Mastering the Grill_ The Owner's Manual for Outdoor Cooking - Andrew Schloss [8]
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Charcoal
Natural lump charcoal and briquettes are both forms of burned wood that has already expended more than half its potential energy. That’s why charcoal fires don’t burn as hot as wood fires. It’s also why many people swear by grilling over wood rather than charcoal or gas for the most intense heat and the best browning (and most complex flavor) in grilled food. However, charring wood makes it easier to ignite so that its heat can be more readily harnessed for cooking. Not everyone can start a wood fire every time they want to grill.
When wood is preburned to make charcoal, most of the wood’s volatile organic compounds are burned off in the form of smoke. What’s left behind is carbon, which produces the heat in glowing coals, and ash, which is made up of minerals left behind after the carbon has burned off. This explains why charcoal fires (and wood fires that have burned down to coals) don’t emit much visible smoke.
Charcoal ignites at roughly 600°F, and matches, paper, or lighter fluid all get the job done. Once charcoal has ignited, its carbon combines with available oxygen to produce carbon dioxide, which results in heat. The ratio of charcoal to oxygen determines how hot the fire will get. The air vents on the firebox and lid of a charcoal kettle grill allow you to increase or decrease the flow of oxygen to speed up or slow down the combustion rate and, consequently, raise or lower the grill’s heat. An elevated fire grate also improves airflow, allowing for easier temperature adjustment. With no lid, as on a hibachi, a charcoal grill also receives oxygen from above, but it’s more difficult to control that oxygen flow. A gust of wind can fan the flames and instantly raise or lower the grill’s temperature.
Steel is the most common construction material for charcoal grills such as kettle grills and hibachis. Steel is a good conductor of heat, so it heats up and cools down relatively quickly. But it doesn’t retain heat very well, and so metal grills generally require more fuel because the heat is lost more easily through the grill’s firebox. Ceramic charcoal grills, on the other hand, don’t conduct heat as quickly but are far superior at retaining heat. Ceramic grills run more efficiently, requiring less fuel because heat is retained in the grill’s firebox.
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BENEFITS OF A CLEAN BLUE FLAME
When burned with an optimal mix of fuel and oxygen, both propane and natural gas emit a clear blue flame with no smoke. A clear blue flame indicates that only harmless water vapor and carbon dioxide (CO2) are formed during burning. A yellow flame indicates insufficient oxygen for complete combustion of the fuel to take place. A small amount of yellow at the tip of a blue flame isn’t hazardous, but a complete yellow flame will emit a bit more carbon monoxide (CO), a colorless, odorless toxic gas. You should be concerned only if the yellow-flaming grill is in a very confined area with poor ventilation. But you may want to improve your grill’s efficiency by checking for leaks or cleaning the burners to achieve a clear blue flame (see “Grill Cleaning, Maintenance, and Repair,” facing page).
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Gas
Charcoal grills can be as simple as a metal box and a metal grill grate, but even a single-burner gas grill is much more complex. You still have the basics: fuel, ignition source, and oxygen. But the difference in fuel changes everything, because vaporous gas has a relatively narrow range of flammability.
A gas grill’s fuel, whether a tank