A soap, or detergent, is a material used for getting things clean. The first soaps were made thousands of years ago, and they are still made in much the same way today.
To make a simple soap you need animal or vegetable oil and a chemical such as caustic soda. In very ancient times this was achieved by adding lime (made from chalk) to olive oil, or by adding the ashes from a fire to tallow (animal fat). It was a simple as that. If caustic soda was added, the result was a hard soap. If ash was used, it gave a soft, liquid soap.
The only difference between ancient times and modern times is that modern soaps and detergents are made of many substances, so that they work far better than simple soap alone.
When you make a soap it is like millions of little balls of soap chemical. The outside of the ball attracts water, but the inside is attracted to dirt, most of which is oily.
Most of the dirt that is not oily is dust. Dust is really tiny. Have you even seen the demonstration of rubbing a balloon against a jumper? The balloon sticks to the jumper because of electricity. Dust gets attracted to clothes in exactly the same way.
So what a soap has to do is to get rid of the electricity holding the dust and also get rid of the oily dirt?
If you put soap into water with dirty clothes or plates nothing would happen. It only happens when you rub. By rubbing, you push the soap against the dirt and dust. The soap then wraps itself around the oily materials because it likes oil. It wraps itself around electrically charged dust because it likes electrical charges. The outside of soap likes water, so the oil or dirt stops sticking to clothes and plates and sticks to the soap, where it can drift out into the water and can be rinsed away.
Soaps are still made using animal tallow, or oils from plants such as palm oil, coconut oil, olive oil, and laurel oil.
Each kind of oil is different and gives a soap with its own special feel. That is one reason why so many kinds of soap are made. Seed oils give mild soaps. Soap made from olive oil is called Castile soap and is extra mild.
Thinking back to ancient times again, you can see that soap could be made by accident if olive oil were dropped into the ashes of a fire. The Babylonians were probably the first people to make soap intentionally about 4000 years ago. The Egyptians mixed oils and ashes in water to make soap to wash in, and also wash wool before it was spun, and to clean clothes.
The word soap comes from a very early German word for animal fat, and was changed by the Romans into a Latin word that has been changed again into our modern word soap. That is because the German 'Celts' made soap before the Romans. The Romans didn't wash with soap. Instead, they put oil on their bodies and scraped it (and the dirt) off. Romans only used soap as a kind of hairdressing.
People in the Middle East took soap making very seriously in the Middle Ages. People from the Middle East were actually the world's first chemists. In fact their word for 'ash' gives us our modern word 'alkali'. By knowing how to make soap properly, the Islamic world was able to made soap that was always the same.
Those people who could make soap tended to hold on to their secret as soap making was a good way to make money. In the Middle Ages, soap makers formed guilds in many countries of Europe to help to protect their secrets.
The first time bars of soaps were made on a large scale was in the 18th century. Soap became popular as doctors told of how washing with soap was important to staying healthy. Before that many people only washed a few times a year to keep body smells (from bacteria) under control.
Andrew Pears started making a high-quality, transparent soap in London in 1789. William Hesketh Lever and his brother, James, bought a small soap works in Warrington, N.W. England, in 1886 and founded what is still one of the largest soap businesses. They called it Lever Brothers and today it is called Unilever.
For thousands of years, soap was hard or soft, but it was not liquid. One of the problems with using hard soap when washing clothes is that the soap often gets stuck in the fibres. Liquid soap (which can be made into a powder or flakes) does not do that.
Liquid soap was invented in the 1880s. The B.J. Johnson Soap Company introduced Palmolive liquid soap in 1885 made of PALM oil and OLIVE oil. It was so popular the Johnson Soap Company changed its name to Palmolive. By the early 1900s, Tide washing soap (it was not a washing powder then) appeared on the market for cleaning clothing and bathrooms.
When you make soap, you might think that the ideal would be when you used just enough oil to combine with just the right amount of alkali. However, if you use more fat than is needed, it produces a material called glycerine, which is a moisturiser. In this way it is easy to make soaps that contain 'moisturiser'. Moisturisers stop hands drying out and cracking. Sometimes extra oil is added when the process is nearly finished. Jojoba oil is often added at this stage.
As you can imagine, you cannot simply mix ashes with oil. Not only would it be full of gritty bits, but the alkali is locked up in the ashes, and it has to be released. So, for centuries, the alkali used to make soap was made using ashes dumped in a tub of rainwater and left to soak. This was called lye. The alkali seeped out from the ashes and so made a liquid that could be mixed with the oil or fat. Soap makers found out when the concentration of lye was correct by floating an egg in it. If it floated, it was ready.
The business of making the alkali reliably was changed in the age of chemistry, English scientist, Sir Humphry Davy, who discovered so many substances in the early years of chemistry, discovered how to make an alkali (caustic soda) that was always the same.
The reason that getting the correct proportions of alkali to oil, or having more oil than needed, is for another important reason: a pure alkali can burn the skin if it is not all used up in the chemical reaction with the oil.
When the lye and oil are placed in a tub, they are stirred until they mix to make something that is like thin pudding. After this, other oils can be added to give special aromas and so on.
At this stage the soap is poured into moulds. The two main ingredients continue to combine for at least a day, and during this process the soap hardens.
In large automated factories, the whole process is speeded up by using hot ingredients. The soap is then reboiled and salt added. Adding salt makes the soap turn solid.
Sand or pumice may be added to produce a scouring soap. The scouring agents serve to remove dead cells from the skin surface being cleaned. This process is called exfoliation.
Tiny particles of metals are commonly added to certain soaps. Titanium dioxide powder is commonly used to make "white" soaps. Metals used like this also kill bacteria. Because some of the metal is left behind on the skin, it helps to stop bacterial recolonising the skin for many hours and so is a deodoriser.
Is a detergent the same as a soap? Nearly. A detergent is a family of compounds that are similar to soap but are more soluble in hard water. Detergents are more aggressive than soaps, and do not contain any moisturiser, which is why they are not used for body or hand washing.
