Is Lye Safe? Lye in Soap Making: Safety, Process & Applications

Is the Lye Safe?
Is Lye Safe? Lye in Soap Making: Safety, Process & Applications 7

When I first started learning about making soap, way before Mayan Magic Soaps, I was surprised to find out you NEED the lye to make soap. I knew lye could be dangerous, but that’s about the extent of my knowledge on sodium hydroxide. So I went digging, checked out some books from the library. I’m definitely not an expert, but I can help you understand lye a good bit more by the end of this article. Quick version: Lye is caustic and dangerous if not handled properly. It will burn your skin. The vapors that it gives off when mixing with water can hurt or kill you. Do not breath them in! Make sure to wear protection when handling lye, and keep a bottle of white vinegar to neutralize the chemical burn if it gets on your skin. With that said, lye is perfectly safe to work with.

For example: all the lye in soap is used up in the saponification process. There isn’t any caustic substances left after saponification. That’s the short answer. If you’d like to learn more as I did, we will dive into the more complex details below.

Lye to Make Soap

Lye to Make Soap
Is Lye Safe? Lye in Soap Making: Safety, Process & Applications 8

Origins of Lye: From Natural Sources to Modern Synthesis

Origins of Lye: From Natural Sources to Modern Synthesis
Close-up image of woman putting spoon of lye in plastic jar when making soap at home

Lye is an alkaline compound made from either local material or sophisticated metals; used in making soap and other products. The homemade lye is made from pure and harmless ingredients that quickly dissolve in water referred to leaching ash. The key elements are wood ash and water. The modern lye is made through a process of membrane cell chloralkali by dissolving salt in water and heating it to form crystals. The compounds lye can be made in the form of pellets, flakes and microbeads in addition to solutions for various purposes.

The lye made from metals hydroxides is an essential compound and very caustic with a capability of causing skin burn, blindness when safety precaution not observed during handling. Despite its caustic nature, there is a frequent interaction of lye made products with humans daily under different forms. This interaction has proved that lye is non-caustic due to its vast processing and crystallization to remove harmful impurities (Eschliman, 2015).

Lye’s Versatile Applications: Beyond Soap Making

The lye is generally used in the manufacturing and processing of many items including food preservatives, making soap, production of biodiesel, unclogging of drainages and detergents among other products. On food processing, the lye is used as a tenderizer for various types of food and to cure certain types of food as well, such as in olives making it less harmful.

Lye can also be used in the household for cleaning and removing grease on surfaces. Sodium hydroxide also used in the tissue digestion, most often the decomposition of the carcass is the widespread application of its use. It noted an increase in water content and temperature highly increases the process of action of lye. It’s the most effective method due to its large scale availability and cheap coast of obtaining. The use of lye is also employed in fungi identification as it helps to provide colour change to the specific species for easy identification. (Ferreira, 2016).

Lye is often made from ordinary table salt consumed by humans. The salt is dissolved in water and electricity is introduced in the solution by electrodes, thus creating a chloride, hydrogen and lye product. Lye used in making soap, and any hair cleaning products contain sodium hydroxide and potassium hydroxide. The detergents made from potassium hydroxide dissolve quickly in water and are soft as opposed to their counterparts containing sodium hydroxide. Several procedures have been done to add the content of lye on the product to make it soap (Lew, 2009).

The Chemistry of Soap: Saponification and Its Key Ingredients

The Chemistry of Soap: Saponification and Its Key Ingredients
Is Lye Safe? Lye in Soap Making: Safety, Process & Applications 9

The chemical process involved in the manufacturing of soap is referred to as saponification. The solvent can be either handmade or commercially manufactured in which all the process require the use of lye. The key ingredients in the making soap are either; saponified oil, sodium cocoate, sodium palmate, sodium tallowate and sodium olivate, among others. The combination is mixtures of other compounds with sodium hydroxide to form soap. Fats and oils undergo hydrolysis to yield glycerol and crude soap.

Saponification is the chemical reaction involved in the conversion of fats to soap and alcohol; it entails an interaction between an acid and a base to form a salt in the presence of heat. In the manufacturing of soap, the sodium hydroxide is the base while fatty acids are acids that combine to form triglycerides often found in oils. The combination of specific oil with sodium hydroxide and liquid lye creates a chemical reaction that leads to the formation of soap, often called saponification.

In the industrial preparation of soap, tallow a fat obtained from animals or vegetable heated in combination with sodium hydroxide during saponification and latter precipitated with sodium chloride to form soap. The water layer often removed on the top of the mixture and the glycerol obtained by use of vacuum distillation. The process is essential as it aids in the interaction of the compounds and gives the soap its cleansing ability. Crude soap obtained by saponification always contain impurities of sodium chloride, sodium hydroxide and glycerol.

The impurities are removed by boiling crude soap in water and re precipitating with salts and is repeated severally to ensure complete removal of harmful contaminants. The amount of lye required in the manufacturing of different soaps differs depending on the type of fatty acids. It is crucial to observe the exact ratio during preparation to prevent excess impurities that may fail to precipitate, causing harm to the skin (Meher, Sagar, & Naik, 2006).

The homemade preparation of soap can be done using already pre- saponified lye. The lye has been processed and is less harmful to human skin to avoid direct handling of the product. Lye has been in use for centuries in making soap, and correctly handling of lye in accurate proportion to reduce the risk of skin damages in making soap. Lye used in manufactured soap is converted to a harmless product through the reaction of oils and butter, in addition to creating the scent and other properties such as vitamins and minerals to the soap.

Ensuring Safety and Quality: The Role of Lye in Product Manufacturing

Ensuring Safety and Quality: The Role of Lye in Product Manufacturing
Is Lye Safe? Lye in Soap Making: Safety, Process & Applications 10

Saponification ensures all lye products are used up in the process; this ensures the safety of the product since no trace of the lye compound is found on the final soap product. Lye allows the mixing of oils with liquids unnatural phenomena, to reduce the effect of lye, it’s added to water first and not the reverse. During saponification, lye is converted into another compound hence losing its caustic properties or making it absent in the soap as in the initial state.

The lye often found in liquid and beads used in the saponification process and latter cured in weeks to reduce the harmful effects ensuring a 100% complete chemical process (Zhu, Chambers, & Naik, 2000).

The saponification process is programmed to produce different types of soaps, the hard and soft soap depending on the lye used — hard soap made from sodium hydroxide essential for cleaning in hard water containing chloride ion and magnesium ions. The soft soap is made from potassium hydroxide rather than the sodium hydroxide (Prieto Vidal et al., 2018).

Conclusion: Balancing Lye’s Benefits and Risks in Everyday Products

Conclusion: Balancing Lye's Benefits and Risks in Everyday Products
Is Lye Safe? Lye in Soap Making: Safety, Process & Applications 11

In conclusion, the lye used to make daily consumed, and used products might be made less caustic by saponification. Besides, to other methods to reduce the dangerous impurities from the product formed. It is challenging to produce other products in the absence of sodium hydroxide; thus, care and safety observed in handling with the lye to prevent unnecessary accidents.


Eschliman, D. (2015). Ingredients: A Visual Exploration of 75 Additives & 25 Food Products. Simon and Schuster.
Ferreira, A. R. F. (2016). Body disposal in Portugal: Current practices and potential adoption of alkaline hydrolysis and natural burial as sustainable alternatives.
Lew, K. (2009). Acids and Bases. Infobase Publishing.
Meher, L. C., Sagar, D. V., & Naik, S. N. (2006). Technical aspects of biodiesel production by transesterification—a review. Renewable and sustainable energy reviews, 10(3), 248-268.
Zhu, S., Chambers, J. G., & Naik, V. (2000). Soap. Kirk‐Othmer Encyclopedia of Chemical Technology.
Prieto Vidal, N., Adeseun Adigun, O., Pham, T., Mumtaz, A., Manful, C., Callahan, G., … & Thomas, R. (2018). The Effects of Cold Saponification on the Unsaponified Fatty Acid Composition and Sensory Perception of Commercial Natural Herbal Soaps. Molecules, 23(9), 2356.

Thank you so much for reading our article on lye. Hope we cleared some things up for you. You can check out all of our DIY Supplies for soap. You can find all of our blogs here.

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