Soap . . . we use it for everything. Basically, soap is composed of fat (from animals or plants) and an alkali, like ashes. The ash, mixed with water, causes the fat to break down into glycerine and sodium salt.

Until very recently, it was NOT the sort of thing you wanted to rub on your body!

The first soaps were probably used to clean fabrics, and possible hair, but not skin. These soaps would have been stinky, caustic, and abrasive.

The word 'soap' comes from the Celtic word Saipo. Wood ash was mixed with water, then animal fat was added. When the mixture boiled, more and more ash was added as the water evaporated. Soap cleaned clothes because it soaked into the fabric and lifted up dirt, which was then carried away in the rinse water.

We know that the Babylonians, the Egyptians, the Israelites, the Celts, the Greeks and the Romans, all had soap--but again, for clothes. When the Romans went into their baths, they we cleaned off by slaves who used scraping tools, and rubbed oil over the skin--not soap.

The Arab world developed milder soaps, using vegetable oils instead of animal fat and adding scent. We know of this because an 8th century chemist in Iran named Jabir, or Geber, ibn Hayyan wrote about it.

Europeans began to add slaked lime to soap in the Middle Ages because it got rid of some of the fat, and the soap would then be less rancid. Soapmaking became a big industry throughout Europe. Spain added another innovation: they boiled the soap with brine until the soap floated to the surface. That way, lye and bits of unwanted dirt would settle at the bottom of the vat. This soap was called Castile, for the city in Spain.

The soap trade became big business in Britain, where sassafras oil from the colonies was imported to make soap. The government levied a tax on soapmakers until the 1850s, and earned an estimated one million pounds per year from it!

One British manufacturer, Andrew Pears, used alcohol to make a transparent soap, way back in the late 1700s. Pears Soap is now part of Unilever.

As wood ash become harder to get, scientists from France found new ways to make soap. CavemanChemistry describes the discoveries they made.

Today, soap is made in several ways. Instead of boiling, some factories rely on chemical reactions to create soap via a "cold process." Other makers use boiling or semi-boiling methods. In modern factories, vats have been replaced by 50-ft tall cylinders.

Fatty acids replace animal fats and are processed by hydrolysis , and many chemicals are added, depending on the desired end result. Your soap probably includes perfumes and coloring. Antibacterial soap includes a pesticide called triclosan. Other additives make soap dissolve quickly, lather up, maintain a liquid form, clean in salt water, or last longer on the shelf.

Soapmaking is also a cottage industry. Now that you know how nasty ancient soaps were, and how today's products are filled with chemicals, you may want to investigate making your own soap as an option. If that's the case, check out the Aussie site SoapNaturally, or some of the books listed above.