Aluminium vs Titanium

Aluminium is the most abundant metal in the Earth's crust, yet two hundred years ago nobody had seen a piece of it. It clings so tightly to oxygen that separating it needed chemistry that did not yet exist. Then cheap electricity changed everything, and today it is the second most used metal in the world.

• In the 1850s aluminium cost more than gold, and Napoleon III is said to have served his most honoured guests with aluminium cutlery.
• The small pyramid on top of the Washington Monument, set in 1884, is made of aluminium, then a showpiece metal.

Titanium is the metal of hip replacements, jet engines, racing bikes and the white in almost every tin of paint. It combines strength with lightness and shrugs off seawater and body fluids, thanks to a thin, tough oxide skin that forms the instant it meets air.

• Klaproth named titanium after the Titans of Greek myth; he had named uranium after the planet Uranus a few years earlier.
• The SR-71 Blackbird spy plane was built largely from titanium because aluminium would have softened at the temperatures reached in flight.