to a crystal (usually quartz) so that it generates a spark. You could also light the burners on a gas grill with a match or other flame, but piezoelectric igniter buttons are easier to use when they are working properly.
Once you generate a spark, in order for combustion to take place, both propane and natural gas require a very precise ratio of oxygen to fuel. This ratio (5 to 1) is regulated by the size and shape of the grill’s burners. If the ratio is off, combustion is incomplete and the flame appears more yellow than blue (see the sidebar at left for details on the blue flame). Each burner mixes fuel and oxygen in the proper ratio and spreads it out over the burner’s surface area, where it is emitted as flame through small holes or ports. Better gas grills have separately controlled stainless-steel burners for more precise and variable heat adjustment across the grill’s cooking area. They also have evenly spaced burners that run from one side of the firebox to the other to distribute the heat evenly over the entire cooking area with fewer hot and cold spots.
Most gas grills also include some sort of heat diffuser over the burners to evenly distribute and retain the heat as well as protect the burners from dripping fat and juices. Metal plates, lava rock, and ceramic briquettes are the most common diffusers. Once the heat is diffused, it’s delivered to the food on the grill grates through a combination of radiant heat, conduction, and convection (when the lid is down), as with charcoal grills.
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C. Grill Cleaning, Maintenance, and Repair
Most grills fail or need repair because they are rarely cleaned. But you don’t need to scrub your grill until it gleams like a sports car. After several uses, a grill naturally develops a light patina on the grill grates and firebox that gives it character and doesn’t negatively affect performance.
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LEAK TESTING ON A GAS GRILL
There are two ways of detecting a gas leak. Although propane and natural gas are odorless, ethyl mercaptan is added to these fuels to give them a detectable odor. Mercaptan reeks of rotten eggs. If you smell this persistent odor, do a leak check to locate the source of the leak. Mix a 1-to-1 ratio of dish soap and water. Turn on the fuel supply at the fuel source only (the propane tank or the natural gas line), but don’t open the temperature control knobs on the grill’s control panel. Brush the soapy water over the hose(s) and connections between the fuel supply, fuel valve, and temperature control knobs. Anywhere that bubbles appear indicates a gas leak. Inspect the hose(s) and connections for cracks or worn areas (grease sometimes attracts rodents, who may chew through the hoses). Next, brush the soapy water onto the welds around the propane tank, its supply valve, and the bottom ring of the tank and check for bubbles. Tighten all connections and immediately replace the hoses, valves, or fuel tank as necessary. The same bubble test should be performed on newly installed hoses, valves, and fuel tanks to confirm a tight seal with no gas leaks.
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Of course, if you have a ¼-inch-thick layer of soot and carbonized food on the grill grates, firebox, or lid, you may want to consider