There are few things in this world that are as refreshing as a bubble bath with fragrant soap. We wash our hands with soap after a long, hard day or before eating because we believe that the action of soap cleans them. Soap is a cure-all for different kinds of dirt: water-based paints, oil-based paints, mud, grease, the list goes on and on. How does soap help with such a wide range of targets? How did humans discover its immense potential as a cleaning agent?
The word “soap” originates from the Proto-Indo-European language to denote “dripping” or “trickling”. This language was developed during the Neolithic age between 4500-2500 BC. “Soap” is also related to the Latin word “sebum” which refers to fat or grease, which is an accurate description of the nature of soap. Soap is made from fats or oils by the process of saponification. In this process, the triglycerides are combined with a strong base to produce glycerol and fatty acid salts. The resulting salt is called soap. The glycerol is usually kept incorporated within the soap as a softening agent.
How does this formulation of soap help rid the body surface of dirt? Most of the grime on the skin surface is infused with oil, which is secreted from the sebaceous glands in the skin. The oil is hard to wash off with water because the water molecules are hydrophilic i.e. they are more attracted to each other than to the oil, which is hydrophobic. However, soap can mix with both oil and water because it shares qualities of each- the base gives it hydrophilic head and the fatty acid component gives it a hydrophobic tail.
The earliest records on soap date back to Babylon in 2800 BC. The formula for soap was found on a clay tablet from 2200 BC and included water, alkali (a base that dissolves in water), and cassia oil. Ancient Egyptians also used soap, which combined animal and vegetable oils with alkaline soils, as evidenced by papyrus records from 1550 BC. In Ancient China, soap-like materials were synthesized from a mixture of pig pancreas and plant ash to produce bathing beans. The earliest mention of soap by its Latin name sapo appeared in 77-79 AD in the book Historia Naturalis by Pliny the Elder, a Roman author and naturalist. The book described the synthesis of soap from tallow, a rendered form of mutton fat, and ashes. Pliny mentioned it as a pomade to style hair and commented that the Gaul and German men were more likely to use it compared to the women. The Romans differed in their method of cleaning the body- they would massage the oil into the skin and subsequently scrape off the oil, and the accompanying dirt, with a strigil.
In medieval Europe, soap making had reached its zenith between the 8th and 9th centuries, being well known in Italy and Spain. However, since this soap was made from animal fat, it had a very unpleasant smell. The art of adding a pleasant smell to hard soap was invented in the Middle East during the 8th to 13th centuries, also known as the Islamic Golden Age. Soaps were infused with rosemary and lavender and the famous Aleppo soap incorporated laurel oil, which is known for its spicy and sweet scent. By the end of the 13th century, the manufacture of soap had become industrialized with centers in Nablus, Aleppo, Fes, and Damascus.
The use of soap, however, did not become mainstream till the 18th century. Soap was popularized by advertising campaigns in Europe and America, which emphasized the relationship between health and cleanliness. This was because it had become apparent that hygiene played an important role in reducing the instances of disease. Therefore, it became necessary to produce soap on an industrial scale. The problem was that there was no good way to obtain the base that was required to make soap. Previous chemists were dependent on burning kelp or wood and using the ash produced as a source of base. The process resulted in a very low yield and so it was imperative to establish a large-scale synthesis procedure. To this end, in 1780 James Keir, a Scottish chemist, developed a method of extraction which involved slowly passing dilute solutions of sulphates of potash (K2CO3) or soda (NaHCO3), which were also present in ash, through a thick paste of lime (Ca(OH)2). This method was more viable because lime was readily available in large amounts from limestone.
Armed with this knowledge, Keir set up a manufacturing unit for the synthesis of base and to this unit he later added a soap manufactory. The next advancement came in 1807 when Andrew Pears invented transparent soap by removing the impurities present in soap. His invention was to benefit the upper classes in London whose delicate complexions needed finer soap as opposed to the working class whose tanned complexions could make do with crude soap.
There are other noteworthy improvements in the field of soap-making, which included packaging soap into useable portions. In 1837, Robert Hudson, an English businessman, developed soap powder by grinding the soap with a mortar and pestle. His advertising campaign convinced his customers that this product was essential. Furthermore, they could avoid the tiresome labor involved in cutting off soap flakes from the large blocks of soap that were available in the market. However, Hudson never manufactured his own soap, instead, he would purchase the raw soap from William Gossage, an English chemical manufacturer, who optimized the synthesis of cheap, good-quality soap. To do so, he incorporated sodium silicate, which was readily available, into soaps. An additional advantage was that sodium silicate could soften hard water by removing the calcium ions, thereby preventing the deposition of minerals such as calcium carbonate on surfaces. Sodium silicate is now routinely used in the manufacture of commercial detergents. He also added pigments to the soap, resulting in the manufacture of blue mottled soap, which became world-famous at the time. The soap even won a medal for “excellence in quality” at the International Exhibition in 1862. Eventually, the company became a part of the Unilever group that was founded in 1886.
The most predominant form of soap these days, liquid soap, was created in the 19th century. In 1865, William Sheppard from New York patented a liquid version of soap. He had discovered that by dissolving a small amount of soap with a solution of aqueous ammonia he could produce thick, liquid soap. The ammonia acted as a base and reacted with oils to form soap. The water in the soap made it easy to clean. Another liquid soap, which went on to be more famous, was developed in 1898 by B.J. Johnson, which was made by combining palm oil and olive oil. The resultant soap became so popular that the company was renamed after the soap- “Palmolive”.
On a personal note, while researching this article I learned a lot about soap making. It was intriguing to see how the ingredients for homemade soap: coconut, sweet almond, rice bran, and all the oils that can possibly be named, are used; making it sound more like a Sunday brunch recipe. I’ve also always been fascinated by the incorporation of flowers, fruit peels, leaves into soap (reminds one of a hiking trail, does it not?). It was fascinating to see how soap evolved from being a luxury item to a necessity and now to pieces of art.
Author:
Ananya Sen is currently a Ph.D. student in Microbiology at the University of Illinois at Urbana-Champaign. When she’s not studying oxidative stress, she is busy pursuing her passion for scientific writing. Currently, she contributes articles to ASM, ScienceSeeker, and her own blog where she discusses the history of various scientific processes. She is an ardent reader and will happily discuss anything from Jane Austen to Gillian Flynn. Her graduation goals include covering all the national parks in the U.S. with her sidekick Oscar, a Schnauzer/Pomeranian mix.
Illustrator:
Arghya Manna is a comics artist, illustrator, and a Ph.D. dropout. He began his career as a doctoral student at Bose Institute, India. He had been working on Tumor Cell migration in a 3D environment. Along with this, he was an active participant in several projects related to tumor immunology and cancer stem cell. After leaving the lab without bagging the degree Arghya found refuge in art and got involved in drawing comics. He is an enthusiast in History of Science and has been running a blog named “Drawing History of Science”. Arghya wishes to engage the readers of history and science with the amalgamation of images and texts.
Editor:
Roopsha Sengupta is the Editor-in-Chief at ClubSciWri. She did her Ph.D. at the Institute of Molecular Pathology, Vienna and postdoctoral research at the Gurdon Institute, University of Cambridge, UK, specializing in the field of Epigenetics. During her research, she was involved in many exciting discoveries and had the privilege of working and collaborating with a number of inspiring scientists. As an editor for ClubSciWri, she loves working on a wide range of topics and presenting articles coherently, while nudging authors to give their best.
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