Zinc vs Tin

Zinc has a habit of doing its work unseen. It coats steel lampposts, crash barriers and roofing so they do not rust. It sits alongside copper in brass door handles, in the cases of alkaline batteries and in the cores of modern pennies. Inside your body, around three hundred enzymes need zinc to function, including ones involved in growth, immunity, wound healing and the senses of taste and smell.

• Zinc boils at a lower temperature than is needed to smelt its ore, so early European furnaces turned it straight into vapour that burned away in the flue.
• The Zawar mines in Rajasthan were producing zinc metal in sealed retorts centuries before Europe worked out how.

Around five thousand years ago, someone in the ancient Near East mixed a little tin into molten copper and produced a metal harder and easier to cast than either. That alloy, bronze, gave its name to an entire age of human history. Tin has been in continuous use ever since, and it may be the least glamorous of the truly essential metals.

• A bar of pure tin makes a crackling sound when bent, called tin cry, as its crystal structure deforms.
• Below about 13 °C, white metallic tin slowly transforms into a brittle grey powder, a change known as tin pest that can crumble old pewter and tin objects.