Lye

Other Name(s):

Sodium Hydroxide; Potassium Hydroxide; Caustic Soda; Potash; Sodium Hydrate; Potassium Hydrate

Sodium Hydroxide (the most commonly used lye) is made as a byproduct of chlorine production using rock or sea salt (NaCl) as a starting material. The chlorine atoms are split from the salt using electrolysis.

Is Lye Faithful to Nature?

Depends.

Lyes are natural ingredients which have been used to make soap as far back as 2800 B.C.

Benefits: Why is Lye used?

Starting Material of Soaps

Lyes are used in the saponification reaction of vegetable and animal fats.

Alkalising

Lyes are used to neutralize or to lower acidity of products intended to have an alkaline pH.

Household Uses

Sodium Hydroxide (caustic soda) is used to clear clogged drains.

Food Application

Lye is used in a number of foods as a curing agent.

Learn more about Lye:

On the Shelf: Which Products Use Lye?

Lye is used in the making of solid and liquid soaps, as such it may appear on ingredient lists for soap bars, handwashes, castile soaps, and any other cleaning products which don’t make use of chemical detergents.

Production: How is Lye Made?

The various lyes used in commercial products are made by oxidation of sodium or potassium.

Interesting Fact: Lye

Sodium Hydroxide and Potassium Hydroxide are listed in the Cosmetics Directive of the European Union and may be used at the following concentrations and pH values: 5% by weight in nail cuticle solvents, 2% by weight in hair straighteners for general use, 4.5% by weight in hair straighteners for professional (salon) use, up to a pH 12.7 in hair removal products, and up to pH 11 in other uses as a pH adjuster.

Professional soap makers are careful to ensure that their final product’s pH does not exceed 9-10. If the soap is more basic than this, it can irritate the skin.

Lyes fully react with oils, when the correct balance or a superfat percentage is used, and none remains present in a carefully produced soap product.