How do I remove yellow sweat and deodorant marks from shirts?

Antiperspirant works by depositing aluminium salts that plug the sweat duct. Those salts combine with the protein and salt in sweat and with the fibre itself, building a stiff yellow crust that ordinary washing cannot dissolve because it is neither grease nor dirt. It needs an acid to break the mineral bond and an enzyme to digest the protein.

What you'll need

• White vinegar
• Bicarbonate of soda
• Biological detergent
• An old toothbrush

Step by step

1. Turn the shirt inside out.The deposit is on the inside face of the fabric where the deodorant sat. Treating the outside is treating the wrong side of the problem.
2. Soak the armpits in white vinegar and warm water.One part vinegar to two parts water, for an hour. The acid dissolves the aluminium salts that make the crust rigid.
3. Make a bicarbonate paste and work it in.Three parts bicarbonate to one part water, spread over the wet area and worked in with an old toothbrush. Leave it thirty minutes.
4. Never use chlorine bleach on it.Bleach reacts with the sulphur-bearing proteins in sweat and turns a pale yellow mark distinctly darker. It is the commonest way a rescuable shirt is finished off.
5. Wash warm with a biological detergent.Forty degrees. The enzymes handle the protein part of the deposit that the acid and the alkali between them have loosened.
6. Check before drying.If the yellow has faded but not gone, repeat the whole sequence. Heat from a dryer or an iron sets what is left and stiffens it again.
7. Deal with the stiffness separately.Fabric that crackles under the arm has mineral build-up through the weave, not just on it. An overnight vinegar soak of the whole garment softens it.
8. Change the routine that causes it.Let antiperspirant dry fully before dressing, use less of it, and wash shirts after every wear. Build-up is cumulative and the marks appear after months, not days.

Tips

• An aluminium-free deodorant stops new marks appearing entirely, though it does not stop sweat itself.
• Wash shirts promptly. Sweat left in cotton for a week oxidises and the yellowing becomes far harder to reverse.
• White cotton shirts benefit from an oxygen bleach soak after the vinegar and bicarbonate — but never chlorine bleach on this particular stain.

Common mistakes

• Using chlorine bleach on underarm yellowing — It darkens the stain rather than lifting it, because it reacts with the proteins in dried sweat. Many shirts are thrown away because of this single step.
• Mixing the vinegar and bicarbonate together first — They neutralise each other into salty water. Used one after the other they each do their job; used together they do nothing but fizz.

If it doesn't work

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