6 Stains Most People Set Permanently — and the Right Way to Lift Them · 2 of 6

2. Blood: cold water and enzymes, never heat

Blood is a protein stain, and protein coagulates with heat. Hot water on blood is the single most reliable way to make a stain permanent — it cooks the protein into the fibre exactly as an egg sets in a pan.

Fresh blood usually comes out with nothing but cold water. Hold the fabric under a cold tap from the back and let the flow push it out. For a soaked patch, fill a bowl with cold water, submerge and agitate gently with your fingers, changing the water when it colours. Most fresh blood is gone within ten minutes.

Dried blood needs enzymes. Soak in cold water with a biological laundry detergent — one listing protease among its enzymes — for at least an hour and up to overnight. Enzymes digest the protein into fragments small enough to rinse away. On a stubborn dried spot, work a little neat biological liquid into the fabric with a fingertip and leave it fifteen minutes before the soak.

Hydrogen peroxide at 3 percent, the strength sold in pharmacies, works well on white cotton: dab it on, watch it foam, then rinse in cold water. Keep it off coloured fabric, wool and silk, where it will lighten the dye and damage the protein fibres.

For mattresses and upholstery you cannot rinse, make a paste of cornflour, cold water and a little salt, spread it thickly, let it dry completely, then brush and vacuum it away.