Why Are Drink Cans Made of Aluminium?

Step 1 of 5

It is very light.

The same size lump of aluminium weighs about a third of what steel does. That is why it is used for cans, foil, bicycle frames and most of an aeroplane.

Step 2 of 5

It does not rust — it seals.

Aluminium reacts with air instantly. But instead of flaking like rust, it forms a hard transparent skin only a few atoms thick that seals the surface and stops anything getting further in.

Step 3 of 5

It was once worth more than gold.

The metal is everywhere in ordinary clay and rock, but it is bonded so tightly that nobody could get it out. For a while a bar of aluminium was a royal curiosity, more prized than gold.

Step 4 of 5

Electricity is what freed it.

The way out was to melt the ore and push a huge electric current through it, dragging the aluminium loose. It works, but it takes an enormous amount of power — smelters get built next to dams.

Step 5 of 5

Recycling it saves nearly all of that.

Melting a used can needs about a twentieth of the energy of making new metal from rock. That is why aluminium recycling actually pays for itself, and why a can can be back on a shelf in weeks.

Aluminium foil has a shiny side and a dull side only because two sheets are rolled together at the last step. It makes no difference which way up you use it.