There’s soap for us all...
QUESTION What is the chemical difference between expensive handwash and cheap washing-up liquid? All washing products are essentially the same.
They use the cleansing power of surfactants — chemical compounds that reduce the surface tension between two liquids or a liquid and a solid.
They are made up of two parts: one is hydrophilic (attracted to water); the other is hydrophobic (repelled by water).
The hydrophobic parts attach themselves by means of electrical attraction to any surface other than water.
At the same time, the hydrophilic parts pull away from the material and toward the water.
Using a brush or rubbing with your hand breaks up the dirt.
The agitation also helps to pull the dirt particles from the material and into the water. These remain suspended in the water until they are rinsed away. Despite the fact that all washing products rely on surfactants, you would be advised not to use a cheap washing-up liquid to wash your hair.
The surfactant in washing-up liquids is too efficient: perfect for greasy plates, but it would strip your hair of protective natural oils, leaving it dry and brittle.
Shampoos and milder soaps contain a weak surfactant, such as sodium lauryl sulphate.
Aside from the differences in surfactants, there is a bewildering array of additives, antibacterial agents, thickeners, preservatives, emulsifiers, colour additives, vitamins, strengthening agents, foam boosters and perfumes that give each cleaning product a unique character and affect its price.