Local Girl Scouts visited a chemistry lab on the Northwestern State University campus to learn about the chemistry of soapmaking and to make their own soap. Carol Chin (joint faculty at NCPTT and NSU), Christina Palomo (NSU biology major) and Debbie Smith (NCPTT Chief of Historic Landscapes) served as instructors for 10 fourth and fifth grade girls, members of the Girl Scouts of Louisiana Pines to the Gulf Council Troop 1512.
The girls were provided with a little background on the old ways of soapmaking. Traditionally, lye (sodium hydroxide) was extracted from wood ash. The pH of lye is very high because lye is a strong base, so the girls tested some lye prepared from wood ash and found the pH to be approximately 12. The instructors also talked about how triglycerides, fats, are converted to soap and a byproduct, glycerol.
The girls worked at individual lab stations, measured the ingredients, and prepared their soap using the hot process saponification method. They heated shortening, lye, and alcohol in a beaker using a hotplate, stirring the mixture using a magnetic stirring bar as well as a glass stirring rod. After much stirring and heating, the mixture began to thicken and form soap.
Next the girls added flower petals, oatmeal, or tea to personalize their soap, and then “purified” the soap by adding a saturated salt solution. The salt solution caused the soap to separate from the glycerol byproduct. This step also helped to eliminate any excess lye. They poured off the byproduct, rinsed their soap chunks, and took their freshly made soap home to re-melt and pour into molds.
Soap is a household item that we often take for granted, but the girls learned that the task of soapmaking was historically a time-consuming endeavor that was necessary in order to have soap for cleaning, washing, and bathing.
“I liked that we got to learn the formula before we made the soap,” said Girl Scout Lauren Mathews. “I am going to give my soap as a present, so I haven’t used it, yet. I really liked working in the chemistry lab!”