Too Much Detergent Is Why Your Towels Smell

Both approaches to detergent dosing work. What differs is what they cost you, and the cost is what this sets out.

What detergent actually does

Detergent works through surfactants, molecules with one end attracted to water and one attracted to oil and grease. They lift oily soil off fibres and hold it suspended in the water so it drains away rather than settling back onto the fabric.

Modern detergents also contain enzymes that break down specific soil types such as protein, starch and fat. Those enzymes work best in a particular temperature range, which is why very hot washes can be less effective on protein stains than warm ones. The whole system depends on the detergent being rinsed away afterwards, which is where overdosing breaks it.

Why more makes things worse

A machine uses a fixed volume of water in the rinse cycle, and beyond a certain point that water cannot carry away any more surfactant. The excess stays in the fabric as residue, which is sticky, holds onto soil and provides something for bacteria to feed on.

That residue is the usual cause of towels that smell musty within a day of use, despite being freshly washed. It also makes fabric feel stiff and reduces absorbency, which people then attribute to the towels themselves being old. Excess foam is a further problem, since it cushions the clothes and reduces the mechanical action that does part of the cleaning.

Dosing correctly

The dose on the packet is stated against water hardness and load size, and both matter more than how dirty the wash looks. Hard water contains minerals that bind to surfactants and reduce their effectiveness, which is the reason hard water areas need more.

In soft water areas the correct dose is often well below what people habitually use, sometimes half. Find out your local water hardness, which water suppliers publish, and dose from the corresponding column rather than from habit. Measure it rather than eyeballing it, because the difference between a correct dose and double is invisible in the drawer.

Fixing clothes that already smell

Run a wash with no detergent at all at the highest temperature the items allow, which rinses accumulated residue out of the fibres. Repeat until no foam appears during the wash, which for badly affected towels can take more than one cycle.

Then resume washing with a correct dose, and the smell generally does not return. Wet laundry left in the drum for hours develops a smell through bacterial growth, which is a separate cause with the same symptom.

Drying promptly and completely is as important as the wash itself, since fabric that dries slowly is fabric that smells.

Softener, and whether you need it

Fabric softener works by depositing a lubricating layer on fibres, which is what makes fabric feel smooth and reduces static. That coating also reduces absorbency, which makes it a poor choice for towels and for technical or sportswear fabrics. It builds up over time, contributing to the same residue problem and to the persistent smell in items washed with it repeatedly.

Cooking for one, white vinegar in the rinse is a common alternative that helps strip residue, though it should never be combined with bleach products. For most one-person laundry, skipping softener entirely causes no problem at all and solves several.

Leave gas, mains electrics and anything behind a wall to someone qualified and insured.

Powder, liquid and capsules

Powders generally contain bleaching agents that work on stains and whites at higher temperatures, which liquids usually omit. Liquids dissolve reliably at low temperatures and are better on greasy and oily marks, which is why many people keep both.

Once the deposit is down, capsules are pre-dosed for an average load in average water, which means they are wrong for anyone with a small load or soft water. Undissolved powder residue on clothes usually indicates a cold wash, an overloaded drum or a blocked detergent drawer. Whatever you use, store it sealed and dry, since powder that has absorbed moisture clumps and doses unpredictably.

Side by side

The takeaway

Use less than you think, check your water hardness, and skip the softener on towels entirely.

Do the ten-minute version tonight rather than the proper version never.