Don’t put any of that lye in my soap!

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Some people, who know that I make natural soap, will say something like ‘it is so great that you don’t use lye (sodium hydroxide) in your soap’…sorry what was that, I ask. They will reply with something like ‘well you know, you make natural soap, everything is natural, there are no chemicals inside and so there can’t be any lye inside’. Well, I hate to tell you this but everything that exists in this world is chemical in its most basic sense. In this blog I would like to tell you that BECAUSE I make natural soap it does and indeed must include lye, but actually there is no lye in the cured soap.

So maybe we should start by looking at what lye (its chemical name is Sodium Hydroxide) actually is. Sodium hydroxide is a base or an akali. We combine this alkali with different oils that we are using to make the soap. The alkali (sodium hydroxide and water, which is otherwise known as lye solution) and the fatty acids of the oils then combine in the reaction of saponification which produces soap + glycerin. Some companies will take the glycerine out of the soap and sell that as a by-product. However, real handmade soap leaves the glycerine in the soap as it makes for a very moisturising soap.

In the past, ashes would be percolated with water which produced a lye solution. Ancient cultures, such as Babylon and Egypt would combine this solution with fat to make soap to clean clothes. It is presumed that this was an accidental discovery with the fat from sacrificed animals mixing with ashes from fires being rained upon and probably producing a foaming substance. Apparently, they found that this helped to clean things and thus started actually making soap. This is first recorded in Babylon in 2800BC. In the past, soap was made from this ash solution. In the Middle East, limestone (calcium carbonate), known in solution as soda wash or soda lime, was cooked up with oil or fat and then rinsed many times with salt water to remove the soda wash and then at the end rinsed with pure water. This is a long tedious process, taking at least 10 days. It is the process apparently still used in the production of traditional Marseilles soap.

However, no longer is lye made from ashes, it is unreliable and very time consuming. Nowadays, lye is made industrially with the electrolysis of salt water. It may frighten many people to know this but sodium hydroxide has many uses commercially. It is used in food production, water purification, paper production and in the cleansing process of fruit and vegetables. As an ingredient, it can be found in household cleaning substances, drain cleaners and detergents. It can also be used in food processing with olives and corn. According to one source, it is written that consumers will come into contact with food that has had sodium hydroxide used in the processing of that food in some way ‘several times each day’ ( It is apparently used in the processing of many foods, including chocolate, drinks and icecream. Interestingly, pretzels are even coated in it and then baked so as to be chewy.

The chemical, in its pure form, is highly corrosive and caustic (which is why it is often referred to with the name ‘caustic’. It must be handled with great care, especially in regard to the eyes, the respiratory system and the skin. It can burn. When handling sodium hydroxide, one should wear gloves and eye protection. However, sodium hydroxide as it is used in modern handmade soap (and presumably food), does not appear in the soap that you buy and use. It is only a catalyst in the soapmaking (saponification) process. The amount of lye which is used is dependent on the oils being used. This is then normally discounted by 5-10% (which means that there is less sodium hydroxide used than the saponification values of those actual oils) to make a mild, non-irritating and even moisturising soap. The oils and lye solution are mixed together, as the lye allows the water and oil to mix, which of course can’t normally happen. This mixture is then poured into the mold, left to heat up and harden. After a day or a few (depending on the oils being used), the soap is then taken from the mold. At this stage, the saponification process has finished, but the soap is still left to cure for 4-6 weeks so that excess water can evaporate and the bar can harden. After this period, there really only is saponified oil and water left.

How is it listed on labels?

Some labels might list it as sodium hydroxide or lye. Most labels will list it as an oil starting with ‘sodium’, for example: sodium olivate or sodium palmate. If your soap doesn’t have sodium hydroxide in some form listed on the label, then it will have much less mild synthetic chemicals, being detergents, in there. Somehow, the product has to get your skin clean. Adding sodium hydroxide to soap is the same as the tradition of leaching ashes, it is just quicker for the soap maker. The sodium hydroxide allows oil and water to mix so that the oily part of the soap can pick up oil and dirt and then the water part of the soap can allow the water which is washing over you to pick up that dirt and oil and wash it away. There is no trace of sodium hydroxide left at all in a well made handmade natural soap.

If you would like to join the soapmaking class on November 29th in Kalamiş, please email Jo on


Royal Society of Chemistry

Marius Fabre


Colonial soapmaking

#handmadesoap #lye #saponification #sodiumhydroxide #soapmakingworkshop

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