A stain on a secondhand garment is a puzzle with two unknowns: what made it, and how long it has been there. The second unknown matters more. Fresh marks are mostly a matter of lifting a substance out of the cloth, while old ones have often bonded to the fibre or been set by heat, and the difference between a stain that disappears and one that never will comes down to which of those two situations you are dealing with.
This is not a reason to refuse every marked garment. It is a reason to identify the mark before you treat it, to test your method on a hidden area before applying it to the front, and to accept that a few categories of damage are permanent by the time you find them on a rack.
The type of stain decides the method
Cleaning works by matching a solvent to a substance. Water dissolves sugar and salt; detergent lifts oils; enzymes digest proteins and starches; oxidising agents break the chemical bonds that give a stain its colour. Use the wrong one and you either do nothing or set the mark in place.
- Protein stains — blood, egg, milk, sweat — are the ones heat ruins. Hot water coagulates them the way it cooks an egg, and once that has happened the mark is bonded to the fibre. Treat these cold.
- Oil and grease stains — cooking oil, cosmetics, machine grease — come out with detergent and warmth, and benefit from being broken up before washing.
- Tannin stains — tea, coffee, wine, fruit juice — respond to oxygen bleaches and to ordinary detergent, but not to heat.
- Ink, dye and marker marks are solvent problems rather than water problems.
- Rust is not a stain in the usual sense. It is metal that has transferred into the cloth and oxidised there, and it needs an acid to dissolve it.
- Yellowing along folds and underarms is oxidation of the fibre or of residues left in it. It responds slowly to oxygen bleach and to light, and it is often the hardest thing on this list.
Test before you treat
Find a hidden area: an inside seam allowance, the inside of a hem, the back of a facing. Soak a cotton bud or the corner of a white cloth in whatever you intend to use, press it onto the fabric, and wait a minute. You are checking two things at once, whether the colour runs and whether the fabric weakens or loses its finish.
Run the test on every part of the garment that differs: the main fabric, the lining, the trim, the thread. A method that is safe on a plain cotton shirt can strip the colour from a contrasting collar or dull a metallic thread, and the damage will be in the most obvious place.
Working through the stain types
Protein
Rinse the mark under cool running water from the back of the fabric, so you push the substance out the way it came in rather than driving it deeper. Work a little enzyme detergent into the fibres with your fingertips, leave it a few minutes, and rinse again. Only once the mark has lightened should you wash the garment normally. Keep hot water out of the process at every stage.
Oil and grease
Blot rather than rub, and scrape off anything solid first. Apply a small amount of washing-up liquid or a dedicated grease remover directly to the mark, work it in gently, and let it sit before washing. On old, dry-set grease marks, a second application after the first wash often lifts what the first round loosened, so do not judge the result until the garment has dried.
Tannin
These respond well to an oxygen-based bleach, the kind sold as a powder that fizzes into warm water. Dissolve it fully before the garment goes in, then soak. Test first on coloured items, because oxygen bleach is gentler than chlorine but is not safe on every dye.
Ink
Fresh ink can sometimes be lifted by applying alcohol to the underside of the fabric with an absorbent pad behind it, so the ink is drawn out rather than pushed through. Old ink that has been through a dryer is usually permanent. If the ink has spread to the reverse of the cloth, expect a shadow to remain.
Rust
A mild acid such as lemon juice or white vinegar will dissolve light rust, but acid also attacks cotton and linen if left on too long, and it can dull some dyes. Keep the treatment local, rinse thoroughly, and neutralise afterwards. On a valuable garment this is a job for a specialist or not a job at all.
Yellowing
Soak in oxygen bleach and dry in daylight, and repeat over several sessions rather than trying to force a result in one. Underarm yellowing is often a mixture of oxidised antiperspirant residue and body oil, which needs the grease step before the oxygen step.
Marks that will not come out
Some marks are not stains at all, and no method will shift them.
- Dye migration, where a dark garment has bled into a light one, is colour that has moved into the fibre. Bleaching it removes the base colour as well.
- Bleach damage is the absence of dye, not the presence of a stain.
- Rust that has sat in the cloth long enough to rot the fibre leaves a hole behind even if the colour goes.
- Heat-set scorch marks and melted synthetic fibre never lift.
- Marks that have been through a tumble dryer repeatedly are often chemically bonded and should be treated as permanent.
Judging a stain before you buy
At the rack you can make a reasonable guess about whether a mark will wash out, and the useful checks are all observational.
- Look at the edges. A mark with a hard, dark outline has been there a long time and has dried in place; one with soft edges is more likely to be recent.
- Smell it. Grease, perfume and smoke all announce themselves, and each points to a different method.
- Feel it. Crusty or stiff patches are dried solid; flat, discoloured areas are usually dye or oxidation.
- Check the fibre. A protein mark on a delicate or dry-clean-only garment is a poor bet, because you cannot give it the water and time it needs.
- Ask what made it, if the seller knows. An honest “I do not know” is a reason to price the risk in rather than an obstacle.
When to leave it behind
If the fabric is already thin, or the garment is lined and structured, a treatment that involves soaking and agitation may cost you the garment in order to save the mark. If the stain sits on silk that has gone brittle, or on a piece with a fragile surface finish, the sensible answer is either to buy it only if the mark does not bother you, or to walk away.
Decide which outcome you can live with before you start, because the treatment is the irreversible step. A mark you cannot see from conversational distance is not always worth the risk of ruining an otherwise sound piece, and the calm choice is usually to weigh the garment rather than the stain.