Stearic Acid: It's Everywhere!

Have you ever wondered what shampoo, candles, detergents, and hard candies have in common? I know you are all probably wracking your brains trying to think of something. However, the similarity cannot be seen, since it is buried deep within the terrifying ingredient panels on all of these things….

Harvested from the fat of animals and many plant oils (1), stearic acid is the common tie between all of the above products. This is a chemical that is useful for several reasons (2):

·      Hardener: makes soaps, candies and candles solid

·      Surfactant: separates dirt from skin/clothes so water can wash the dirt away in detergents

·      Emulsifying agent: makes oil and water stick together in shampoos and other personal care products

Stearic acid is a long chain of connected atoms. One side of the chain likes water, while the other side of the chain doesn’t like water. This side likes dirt and oil. Having two different sides makes stearic acid an amphipathic chemical, which helps it to act as a temporary bridge between oil and water, allowing it to clean clothes, skin, and other things (3). Be careful though, because it could also cause bathtub rings (4).

This rad two-sided chain isn’t easy to make from animal fat and plant oils. First you have to split up the fat/oil, which is made of 3 long chains held together by a smaller chain called glycerol. This is called saponification (5). Then you have to separate the long chains from the smaller chains in the purification step (5).  

For those of you with a sweet tooth, your grandma wasn’t lying to you when she said, “don’t eat too many hard candies.” Even though stearic acid is only slightly harmful to our bodies, it can still be damaging if swallowed or inhaled in very large amounts (6). It can cause you to turn red and splotchy, and sometimes even puffy (6). If you want to avoid this possibility you can always use soybean products or beeswax instead (7).

Now you have the scoop on all things stearic acid! 

 

 Candles containing stearic acid

 

References: 

(1) Natural Substitutes for Stearic Acid. eHow. http://www.ehow.com/info_8718549_natural-substitutes-stearic-acid.html (accessed March 5, 2017).

(2) How does stearic acid work in skin cleansers? How Stuff Works Health. http://health.howstuffworks.com/skin-care/cleansing/products/stearic-acid-in-skin-cleansers.htm (accessed March 5, 2017).

(3) Stearic Acid and Sodium Stearate. http://www.ch.ic.ac.uk/rzepa/mim/domestic/html/stearic_acid.htm (accessed March 5, 2017).

(4) Stearic Acid. http://science.jrank.org/pages/6482/Stearic-Acid.html (accessed March 5, 2017).

(5) Fatty Acids. In Ullmann's Encyclopedia of Industrial Chemistry [Online]; Wiley-VCH Verlag GmbH & Co. KGaA. Posted December 15, 2006. http://library.mtroyal.ca:2059/doi/10.1002/14356007.a10_245.pub2/full (accessed March 5, 2017).

(6) US National Library of Medicine, Stearic Acid. TOXNET Toxicology Data Network. https://toxnet.nlm.nih.gov/cgi-bin/sis/search2/f?./temp/~kam6CZ:3 (accessed March 5, 2017).

(7) Natural Substitutes for Stearic Acid. eHow. http://www.ehow.com/info_8718549_natural-substitutes-stearic-acid.html (accessed March 5, 2017).