The Real about Sodium Hydroxide aka Lye

The Real about Sodium Hydroxide aka Lye

October 31, 2016


Amongst the many scientific names of chemicals on commercial soap labels it's hard to notice sodium hydroxide as an ingredient. When reading the few ingredients on handmade soap, it's easy to spot. Handmade soap usually advertises their use of natural ingredients, but there is always the question of what is sodium hydroxide and is it necessary in soap? So let's dig deeper into the use of sodium hydroxide in soap.

What is sodium hydroxide?

Sodium hydroxide is a caustic soda that when combined with animal fat or vegetable oil, processes into soap. This process is called saponification. Lye is necessary to make bar soap, just as potassium hydroxide is needed for liquid soap. Essentially, soap is a mixture of base oils, a diluted lye solution, and herbal additives.


During the soap making process the lye is heavily diluted with water, and added to the oils to create a thick mixture. The mixture is then added to a mold for 24 hours to harden, and set to cure for 4-6 weeks. During the curing process, the soap bars lose water weight, in which the sodium hydroxide is dissolved. Therefore lye is needed for the chemical process that soap goes through, but it's not present in the final product.

Soap Nostalgia 

Many of our parents & grandparents are very familiar with lye soap. It's what they remember as a harsh soap often mixed with animal fat. Back then the soap was harsh, but today we don't experience that due to advances in the curing process. Lye has been recorded and depicted in the transcripts of many ancient societies such as the Mesopotamia and Egypt.  In modern times, soap makers generally use a synthetic sodium hydroxide discovered by Humphrey Day. The discovery of this alkali, made it easier and feasible for soap makers to enhance the traditional practice of making lye.

Take Precaution when dealing directly

When dealing with lye it is very important to take the proper precautions, as it is very caustic and can irritate the skin directly. When making soap, I have to use goggles and gloves. I've gotten lye on my skin and in my eyes and it's not a good feeling whatsoever. If if comes in contact with the skin use an acid like vinegar to neutralize, and water for the eyes.

The Misconception

Sodium hydroxide is actually used in a lot of products from cosmetics, cleaning, and even food. Even in a concentrated effort to avoid lye, it's nearly impossible. The real about sodium hydroxide is that you can't make soap without it, and that's just not the case if you're making it from scratch. There is a melt and pour method if you personally don't want to deal with lye, but the soap base you melt down has been made with it. Thankfully sodium hydroxide is only a small piece within all of the other natural ingredients used. The soap that you use  from Herb'N Eden has been through a curing process, where the lye is no longer present in the finished product. It's better than an ingredient list full of chemicals you can't pronounce and that strip the skin of it's natural oils.

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