Alkali Types

Alkali's are those substances which possess a pH greater than 7 and can thus act to neutralize acids by formation of the corresponding salt. In the case of fatty acids, the corresponding salts formed are "soaps".

In practical terms for soapers alkalis are basically divided into :

Sodium Hydroxide - NaOH (aka "Lye" or "Caustic Soda")

 A white powder or prill which is intensely alkaline and normally 98 - 99% pure, the other 1% being traces of carbonate and water that are generally regarded as insignificant in soap manufacture. Probably the best known and most widely available alkaline salt, sodium hydroxide is used in the manufacture of "hard" soaps (cf. potassium hydroxide). The product generates significant heat when mixed with water and appropriate care should be taken when mixing and using the product (glasses/goggles, rubber gloves). Contrary to popular belief, a 50% solution of Sodium Hydroxide can be stored for extended periods without loss of activity - providing it is stored in a well sealed plastic (HDPE) container with minimum air space above the solution. The product must not be stored in glass as both the solid and the solution are corrosive to glass and will lose activity over time

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Potassium Hydroxide - KOH (aka "Potash Lye" or "Caustic Potash")

A white flake or prill which is intensely alkaline and usually of 90 - 95% purity, the remainder being potassium carbonate. Potassium hydroxide is used to produce "soft" or "liquid" soaps and was often used in the manufacture of shampoos prior to the development of synthetic detergents. The product generates significant heat when mixed with water and appropriate care should be taken when mixing and using the product (glasses/goggles, rubber gloves). Like NaOH, a 50% solution of Potassium  Hydroxide can be stored for extended periods without loss of activity - providing it is stored in a well sealed plastic (HDPE) container with minimum air space above the solution. The product must not be stored in glass as both the solid and the solution are corrosive to glass and will lose activity over time. Note that the product is significantly more expensive than sodium hydroxide due to recent market price rises.

Toiletries manufacturers may also use a number of other alkalis, particularly when formulating lotions. Typically, these would include :

Carbonates, in particular sodium carbonate ("soda ash") and sodium peroxycarbonate ("sodium oxygen bleach" "coloursafe bleach").

Organic Amines, in particular diethanolamine and triethanolamine.

Price on application.