On Food and Cooking

never found in nature in the pure state, and a
good method for separating the metal from its
ore wasn’t developed until 1890. In cookware,
it is usually alloyed with small amounts of
manganese and sometimes copper.
Aluminum’s prime advantages are its
relatively low cost, a heat conductivity second
only to copper’s, and a low density that makes
it lightweight and easily handled. Its
ubiquitous presence in the form of foil
wrappings and beer and soft drink cans
testifies to its usefulness. But because
unanodized aluminum develops only a thin
oxide layer, reactive food molecules — acids,
alkalis, the hydrogen sulfide evolved by
cooked eggs — will easily penetrate to the
metal surface, and a variety of aluminum
oxide and hydroxide complexes, some of them
gray or black, are formed. These can mar
light-colored foods. Today, most aluminum
utensils are either given a nonstick coating or
are anodized, a process that involves making