Liquid soap or neutral detergent
Household liquid soap (fatty acid salts) or neutral detergent (synthetic surfactant).
Characteristics
- Soap is made by saponifying fats with sodium or potassium hydroxide.
- Its amphiphilic molecules lower the surface tension of water.
- In hard water soap forms insoluble scum; detergent hardly does.
- Household detergents contain roughly 10 to 20 % surfactant.
Role in the preparation: Acts as a wetting and emulsifying agent that helps the mixture spread evenly.
Caution: Avoid eye contact, prefer products without perfume or additives, expect foaming and check local regulations before any use.
Sources: Purdue Extension WS-7 - Adjuvants and the power of the spray droplet · Science ABC - Difference between soaps, shampoos and detergents
Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.