What Is Lye Used For?

Reviewed on 2/17/2021

 Lye is used to cure many types of food.
Lye is used to cure many types of food.

Lye has several uses and is used for the following:

  • Food industry: Lye is used to cure many types of food. Curing is the process of partially cooking meat.
  • Soap making: Lye in the form of both sodium hydroxide (NaOH) and potassium hydroxide (KOH) is used in making soaps. Lye is added to water, cooled down for a few minutes, and then added to oil and butter. This is then cooked for 1-2 hours and then placed into a mold to make soap bars of various shapes. A soap without lye is technically not a soap.
  • Making of household and industrial products: Lye is used to make commercial and industrial cleaners and clogged drain openers because of its cleaning effects and ability to dissolve grease.
  • Tissue digestion: NaOH or KOH can be used to digest tissues of animal carcasses. The process is done by placing the animal carcass or body into a sealed chamber and adding a mixture of lye with water. Heat is then applied to accelerate the process. After several hours, the animal body turns into a liquid with coffee-like appearance, and the only solids that remain are fragile bone bits that can be easily crushed mechanically into a fine powder with very little force.
  • Fungus identification: A solution of 3-10% KOH is used to identify the presence of fungus in samples of body tissue or body secretions/fluids. This is also called KOH staining.

How is lye made?

Traditionally, lye soaps were made by boiling wood ash. The lye was then skimmed off the top. Lye can also be made from sodium bicarbonate (baking soda) and calcium oxide.

However, these methods of making lye yielded inconsistent lye. Nowadays, lye is made using normal salt (sodium chloride [NaCl]).

The process of making lye involves the following:

  • Salt is dissolved into water, and the alt crystals sink to the bottom of the container.
  • Graphite rods are inserted into the mixture.
  • Current is then passed through the rods.
  • The sodium splits from the chlorine (NaCl: common salt), and it reacts with hydrogen in water forming lye.
  • Lye crystals get charged and get attached to the graphite rods.
  • The liquid is then poured off and allowed to evaporate till only the lye crystals remain. This lye can be used for various purposes.

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References
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lye

https://www.chemicalsafetyfacts.org/sodium-hydroxide/

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