The Science of Soap


Soap is an important part of everyday life. Most homes make use of a variety of soaps for different cleaning purposes. Soaps now come in different shapes and sizes. There are traditional solid soap bars and liquid soaps. There are scented soaps and non-scented ones, as well as creamy soaps and clear ones. A bit of the history of soap is looked at here together with some of the raw materials used to make it and how it works.

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The History of Soap

Soap has been around for a very long time. Around 2800BC, the Ancient Babylonians were the first to produce materials similar to soap, according to evidence discovered by archaeologists. In a clay tablet found from around 2200BS, there is a soap formula inscribed. The ingredients were water, an alkali, and cassia oil.

There is also evidence of the Ancient Egyptians using soap a little while later in 1550BC. The Ebers papyrus indicates that these people used a combination of vegetable and animal oils and some alkaline salts to create their own version of soap. They used this for their regular baths.

Other latter kingdoms and empires also made use of their own local versions of soap. This includes the Roman Empire, Ancient China, the Middle East, Medieval Europe. As travel, trade, and exports started to grow, this also led to the sharing of ideas, raw materials, and soap products.

What is Soap Made Of?

In its basic chemical form, soap is the name given to the salt formed from a fatty acid. These salts play a key role in the commercial production of soap. The two basic ingredients of soap are fats or oils and lye, which is the alkali compound sodium hydroxide. Different fats and oils can be used to give a wide variety of different soaps with unique quality and texture.

When solid fats are used, the resulting soap is hard and resistant to dissolving when left in a soap dish, for example. Examples here include coconut oil, palm oil, and fats derived from beef and pork. For softer and milder oil, canola oil, soybean oil, and olive oil can be used instead.

Saponification is the reaction process between liquid fats and lye. This is done with heating, and the result is a thickening of the reaction mixture. At this stage, important additives such as scents and dyes are added in. As the liquid begins to harden, it is poured into the desired molds. There it continues to react and harden into shape. The full saponification reaction can take a few weeks to complete. Excess fat is often added at the beginning of the reaction to make sure that all the alkali reacts to avoid irritating the skin when the alkali soap is used.

The products of saponification are soap and glycerin. In commercial production, the glycerin is removed and sold separately. Many recreational soap makers keep the glycerin in. This adds a softening and nicer feel to the soap. Preservatives and antimicrobials are also added.

How Does Soap Work?

Whether soap is made using the basic process described above or a soap-like substance is extracted from some soap plants as was done a long time ago, the most important part is how it performs its function. Soap often looks and smells great, but its ability to clean is very important.

Soap molecules love water on one end and hate water on the other end. To clean, soaps act as surfactants. This means they emulsify or surround and separate out the oils in the cleaning water. This allows the oily dirt to be carried away in the water.

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