Chemistry of Soap Making

Understanding the chemistry of soap making will help you better understand the process that goes on when you make soap. It will help you develop a true skill for your craft and turn you in an expert soap maker, able to create your won soap recipes with your own measurements.

Historical Chemistry

To make soap, you need to mix animal fats or oil with an alkaline solution. From reading the history of soap, you know that it is a mixture of animal fats or oils with ash. In this simple description, it is the ash that contains an alkaline solution which helps create the soap.

Throughout the course of soap making history, however, scientists and inventors sought to improve the conditions and materials which were used to make soap. The first breakthrough came in 1791, when Nicholas LeBlanc discovered a way to make sodium carbonate (an alkaline solution) from simple table salt. This method was able to yield good quality soda ash in large quantities. As a result, ash from fireplaces were no longer used to make soaps, and soap could be produced on a larger scale.

Next came Ernest Solvay, a chemist who invented the ammonia process. This reduced the cost of making soda ash, as well as greatly increased the quantities that could be produced. Other chemists, such as Michel Eugene Chevreul, who discovered the chemical nature and relationship of fats, glycerine, and fatty acids, also contributed scientific research to the chemistry of soap making.

The chemistry of soap making remained the same until 1916 during the time of World War I in Germany. There was a shortage of fats for soap making in the country, and the scientists had to find a way to synthesize non-soap washing and cleansing products in order to form raw materials to make their soap. These synthetic detergents, as they were called at the time, were found to be very effective at cleansing. Plus, they had the added bonus of not combining with the mineral salts often found in water, making it longer lasting.

Modern Chemistry

Modern soap is made up of the sodium or potassium salts of fatty acids, you may know these by the names 'crude soap' or 'glycerol.' To create this soap, a soap maker has to make oils or animal fat react with an alkaline solution known as lye or caustic soda. An alkaline solution is used because alkaline solutions are bases (as opposed to acids) and have the ability to corrode. When the fats and lye combine, a process called 'saponification' takes place.

In the process of saponification the fats in the mixture are hydrolyzed, meaning hydrogen atoms are released from the bonds that hold them together to water molecules. Specifically, the alkali (in this case lye) splits the molecules of fats or oils into two major parts known as glycerin and fatty acids. Next, the sodium or potassium components of the alkaline solution (lye) join with the fatty acids. The combination of sodium or potassium with the fatty acids creates the end product we know of as soap.

Because of this process, soaps have the ability to dissolve in water, but at the same time to dissolve grease or oils and help the water carry this away. It is this property of soap that gives it the ability to clean. A simpler way of seeing it is that soap has the ability to bridge the gap between oil and water, allowing them to mix and therefore able to wash away.

Given this knowledge, you can experiment making your own soap recipes. You simply have to keep in mind how much lye you should match with certain amounts of animal fats or oils, and what combinations will yield different types of soap. Good luck!