Colour in a detergent or cleaner signals freshness and brand, but these products are harsh environments for colorants.
The main stresses
- pH: laundry liquids and powders are alkaline, many cleaners acidic
- Oxidants: percarbonate, hypochlorite and peroxide bleach many dyes
- Light: transparent bottles on a shop shelf expose liquids to daylight for months
- Surfactants and perfume: can shift shades or cause precipitation
Choosing the colorant type
Soluble dyes give clear, transparent liquids. Pigment dispersions suit opaque products and give better light fastness. Speckles colour a fraction of a powder for visual effect. Fabric staining must also be checked: a laundry colour must never transfer to clothes.
Testing
Store samples of the finished product at elevated temperature and under light alongside dark controls, and check shade after several weeks.
