Questions answered

By Sherry Seethaler

SAN DIEGO UNION TRIBUNE
November 3, 2004

QUESTION: I know that soap made in the 19th century was made from animal fat. How does a bar of soap made today differ from that made with animal fat, and what did early people do for bathing before they had soaps made from animal fat?

ANSWER: The earliest accounts of soap-making date from 2800 B.C., but the process seems to have been independently discovered by many different civilizations and may have been known even in prehistoric times. However, soap was initially used for purposes other than bathing, for example to prepare wool for dying.

Some early cultures did emphasize personal cleanliness, including the Romans and the Greeks, who rubbed themselves with fine sand and oil and removed the mixture with a metal instrument called a strigil.

Soap (old-fashioned and modern) works by helping oil and water mix. Soap consists of linear molecules with an electric charge on one end, which can be created by treating animal fat with a strong base (such as lye).

The charged end of the soap molecule is attracted to water. The neutral end is repelled by water and combines with oil.

Soap-making was an established craft in Europe by the late 17th century. Soaps from southern France, Spain and Italy, made from olive oil, were particularly renowned for their quality. However, soap was heavily taxed and thus considered a luxury item.

Until the mid-19th century, most American colonists, particularly those in rural areas, made their own soap by boiling lye extracted from wood ash with animal fat (which they saved all year). Because it was difficult to get the concentration of the lye just right, this method produced inconsistent results.

The first key advance in soap-making was the invention, in the late 18th century, of a more reliable method for producing a strong base.

The second key advance was the development, during World War I, of detergents. Detergents are made from petroleum, and detergent molecules can be tailored to have specific properties. For example, while soap will bind with the calcium ions found in hard water and produce soap scum, detergents can be made that do not bind with calcium.

Many of today's soaps are actually detergents, or a mix of detergents with soap derived from vegetable oils or animal fats (tallow), with added fragrances, moisturizers, vitamins, etc.

The plethora of cleansing products available and our modern obsession with personal cleanliness can be traced back to an advertising campaign for Lifebuoy soap, begun in the 1930s, that coined the term B.O.

copyright 2004 The San Diego Union Tribune