About the blog: What Things Are Made Of


The United States relies on imports for dozens of commodities in everyday use. Often enough, that reliance is 100%. In this book I aim to provide awareness of the hidden geology and mineralogy behind common things, and to develop an appreciation for the global resource distribution that underpins our society. While concerns about oil import reliance are in the news every day, our needs for other minerals are comparable and are typically unknown even to technologically aware Americans.

Saturday, February 13, 2010

Toast for breakfast

How many nations do you depend on when you toast your morning bread?

My cheap $15 toaster’s case is mostly galvanized (zinc-coated) steel, with white exterior surfaces thanks to a thin enamel covering. Common traditional toasters, many still in service, are chrome-plated steel. The ends of mine are white plastic with red lettering.

The bread rack inside is also chrome- or nickel-plated steel, although in mine there’s also an aluminum support system. Stainless-steel (a chromium-iron alloy) screws and rivets hold the whole thing together. A nickel-chromium alloy, in strips wrapped around a mica sheet or mica-paper board, does the work. Nickel-chromium has high electrical resistance—it doesn’t conduct electricity well, so when a current flows through it, it gets hot.

Differential thermal conductivity comes into play again, in the thermostat, which may be a simple bi-metallic strip (usually steel and copper). The two metals heat up at different rates, forcing the strip to bend. This action in turn effectively flips a switch to turn off the heat and release the rack so it pops up.

The wire that leads to the electric outlet is copper, insulated by flexible plastic.

Some of the raw materials that make the toaster come from domestic mining, but the U.S. depends on imports for most of the materials.

Bauxite (aluminum ore) – 100% dependent (from Jamaica, Brazil, Guinea, and 5 others)
Nickel – recycling + imports = 72% (from Canada, Russia, Norway, and 18 other countries)
Chromium – recycling + imports = 100% (from South Africa, Kazakhstan, and 12 other countries)
Mica – 16% (from Canada, China, India)
Oil and refined products for plastics – 58% (Canada, Mexico, Venezuela, Saudi Arabia, and 64 other countries)
Titanium dioxide pigment – U.S. exports, but depends on 77% imports for titanium metal (South Africa, Australia)
Antimony (flame retardant in plastic) – 86% dependent (China)
Copper – 33% to 43% dependent (from Chile, Canada, Peru, and 12 others)
Zinc for galvanizing iron – 73% dependent for zinc metal (Canada, Mexico, Korea)
Iron ore – U.S. just about breaks even: a small exporter some years, a small importer in other years.

We’ll save the bread itself, together with the electricity to run the toaster, for future posts.

So how many countries in your toaster? Canada, India, South Africa, Russia, Norway, Mexico, Kazakhstan, Chile, China, Jamaica and the U.S. – eleven countries at a minimum.

Photo by Donovan Govan, used under the GNU Free Documentation License.

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