Student Projects

Independent-learning super-curriculum projects: reading, research and ideas shared by Perse students

Soap – A brief history and what is new?

Jemima F – Y8

Soap is a product that is easily taken for granted in the modern world because it is so readily available and cheap to buy but it is a necessity that saves lives. 1.4 million deaths around the globe every single year can be prevented by hand washing properly with soap. Almost everyone in the world has used it but what is actually in it, how is it made and where did it come from?

A brief history of soap

A soap-like substance was found in clay cylinders in Babylon and is evidence that soap was being created as early as 2800BC. The soap found was a small bar and inscriptions on the cylinder show that it was made by boiling fat and ash.

Liquid soap came much later. According to Wikipedia, liquid soap was invented in the 19th century. William Shepphard patented a version of liquid soap in 1898. Another man named BJ Johnson created a liquid soap using palm and olive oils which his company launched the same year naming it ‘Palmolive’ which is still around today. According to Roman legend, soap got its name from Mount Sapo, where animals were sacrificed. Rain would wash the fat from the sacrificed animals along with alkaline wooden ashes from the fires into the Tiber River, where people found the mixture helped clean clothes. This recipe for making soap was relatively unchanged for centuries.

What’s in soap?

The basic structure of all soaps is essentially the same, consisting of a long hydrophobic (water-fearing) hydrocarbon “tail” and a hydrophilic (water-loving) anionic “head”. An example of a soap molecule structure:

CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COO − or CH 3 (CH 2) n COO −

The length of the hydrocarbon chain (“n”) varies with the type of fat or oil but is usually quite long. In making soap, triglycerides in fat or oils are heated in the presence of a strong alkali base such as sodium hydroxide, producing three molecules of soap for every molecule of glycerol.

How does it work?

When soap molecules are dissolved in water, their water-loving heads prefer to be next to water molecules, and their water-fearing tails prefer to be next to each other, making a circular structure called micelles. Dirt such as oil, grease and other molecules become trapped inside the micelles and are then removed from the water.

Like synthetic detergents, soaps are “surface active” substances (surfactants) and as such make water better at cleaning surfaces. Water, although a good general solvent, is unfortunately also a substance with a very high surface tension. Because of this, water molecules generally prefer to stay together rather than to wet other surfaces. Surfactants work by reducing the surface tension of water, allowing the water molecules to better wet the surface and thus increase water’s ability to dissolve dirty, oily stains.

With agitation, the dirt is dispersed into the water and removed from the previously dirty surface. In essence, soap molecules partially dissolve the greasy stain to form the emulsion that is kept suspended in water until it can be rinsed away.

As good as soaps are, they are not perfect. For example, they do not work well in hard water containing calcium and magnesium ions, because the calcium and magnesium salts of soap are insoluble; they tend to bind to the calcium and magnesium ions. In doing so, soaps actually dirty the surfaces they were designed to clean. For this reason soaps have been largely replaced in modern cleaning solutions by synthetic detergents that have a sulfonate (R-SO 3 −) group instead of the carboxylate head (R-COO −). Sulfonate detergents tend not to precipitate with calcium or magnesium ions and are generally more soluble in water.

Liquid and bar soaps

Why liquid and bar soaps are different is down to the ingredients and the way they are made. Liquid soap is made using Potassium Hydroxide to saponify its oils whereas bar soap is made using Sodium Hydroxide. Another difference is that liquid soap contains a larger amount of water which essentially keeps it liquid. To test this, according to a website article by Doctor Lisa Bronner, you should take the cap of liquid soap and leave it so some of the water begins to evaporate. After some time, you will notice the liquid soap becomes more of a gel. To restore the liquid soap you can simply add more water. Bar soaps are usually around 5% water but liquid soaps are normally about 61% water.

What creates the lather foam when you rub your hands with soap?

A question website called Quora said that the lather foam is the result of hydrophobic parts of soap reacting with the water. When soap molecules and water are combined with friction, lathering usually occurs. Pretty much every type of soap will cause a lather. The friction causes pockets of air to develop, and each of the air pockets become coated by the oil in the soap. The oil that coats the air bubbles is also attracted to dirt and will trap dirt molecules as it lathers and that is how it cleans.

 How is soap made?

I chose the title of my project when I was making soap at home and realised I knew little about it and was interested to find out more. I created solid bars of soap by melting wax from a soap making kit in the microwave. After it had melted I poured it into different shaped plastic moulds and added flowers and leaves from my garden for aesthetics. I also added old perfume, vanilla essence and also herbs as my scent, trying out different things for each bar. I then waited for it to solidify in the fridge. I was surprised because it solidified very quickly as it cooled down. I then removed it from the moulds and smoothed it out with a knife. I found that bar soaps go less transparent the more you reheat the same wax. The bars at the start were transparent whereas the end bars where translucent almost opaque. I found that some petals did strange things when in the soap. For example, I picked some rose petals and fully submerged them into the hot wax so that no part was sticking out. They instantly went a sort of blue or purple colour probably due to the temperature of the wax. Although this is one of the ways of making handmade soap, most soap is created using machines and is mass produced. Soap factories, usually use similar method except on a much greater scale. The machines can mass produce more precise and perfect soap. Some factories use machines such as lasers to create intricate patterns and designs quickly. Factories are able to freeze the soap very rapidly. Liquid soap needs to be bottled and bars have to be wrapped and sealed. They often create scents for the factory soap using chemicals and they often add colours to make their products more appealing to customers.

The soap production industry

Soap production is a big industry as you can see from the table below.

Below are the 5 countries that exported the highest dollar value worth of soap during 2015:

  1. Germany: US$1 billion (11.1% of total soap exports)
  2. United States: $902.4 million (9.8%)
  3. Indonesia: $531.2 million (5.7%)
  4. United Kingdom: $509.9 million (5.51%)
  5. Malaysia: $505.0 million (5.45%)

The average American family spends upwards of $600 a year on cleaning supplies, according to data from the Bureau of Labor Statistics. But in the future, soap as we know it may no longer exist.

What’s new?

According to Reuters, scientists in England have developed a cleansing alternative that could make soap completely unnecessary.

The handheld device, called Starstream, takes regular cold water and generates bubbles that, when hit with ultrasound, become “micro-scrubbers that can remove dirt and germs from most surfaces.”

The co-inventor of Starstream, Professor Tim Leighton, explained that while the device could be used to make soap, detergent, or bleach more effective, its most impressive feature is its ability to turn cold water into a powerful cleansing agent.

“One of the key factors of Starstream is that it takes any liquid that you’re using and makes it several thousand times more effective,” Leighton says. “So if you’re using soapy water or bleach… it’ll make it more effective,” he said.

Starstream takes only 6 seconds to clean as effectively as soap and water (which takes up to 30 seconds), meaning it could also help conserve water use.

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