Cast iron and carbon steel

What it is

Cast iron is iron with a few per cent of carbon, poured into a mould. Carbon steel has less carbon and is pressed or spun into thinner, lighter pans, such as woks and crêpe pans. Both are metal, so neither is plastic under our definition.

Bare iron rusts, so these pans are seasoned: a thin layer of cooking oil is baked on until it forms a hard, dark coating. It builds up with use and gives the pan a slick surface. That's what makes iron a realistic swap for non-stick pans, whose coatings are a fluoropolymer plastic (PTFE).

This page covers bare and seasoned iron. Enamelled cast iron, which has a glass coating, behaves differently.

Does iron get into food?

Yes, and that's often seen as a benefit. Iron moves from the pan into food, and how much depends on the cooking:

• A laboratory study of iron pots found more iron was released at higher temperatures, with longer cooking times, and with more acidic food. The authors note that the World Health Organization has identified iron cookware as a possible way to tackle iron deficiency anaemia.
• In a small trial, snacks cooked in iron pots had about 16% more iron than the same recipes cooked in non-stick pans, and the children who ate them had a rise in haemoglobin over four months.

Most adults get enough iron from food. If you have a condition that raises iron levels, such as haemochromatosis, or you've been told to limit iron, ask your GP or a dietitian whether iron cookware matters for you.

Because acidity and long cooking release the most iron, you may prefer steel or enamel for long-simmered acidic dishes such as tomato sauce.

How to use it well

• Dry it straight after washing, then wipe on a thin layer of oil.
• A little washing-up liquid is fine; don't soak it or put it in the dishwasher.
• If it rusts, scrub the rust off and re-season.
• Handles get hot, so use a cloth or a natural-fibre handle sleeve. Some pans have plastic handles, so check before buying.

Recycling

Iron and steel are infinitely recyclable. Look after a pan and it can outlast you; if one does crack, take it to the scrap metal container at your local tip.