Based on my personal research while making handmade bar soap. Learning both the physical and chemical properties of fats and oils.
Fats and Oils in Soap Making
- What is saponification
- Estimation of saponification of fats and oils
- Saturated fats
- Butters and additive fats
- Cocoa butter
- Shea butter
What Is Saponification?
Saponification is a type of chemical reaction between a strong alkali or base (such as sodium or potassium hydroxide) and a fat. Animal and vegetable fats and oils are made of ester molecules called triglycerides. An ester is a molecule that is formed from an alcohol and an acid. In the case of fats, glycerin is the alcohol, and the acids are fatty acids like stearic, oleic, and palmitic acids.
When the alkali solution is thoroughly mixed with the oils, a reaction called saponification begins. What this means is that the glyceride of the triglyceride breaks off to form glycerine and the sodium or potassium bond with the fatty acid to form soap. With sodium, you get bar soap; with potassium, you get liquid soap.
Every oil or fat has what is called a saponification number, which is determined by the amount of alkali needed to completely saponify the fat. This number is determined by titration a test sample with a standardized alkali and acid/base indicator.
Estimation of Saponification of Fats and Oils
Most people have heard about saturated fats and their link to obesity and heart disease and other ailments. But for soap, saturated fats have multiple benefit. Saturated fats are usually solid at room temperature and consist of straight-chained molecules.
For bar soap, they give the soap hardness as helping the soap last longer in the shower. Most commonly used saturated fat used for commercial soap making is beef fat, also known as tallow. It is usually the first and most abundant ingredient in many soaps. It is widely available as a by-product from the meat industry and is therefore one of the cheapest fats. It created a white and very hard bar of soap. Many people with sensitive skin have problems with soaps made with beef tallow. So, they usually use body washes or seek out bar soap made from gentler vegetable sources
Another common saturated fat is coconut oil. It also gives a very hard white bar of soap, but unlike tallow, the fatty acids are shorter length carbon chains that increase water solubility. This greater solubility in water helps generate more suds and increases the cleaning ability. Unfortunately, soap made from coconut oil alone would be drying to the skin so some conditioning and moisturizing ingredients need to be added. This drying of the skin is testament to the cleaning power of coconut fatty acid soaps. Alone they strip the skins natural oils right off. Another very common saturated fat is palm oil. It is the go-to replacement for beef tallow for truly vegan soaps. It is also a good fat when skin sensitivity to beef tallow is an issue. A common recipe for homemade vegan soap consist of palm, coconut, and olive oil.
Unsaturated Fats (Liquid Oils)
The best ingredients to balance the saturated fats in a soap recipe are the unsaturated fats. By contrast, these are usually vegetable oils that are liquid at room temperature and consist mainly of bent and branched chain molecules. They have the property of acting as emollients or moisturizers in soap recipes. In the right proportions, they can effectively offset the drying qualities of saturated fats and create a bar soap that is hard, white, sudsy, and conditioning as well. One of the best condition oils is olive oil. It consists mainly of oleic acid, but the conditioning action mostly comes from the unsaponifiable, which are organic ingredients in the oil that are not acted upon by the alkali. One of which is squalane, which is used in many high-end antiaging cremes. Some other common vegetable oils are soybean, corn oil, safflower oil, castor oil, and sunflower oil. It should be noted that some vegetable oils, notably the polyunsaturated ones, have a shelf life and will darken and go rancid with age.
Butters, Additive Oils, Fats
If a more luxurious soap is desired, you can add special kinds of butters and fast to soap. They add to the smoothness and skin-conditioning properties by leaving a protective barrier on the skin to help moisturize without feeling greasy. Some butters like cocoa butter even have mild pleasant aromas that can add to the bathing experience.
You might already be familiar with cocoa butter in moisturizing creams, cosmetics, and lip balms. It imparts a silky smoothness to personal care products and is an excellent emollient. It's also one of the most stable fats at least partly due to the antioxidants present. It has a typical shelf life of two to five years.
Cocoa butter is extracted from the cocoa bean in tropical regions. It consists of roughly 60% saturated fats and 40% unsaturated fats. It is an offwhite to cream-colored solid which have a melting range of 93 to 101 degrees Fahrenheit, which is near body temperature. But, cocoa butter is stable and quite solid at room temperature. This makes cocoa butter perfect for its most common use of all: the manufacturing of chocolate products. All chocolates are made with cocoa butter including milk chocolate, white chocolate, and dark chocolate.
Shea butter is a buttery fat extracted from the African shea nut. It is a cream-colored fat this is softer than cocoa butter and does not have as much saturated fat. In its native land of Africa, it is used in food preparation. In fact, it is sometimes combined with other fats to substitute for the more expensive cocoa butter in chocolates. But the taste is different so 100% cocoa butter is the preferred fat for chocolate manufacture.
Shea butter also has the property of containing nonsaponifiable components. What this means is shea butter has ingredients that will not chemically interact with alkalies to form soaps. This gives shea butter its texture and emollient capabilities. The main fatty acids are the saturated stearic acid and the unsaturated oleic acid.
Questions & Answers
Question: Where do fats and oils used in soap making come from?
Answer: Oils are vegetable sourced glycerine esters. Examples are olive, palm, and corn oil. Fats usually refer to glyceride esters found in animal “fat” which is normally a byproduct of various meat industries. Animals fats would be lard from pork and tallow fat from cows.
Question: What is the main difference between soaps made from animal fats and plant oils?
Answer: Animal fats typically create a harder bar of soap that may or may not be beneficial to your skin. Vegetable oils produce soap that is generally softer and gentler to the skin. There are exemptions of course. Coconut and Palm Kernel Oils produce soap that is hard and can be drying to the skin. These oils are made of short chain saturated fats that make excellent sudsy cleansing soap. So much so as they strip the skins natural oils. Therefore, most soap recipes don’t have more than 30% coconut or palm kernel oils.
Question: The saponification reaction occurs between an acid and base, shown in the figure in the procedure. In the reaction performed what is the acid and base?
Answer: The “acid” is fatty acid from the oil. It is liberated from the glycerin Ester by the base in saponification. The base is a strong alkali like sodium hydroxide or potassium hydroxide. The saponification byproduct is glycerin from the oil. For soap making, glycerin is not removed from the soap mixture.
Question: How can I find a chart that not only lists the benefit of soaping oils, but also skin conditions that are improved by certain ingredients? For example, Eczema is improved by using _____oils in CP soap or Extreme dry skin is improved by using _____oils in CP soap.... and so on.
Answer: I am not sure on the Eczema aspect but dry skin can be assisted by adding Shea butter or jojoba oils to soap recipe. Also, adding an additional amount of vegetable glycerin would act as an emollient and help trap moisture in.
Question: There are many "blended" oils on grocery shelves now. Is there an SAP value for blended oils? Ex: 80/20% sunflower & virgin olive oil. Could blended oils be used for soap?
Answer: Yes, you can. For example, you can take the 80/20% sunflower & virgin olive oil measure a mass, and use percentage to calculate the masses of each oil. Look up SAP values for each oil and add them together to get the amount of sodium hydroxide or potassium hydroxide required for saponification.
Jason (author) from Indianapolis, IN. USA on August 13, 2020:
It helps when you are actually interested in what your writing about.
Jenny on August 12, 2020:
Great post. Most posts out there tell you what is good for what, but not why. If I know why, then I can target certain qualities easier. Very informative, thanks.
Jason (author) from Indianapolis, IN. USA on October 30, 2019:
Your quite welcome
Norma Rios Ortiz on October 30, 2019:
Thank you for all the .
Concerned soap lover on May 14, 2019:
What are soaps that are used in production of commercially available soaps?
Jason (author) from Indianapolis, IN. USA on May 13, 2018:
Animal and vegetable fats and oils contain fatty acids usually bonded to glycerin. That’s why you hear about triglycerides and fat. Soaps are metal salts of the fatty acids. Sodium is cheap and produces the hardest soap. Sodium hydroxide is a strong base and is needed to sever the bonds of the fatty acids with glycerin. With thorough mixing and the heat of reaction, the sodium hydroxide turns the melted fats into soap. The glycerin is left in as a byproduct as an emollient.
Apu saha on May 07, 2018:
why we use oil or fat in soap making process..??
can anyone give me answer please..?
David on August 19, 2017:
This article was very helpful..am a chemistry undergraduate student currently carrying out a seminar title "the role of different fats and oils in soap making" please can you share me more information which might help
Jason (author) from Indianapolis, IN. USA on January 21, 2017:
Although you could gather some info from soap making forums, I would recommend you actually go to the library and get books on soap making. Pretty in depth information. I will try to source literature soon and post it on this article.
Sév on January 21, 2017:
Hello ! Is it possible to have the links to where you found also this infos ? It would be terribly nice :)
Hello on October 30, 2014:
This is an amazing post
Rachel Koski Nielsen from Pennsylvania, now farming in Minnesota on July 19, 2012:
This is a great hub! Very informative.
Anjili from planet earth, a humanoid on April 11, 2012:
The making of soap was one of mankind's greatest discoveries in our attempt to remain clean. The art has always intrigued me. My wife has always made liquid soap which is very handy in times of need. I should urge her to try making the solid type. Good share. Voted up
Jason (author) from Indianapolis, IN. USA on April 02, 2012:
Oh thank you. I do recommend you try to make some. The best oil in my opinion is olive oil.
Healing Herbalist from The Hamlet of Effingham on April 01, 2012:
Saponification! Love that word. Thanks for the great information. I have always wanted to make soaps, but never got around to it. Up, and useful