The shiny metallic aluminum also has a matte side

The leftover potato gratin in my refrigerator has one thing in common with the Washington Monument: there’s aluminum on top. Without ceremony, the aluminum fell onto the baking dish, just seconds after a piece of foil was torn from the roll which was then dumped at the bottom of the kitchen cupboard. Aluminium “hatThe Washington Monument, on the other hand, was widely displayed by the manufacturer in the window of the Tiffany jewelry store in New York before it was installed — a move that angered Washington.

The monument’s point – 22 centimeters high, three kilograms – was placed in 1884. Aluminum was more expensive than silver at the time. The baking dish was covered after 140 years, and a roll of 30 meters of aluminum foil cost €2.66. Thanks to two manufacturing processes discovered shortly after the completion of the Washington Monument, aluminum has become astonishingly cheap.

Aluminum (Al, number 13 on the periodic table) is a soft metal. More than 8% of the Earth’s crust consists of aluminum, but it does not exist in pure form. As part of aluminum oxide and potassium aluminum sulfate. The existence of the element was first suspected in 1807, but techniques to isolate the element were not available until 1825. That honor goes to Danish chemist Hans Christian Oersted.

In 1886, chemists Charles Martin Hall and Paul Herault improved the process of extracting aluminum from alumina using electrolysis. A year later, Karl Joseph Bayer also devised an improved process for extracting aluminum oxide from bauxite, by treating the ground bauxite with warm sodium hydroxide (an aqueous solution of sodium hydroxide). Then the price per kilo fell from 30 guilders in 1880 to 0.75 guilders in 1911, the Aluminum and Stainless Steel Industry Journal wrote.

Overuse and pollution

Aluminum is now the most widely used metal in the world after steel. This does come with the price. Production processes are energy-intensive: aluminum production represents 1% of total global greenhouse gas emissions. The environment is also suffering. The Bayer process with sodium hydroxide produces a residual slurry stream called red clay—after the red color of iron oxide. For every ton of aluminum, more than a ton of red clay, with a pH between 11 and 13, is created. Therefore, it is highly alkaline and the sedimentation basins in which it is stored pose an environmental problem.

Aluminum in its pure form is very soft. Mixing it with other metals gives it strength. Even for covering food, pure aluminum will be very smooth. This is why half a percent of iron is added to aluminum foil.

To conclude one Fun fact: Aluminum foil usually has a glossy side and a glossy side because two layers of foil are wrapped at the same time. This is done to prevent tearing of the thin material. After rolling, the layers are separated again. The shiny side was in contact with the cylinder, and the matte side was in contact with the other layer of foil.

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