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Soft wash mix ratio (sodium hypochlorite)

The soft wash mix ratio (SH mix ratio) is how much sodium hypochlorite is diluted with water for a soft wash, worked out from the product's strength and the strength you want at the surface.

Also called
  • sodium hypochlorite mix ratio
  • SH mix ratio
  • SH mix
  • SH ratio
  • bleach mix ratio
  • soft wash mix
  • chlorine mix

Sodium hypochlorite (SH) is the active ingredient in bleach and the main cleaner in soft washing. Products are sold at different strengths, printed on the label as a percentage, so the same "1 to 1" mix gives very different results depending on what is in the jug. Work from percentages, not ratios.

The target strength depends on the surface and how heavy the growth is. Follow the chemical's label and the surface maker's guidance: for shingles, for example, the Asphalt Roofing Manufacturers Association describes a household bleach and water solution (ARMA). Wear the protective gear the label calls for, and protect plants and people nearby.

Never mix SH with acids or ammonia

Bleach mixed with acids (such as some rust removers) or ammonia releases dangerous gases. Read every label before combining products in a tank.

Formula

C1 × V1 = C2 × V2
SH needed (V1) = target strength (C2) × batch size (V2) ÷ product strength (C1)
water = batch size − SH needed − surfactant
C1 is the product's strength from the label, C2 the strength you want, V2 the batch size.

Example

To make 10 gallons at 1% from a product labelled 12.5%: 1 × 10 ÷ 12.5 = 0.8 gallons of SH, plus about 9.2 gallons of water (less a little for surfactant). The numbers are an arithmetic example; your label and surface decide the target.

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