← Everything Everywhere Daily: History, Science, Geography & More
Everything Everywhere Daily: History, Science, Geography & More
A History of Soap and Detergent
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Sometime in the last 24 hours, most of you have used soap or detergent, either directly or indirectly. Soap, like many things, was most likely discovered by accident thousands of years ago. But fast forward to today and these products are used for cleaning almost everything from our bodies to cars to dishes, soaps and detergents, despite being similar products that serve similar purposes, approach their tasks slightly differently and are used in different circumstances. Learn more about soap and detergent, how they were developed, and how they work on this episode of Everything Everywhere Daily. This episode is sponsored by Fiji Water. You've probably heard of Fiji Water and have seen it in stores. Well, Fiji Water really is from the islands of Fiji. Drop by drop, Fiji Water is filtered through volcanic rock 1600 miles away from the nearest continent. In all its pollution protected and preserved naturally from external elements. 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Soap and detergent are so ubiquitous in the world that we rarely even think about them. They're used for cleaning and hygiene, and most of us may have never even gone more than a few days without ever using them. Yet there was a time when people spent their entire lives without using soap. We don't have any details as to when humans first discovered or invented soap, but it was likely an accidental discovery that occurred thousands of years ago. It wasn't soap exactly as we would think of it today, but it would have been soap like it probably happened when melted animal fat was mixed with wood ash from a campfire and then mixed with water. I'll get into the chemistry involved in just a bit. But that sample mixture had the components required to create a soap like substance. The earliest actual evidence we can point to of a soapy substance comes from ancient Babylon around the year 2800 B.C. where archaeologists found clay cylinders containing soap like mixtures of of fat and ash. However, this wasn't quite soap as we know it. It was likely used more for cleaning wool and cotton textile production rather than personal hygiene. The ancient Egyptians developed their own cleaning methods around 1500 BC, mixing animal and vegetable oils with alkaline salts. They understood that cleanliness was connected to health and religious purity, which drove the innovation in cleaning methods. Meanwhile, the Romans were experimenting with a substance that they called sapo, which gives us our modern word for soap. According to the legend, this was discovered when fat from sacrificial animals mixed with wood ash on Mount Sapo, which created a substance that made washing clothes easier in the river below Mount Sapo probably didn't actually exist. But the story of accidentally discovering that the mixture of fat and ash clean clothes might have a bit of truth to it. And it was probably something that was discovered independently multiple times around the world. These ancient people were unknowingly performing a chemical reaction called saponification. When fats which contain fatty acids, combined with strong alkalis, such as those found in wood ash or other sources, they form soap molecules that have a unique structure. Alkalis are just a type of base which is the opposite of an acid. The alkalis used in early soap came from potassium, sodium or calcium hydroxide. This is what the ash brought to the mixture with the fats. One end of the soap molecule loves water, which is called hydrophilic, while the other end hates water and is called hydrophobic. The hydrophobic end of the molecule readily attaches to oils, grease and dirt that are not soluble in water because it it's not water in a pool of water. When soap is added to dirty, oily surfaces and then agitated in water, the hydrophobic end of many soap molecules latch onto the grease particles, while the hydrophilic end sticks out into the surrounding water. As this happens, the soap molecules surround the bits of oil or grime in the form of tiny spheres called micelles. Inside a micelle, the grease is trapped at the center, protected from the water by the soap molecules. Because the outside of each micelle is hydrophilic, the whole structure can now be suspended and rinsed away in water. Soap allows oil and water to mix to form an emulsion. In addition to emulsifying oils, soap also lowers the surface tension of water, allowing it to spread and penetrate more easily into fabrics, skin, or surfaces, which helps lift dirt away. The combination of emulsification and reduced surface tension explains why rinsing with plain water isn't as effective as washing with soap. During the medieval period, soap making evolved from accident to art. The Islamic world, particularly in cities like Aleppo and Damascus, became centers of soap production. They developed sophisticated techniques using olive oil and bay oil, creating what we now call Aleppo soap, one of the first hard soaps that could be stored and traded over long distances. In Europe. Soap making guilds emerged in France, Italy, and Spain. The famous Marseille soap, made from olive oil and sea salt, became a standard that influenced soap making across the continent. However, soap was still a luxury item. Most people used alternatives like sand, ash, or simply water for cleaning. Medieval soap makers didn't invent entirely new chemistry, but rather they refined techniques, experimented with different oil combinations, and developed better methods for controlling the saponification process. The 18th and 19th centuries brought dramatic changes that transformed soap from a luxury to a necessity. Several key developments converged to make this possible. First, in 1791, the French chemist Nicolas Leblanc invented a process for producing soda ash, also known as calcium carbonate, from salt, making the alkali component of soap more affordable and readily available. And this was crucial because previously alkalis had to be laboriously extracted from the ash of plant material. Then, in 1823, another French chemist, Michel Cherval, figured out the actual chemistry behind saponification. He demonstrated that fats are composed of glycerin and fatty acids, and that soap formation involves splitting these apart and recombining the fatty acids with an alkali. This scientific understanding enabled soap makers to now control the process with greater precision. The Industrial Revolution brought mechanization to soap production. Companies like Procter and gamble founded in 1837. And Lever Brothers, founded in 1885, began mass producing soap using steam powered machinery. Something of interest is the development of one particular brand of Ivory soap. According to legend, the floating nature of Ivory soap was discovered by accident. In 1878, a worker supposedly left a soap mixing machine running too long, whipping excess air into the batch. When the soap hardened, it was lighter and could float in water. Customers actually liked this feature because it was easy to find the bar in a bath or laundry tub. And here is where the second subject of this episode now enters the discussion. Detergents. But before I get into detergents, I should explain one of the major problems with soap, hard water and soap scum. In hard water, there are magnesium and calcium ions floating about. These can latch onto the hydrophobic ends of soap molecules, rendering the soap molecule unable to create micelles with dirt and oil. The result is what we know as soap scum, which can often accumulate on the sides of your bathtub or in your shower. This is a bigger problem the harder the water you're using is. And hard water is just water with a high amount of dissolved minerals such as magnesium and calcium. If you wash in hard water, it is much more difficult for soap to develop a lather. A traditional solution to this problem was the use of washing soda, also known as sodium carbonate. Washing soda would soften the water, allowing the soap to work more effectively. The early 20th century witnessed the emergence of synthetic detergents from German chemical research. During World War I, Germany faced shortages of fats needed for soap production, spurring chemists to develop alternatives. They created synthetic cleaning agents from petroleum and coal tar derivatives. The real breakthrough came in the 1930s when chemists at Procter and Gamble developed the first synthetic household detergent. So what exactly is a detergent and how is it different than soap? Detergents are basically synthetic soaps. They function in a manner similar to soaps. The detergent molecules have both a hydrophilic and hydrophobic end, similar to soaps, and they form micelles around dirt and oil, just like soaps. However, in detergents, the hydrophobic end doesn't want to connect with magnesium or calcium in hard water. That means that detergents, unlike soap, doesn't produce soap scum and leave a residue behind. World War II accelerated detergent development as fats and oils were needed for the war effort. Synthetic detergents became not just alternatives to soap, but in many cases, superior cleaning agents. They worked better in cold water, didn't leave residue, and could be formulated for a specific cleaning task. As the use of detergents increased dramatically, a problem arose. Starting in the 1940s and 50s, detergent makers added phosphates, usually sodium tripolyphosphate. These acted as builders, which meant that they softened water, boosted cleaning power, and helped suspend dirt. This made detergents with phosphates very effective, especially in areas with very hard water. When household wastewater entered lakes and rivers, however, the phosphates didn't break down. They enriched the water with nutrients, and that might sound like a good thing, but it wasn't. These excess nutrients fueled the explosive growth of algae in lakes and rivers. Thick mats of algae blocked sunlight from penetrating the water, disrupting aquatic ecosystems. When algae died and decomposed, the process consumed dissolved oxygen in the water, suffocating fish or other aquatic life. Lake Erie was famously declared dead due to algal overgrowth. Most consumer detergents worldwide are now phosphate free, though some industrial and institutional cleaners still use them in controlled contacts I'd like to give some attention to a special type of product that most of you are also familiar. Shampoo. If you remember back to one of my episodes on the Origin of Words and Phrases, the word shampoo comes from India. It originally referred to an herbal product that you put in your hair and had nothing to do with soap or cleaning. For much of the 19th century, people washed their hair with bar soap or homemade soap solutions. While it did clean hair, it often left hair rough, sticky, or dull because of soap scum from hard water. Still, commercial hair soaps and perfumed wash solutions began to appear by the late 1800s. Manufacturers marketed liquid hair cleaners under the name shampoo. These were essentially just stronger soap solutions, sometimes mixed with herbs or fragrances. However, they still had the same problem with soap scum. In the 1930s, modern liquid shampoo became popular in the United States. The first widely marketed liquid shampoo in the US was Durene, introduced by Procter & Gamble in 1934. What made it different from the shampoos that came before it is that it was a detergent, not a soap. Most shampoos today contain a blend of surfactants, which are a form of detergent. Detergents enable shampoos to be effective in hard water, offer adjustable strength that ranges from strong degreasers to ultra gentle baby shampoos, and can be customized with conditioners, fragrances, and additives. Simple soaps are actually relatively simple to make. There are numerous artisans who create and sell soaps at local markets worldwide. Soap can literally be made in your kitchen. Detergents, on the other hand, are more complex and typically are only produced at scale using sophisticated equipment. The problems that the people in Babylonia faced almost 5,000 years ago are not that different from the problems that we face today. What has changed is our understanding and the sophistication of the soaps and detergents that we use to clean our clothes, dishes, cars, and ourselves. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Austin Otkin and Cameron Kieffer. My big thanks go to everyone who supports the show over on Patreon. Your support helps make this podcast possible, and I also want to remind everyone about the community groups on Facebook and Discord. That's where everything happens that's outside the podcast, and links to those are available in the show notes. As always, if you leave a review on any major podcast app or in the above community groups, you too can have it read on the show.