Should I use powder, liquid or capsule detergent?

Detergent choice is usually treated as a brand question, and the useful distinction is the format, because format determines chemistry. Once you know what is in each, the right one for a given load is obvious.

Safety

Step by step

1. Understand what is in powder.Surfactants, enzymes, water softening builders such as zeolites, and — crucially — an oxygen bleach system that only works in powder, because it is not stable in a liquid. Powder also contains optical brighteners in most white formulations.
2. Understand what is in liquid.Surfactants and enzymes at higher concentration, with no bleach and usually fewer builders. Liquid dissolves instantly, works well in cold water, and is markedly better on greasy and oily soil, which is most everyday body soil.
3. Understand what a capsule is.A pre-measured dose of concentrated liquid in a water-soluble film. Same chemistry as liquid, with the convenience of no measuring and the drawback of no adjustment for a small, lightly soiled load or for soft water.
4. Use powder for whites, bedding and towels.The bleach system removes tea, coffee, wine, fruit and grass stains that liquid leaves behind, and it is the reason whites washed in liquid gradually go grey. It also keeps the machine cleaner.
5. Use liquid for colours, dark clothes and greasy soil.No bleach means no colour loss and no optical brighteners depositing a dulling film on black. It also handles collar grime, cooking oil and sportswear better.
6. Choose bio or non-bio by what is in the load.Biological detergent contains enzymes that break down protein, starch and fat stains and works well at low temperatures. It must never be used on wool or silk, because it digests them. Non-bio for those fibres, and for anyone whose skin reacts.
7. Keep a wool wash for protein fibres.A dedicated wool and silk detergent is pH-neutral, enzyme-free and mild. It is not interchangeable with non-bio liquid, which is still alkaline enough to matter over time.
8. Dose by hardness, load size and soil, not by habit.The dose on the pack assumes a full, heavily soiled load in hard water. In a soft-water area with a half load, you need substantially less. Overdosing leaves residue that stiffens fabric, holds odour and feeds the smell in the machine.

Tips

• Powder that clumps has absorbed moisture and its bleach system is degrading. Keep it sealed and dry, and do not buy more than you will use in a few months.
• In a hard-water area, powder's builders do real work that liquid does not, and the difference in results on whites is visible.
• Capsules must go in the drum at the back, before the clothes, not in the drawer. In the drawer the film does not dissolve properly and the dose is wasted.
• A separate stain remover applied to the mark beats any detergent applied to the whole load. Detergent is for general soil.
• If your washing smells even when clean, the answer is usually less detergent and a hot maintenance wash, not more detergent.

Common mistakes

• Using a colour liquid on white cotton bedding — There is no bleach in it, so tea, sweat and body soil accumulate and the whites go grey. This is the most common cause of dingy whites.
• Using capsules for every load regardless of size — A half load of lightly worn shirts gets a full dose, and the excess deposits on the fabric rather than rinsing away.
• Using biological detergent on a wool jumper because it was only a delicate cycle — The cycle protects the garment from agitation. The enzymes attack the fibre chemically regardless of how gently the drum turns.

Alternatives

• Laundry sheets and strips: Dissolvable sheets of concentrated detergent. Convenient and light to post, but with less cleaning power per wash than a full liquid dose and no bleach system. Reasonable for light loads, weak on stains.
• Soap nuts and eco balls: Sold as detergent replacements. Soap nuts release a small amount of natural saponin, which has a mild effect on light soil; eco balls have no established cleaning mechanism. Neither performs like detergent on real soil, and they do nothing for whites.
• Bar soap and a soak: For hand washing and for pre-treating collars, a plain soap bar or a dedicated stain bar worked into the fabric is genuinely effective — soap is a surfactant, which is the active ingredient in everything above.

Questions people ask