What does fabric conditioner actually do, and when should I skip it?

Fabric conditioner is a cationic surfactant — a positively charged molecule that clings to the negatively charged surface of washed fibre and lies flat on it. That is why clothes feel smooth and why static disappears. Everything good and everything bad about the product follows from the same coating.

What you'll need

• A washing machine with a conditioner drawer
• White vinegar, as an alternative (optional)

Step by step

1. Know what the coating does.It lubricates fibres so they slide over each other, which reads as softness, reduces creasing and stops static. It also fills the spaces between fibres.
2. Keep it off towels.Towels work by absorbing water into the fibre. A waterproof-ish coating is the opposite of what a towel needs, and after a few washes they push water around rather than soaking it up.
3. Keep it off activewear and technical fabric.It blocks the wicking structure and traps body oil underneath, which is the main reason gym kit smells permanently.
4. Keep it off waterproofs.It destroys the durable water repellent finish on a coat and clogs breathable membranes. Waterproofs need a specialist wash, not conditioner.
5. Never use it on flame-resistant nightwear.Children's nightwear sold as low flammability relies on a finish that fabric conditioner coats over and compromises. The care label will say so.
6. Keep it off microfibre cloths.Microfibre works by having an enormous surface area of fine split fibres. Coating them fills the splits and the cloth stops picking anything up.
7. Use it where it genuinely helps.Cotton bedding, shirts that crease badly, and anything prone to static. Half the recommended dose is usually enough.
8. Try white vinegar as a substitute.About 60ml in the conditioner drawer. It strips detergent residue, softens water, reduces static and leaves no coating. There is no vinegar smell once dry.
9. Watch for build-up in the machine.Conditioner residue is a major contributor to the slime in a detergent drawer and door seal. Clean the drawer monthly if you use it.

Tips

• If towels have already gone water-repellent, wash them twice with no detergent and a cup of white vinegar to strip the coating back off.
• Dryer sheets do the same thing as liquid conditioner and carry the same warnings — particularly on towels and technical fabrics.
• In a soft water area you need much less of everything, including conditioner. Doses on the bottle assume hard water.

Common mistakes

• Using it on towels to make them softer — It makes them feel softer and absorb far less. The correct fix for hard towels is less detergent, a proper rinse and a short tumble or a good shake, not a coating.
• Using it on waterproof coats and technical kit — It strips or masks the water-repellent finish and blocks the breathable membrane, converting an expensive coat into a jacket that wets out in light rain.

If it doesn't work

Questions people ask