When walking through a store, or even while watching television, one notices that there are several different kinds of soap. They come in a variety of shapes, sizes, and colors, and it seems that each is used for a specific purpose. One may wonder, how did this business get so complex?

        In order to fully appreciate the history of soap, one must first understand what soap is. A soap molecule contains two portions: a carbon chain and an ionic end of sodium or potassium. The carbon chain of the soap molecule is lipophilic, that is it is generally attracted to organic compounds (Aloves@ fatty compounds) while the ionic sodium or potassium end of the molecule is hydrophilic, that is it Aloves@ water. Thus, the molecule is simultaneously active for both fatty and watery materials¹. It is these concepts of lipophilic and hydrophilic that allow one to understand how soap works. Since water and the oil produced by the skin (which contains the dirt) do not mix, washing with water alone will not remove the dirt and oil on the skin. This problem is solved with soap. When washing with soap, the lipophilic part of the molecule mixes with the oil and the hydrophilic portion of the soap molecule mixes with water. Therefore, when the soap suds are rinsed away, the oil and dirt are also removed².

        Soap is produced when a fatty acid is combined with an alkali (otherwise known as a base) in a process called sponification. The alkali causes the fatty acid to be split into two parts: the Amajor fatty part@ (a carbon chain) and glycerin. Once this happens, sodium or potassium joins with the carbon chain to produce soap³. Soaps are usually produced by combining fats or oils with lye, soda (Na₂CO₃), or potash (K₂CO₃)². But how did this process get started?

        Well, the Romans are often credited with the discovery of soap around 1000 B.C. Legend says that the fat dripping off an animal sacrifice dripped into the ashes of the fire below it. Somehow this mixture made it into the Tiber River where women were doing laundry. They discovered that the clothes came clean easier with this substance. Since the hill they were on was Sapo, the Abarbarian confection@ was named after the hill, which became the modern word Asoap@². However, contrary to legend, the method of producing soap by combining fat and potash was first employed around 3000 B.C. In fact, directions for soapmaking have been found on Sumerian clay tablets dating around 2500 B.C. These recipes called for ashes of wood fires to be mixed with water, which would produce diluted solutions of potash. This solution was boiled while fat was dropped in and allowed to dissolve slowly. A dilute solution of soap was then produced⁴. However, Singer et al.⁵ argue that although soap was produced, soap itself was not actually known to them. They point out that the terms currently understood to mean soap are doubtful, the recipes never actually mention that soap is produced, and soap is never actually separated from the solution or given a special name. In fact, the first concrete evidence of knowledgeable soapmaking is found in ancient Rome. The ruins at Pompeii revealed a soap factory with finished bars³. It must be noted that although the Romans are famous for their public baths during this time, the soap was too harsh for the skin. Thus, soap was used only for clothing².

        The practice of bathing declined during the Middle Ages in Europe, and it was thought that bathing was dangerous and unsanitary. However, soap was still produced for the purpose of washing clothing. The production of soap throughout this time period was very secretive, using methods which were passed down by word of mouth. If a recipe needed to be written down, it was often written in a secret code⁴. Little advances in soapmaking were made during this time period. It wasn=t until the 18^th century, when bathing was popular again, that new developments were made. This is partially due to an increased demand by the public for Adomesticated soaps@, or soaps that could be used for bathing⁴.

        Around 1500 A.D. it was discovered that many soaps were being produced throughout Europe and that the ingredients in these productions of soap started to differ from region to region. For example in southern Europe, vegetable oils were used, while in northern Europe tallow (cow fat) was usually used⁶. In Colonial America, lye was made by mixing water and wood ashes in a barrel with small holes in the bottom and then catching the drippings. Since the production of soap needs fat as well as lye, this usually accompanied the butchering of farm animals². As a result, soap industries developed in these different regions, and each produced its own kind of soap⁶. Colonial America, however, was the exception. Soap companies did not began to appear until the early 19^th century².

        The 18^th century brought new discoveries in the process of soapmaking. During this period, the living standards in Europe were increasing, causing bathing to become popular again. This caused an increase in the demand for soap⁴. This increased demand came at a time when previous soap production had caused a shortage in the supply of trees to obtain potash. Thus, numerous attempts to find new methods were being made. The race for the first new method was won by the Frenchman Nicholas Leblanc in 1790 with his process of converting common salt (NaCl) to the alkali. The Leblanc process involved the use of salt, sulfuric acid, limestone, and coal to produce soda (Na₂CO₃). In modern chemical reaction format, the process resembled the following:

The Ablackash@ described by Leblanc consisted mainly of sodium carbonate (Na₂CO₃) and calcium sulfide (CaS). The sodium carbonate was then extracted with water and allowed to crystallize. By the middle of the 19^th century Leblanc=s process became the main method in soap production⁷. Although the Leblanc process had the advantages of being convenient, easier, and inexpensive, it produced harmful chemicals and the residue left from the blackash was causing pollution problems. Thus, the ammonia-soda process was discovered in 1811 by Augustin Jean Fresenel. Fresenel=s process began with common salt (NaCl) saturated with ammonia (NH₃). This was reacted with carbon dioxide (CO₂) to produced sodium bicarbonate (NaHCO₃). When the sodium bicarbonate was heated, soda (Na₂CO₃) was produced. By 1902 this process was widely employed and is still in use today⁷.

        Around the same time as the development of these new processes by Fresenel and Leblanc, other chemical advances regarding soap were made. Soap production up until this time was a process of trial and error, luck, and superstitions³. For example, although it was known that adding salt at the end of the boiling process would produce hard soap (a process originating in Gaul around 800 A.D.⁴), it was not quantitatively controlled until the late 18^th century when these new discoveries were made⁶. The first chemist to influence the understanding of soap production was Otto Tachenius. Tachenius, in his book Hippocrates Chimicus (1666), was the first to give a distinct definition of salt: Aall salts are composed of two parts, of acid and alkali@. He further added that soap was the salt of an oily acid. Tachenius= statements were not recognized by the community of the time, and it wasn=t until Michel Eugene Chevreul rediscovered the idea in 1816 through his laboratory work that the definition of salt as Tachenius defined it was accepted⁸.

        Since soapmaking is considered a dangerous and smelly process, many rely on companies to produce it. Today the soap industry is a thriving enterprise containing many well-known companies such as Proctor and Gamble, Dial, Ivory, Zest, Jergens, and Lever Brothers. What most people probably do not know about the soapmaking industry is that the same methods of production are still employed today as they were in the late 1800's to early 1900's. That means that most soaps are made from tallow. The exception occurs only when Avegetable oil@ appears clearly on the label. Also, few companies actually make their own soaps. Instead almost all soaps on the market are produced by five independent soapmakers. In addition, of these five soapmakers, only three make their own soap base, meaning that virtually all soaps contain the same base despite their differences in appearances⁹.

        Although most soap is produced by industries, it can still be made in the home. Ann Brmason=s book Soap: Making It, Enjoying It actually started a revival of soapmaking in the home¹⁰. For persons interested in making his or her own soap, numerous recipes can be accessed through the Internet and others are available in books at bookstores and in the libraries.
 

References

1. Kranzberg, Melvin, Pursell, Carroll W., Jr., Eds. In Technology in Western Civilization;
            Oxford University Press: London, 1967; Vol. 2, p. 190.

2. Cobb, Vicki. The Secret Life of Cosmetics; Harper Collins Publishers: New York, 1984;
            pp. 10-12, 16-19.

3. The Soap Factory. http://www.alcasoft.com/soapfact/history.html (accessed Oct. 1998).

4. Salzberg, Hugh W. From Caveman to Chemist: Circumstances and Achievements;
            American Chemical Society: Washington, DC, 1991; pp. 6-7, 74.

5. Singer, Charles, Holmyard, E.J., Hall, A.R., Eds. In A History of Technology; Oxford
            University Press: London, 1956; Vol. 1, p. 260-261.

6. Singer, Charles, Holmyard, E.J., Hall, A.R., Williams, Trevor I., Eds. In A History of
            Technology; Oxford University Press: London, 1957; Vol. 3, pp. 703-705.

7. Hudson, John. The History of Chemistry; Chapman & Hall: New York, 1992; p. 247-248.

8. Partington, J.R. A Short History of Chemistry, 3^rd ed.; Dover Publications, Inc.: New York,
            1989; p. 60, 221-222.

9. Touchstone Natural Products Marketing. http://www.monsterbit.com/touch/soap1.html
            (accessed Oct. 1998).

10. Sappo Hill Soapworks. http://www.sappohill.com/soaphist.htm (accessed Oct. 1998).