Soap Making
What is soap, and how is it made?

Soap is a cleansing agent or detergent, made from animal and vegetable fats, oils, and greases; chemically, the sodium or potassium salt of a fatty acid, formed by the interaction of fats and oils with alkali.  Simply put, it is an oil or fat mixed with ash (lye) also [The impure potassium carbonate obtained by leaching wood ashes].

Oils and fats used are compounds of glycerin and a fatty acid, such as palmitic, or stearic acid. When these compounds are treated with an aqueous solution of an alkali, such as sodium hydroxide—a process called saponification—they decompose, forming glycerin and the sodium salt of the fatty acid. The fat palmitin, for example, which is the ester of glycerin and palmitic acid, yields sodium palmitate (soap) and glycerin upon saponification. The fatty acids required for soapmaking are supplied by tallow (animal fat), grease, fish oils, and vegetable oils such as coconut oil, olive oil, palm oil, soybean oil, and corn oil. Hard soaps are made from oils and fats that contain a high percentage of saturated acids, which are saponified with sodium hydroxide.

[SoapCandle's soap's are all made with vegetable oils, and added glycerin.]

Tallow alone yields a soap that is too hard and too insoluble to provide satisfactory lathering, and therefore it is usually mixed with coconut oil. Coconut oil alone yields a hard soap that is too insoluble for use in fresh water; it lathers in salt water, however, and is used as marine soap. Transparent soaps usually contain castor oil, high-grade coconut oil, and tallow. A fine toilet soap made of high-grade olive oil is known as castile soap. Shaving soap is a potassium-sodium soft soap, containing stearic acid, which gives a lasting lather.

Soap's History

The purifying agents mentioned in the Old Testament (see Jeremiah 2:22 and Malachi 3:2) were not true soaps but were a product of tree bark ashes alone. The 1st-century Roman historian Pliny the Elder described various forms of hard and soft dye-containing soaps known as rutilandis capillis, which had previously been used by women to cleanse and impart brilliant colors to the hair. Soapmaking was common in Italy and Spain during the 8th century. By the 13th century, when the soap industry was introduced from Italy into France, most soap was produced from the tallow of goats, with beech ash furnishing the alkali. The French, after experimentation, devised a method of making soap from olive oil instead of from animal fats and, about 1500, introduced their discoveries into England. The industry in England grew rapidly and in 1622 was granted special privileges by King James I. In 1783 the Swedish chemist Carl Wilhelm Scheele accidentally simulated the reaction that occurs in the present-day boiling process of soapmaking, described below, when he boiled olive oil with lead oxide, producing a sweet-tasting substance that he called Ölsüss, which is now known as glycerin. This discovery by Scheele led the French chemist Michel Eugène Chevreul to investigate the chemical nature of the fats and oils used in soap; Chevreul eventually discovered, in 1823, that simple fats do not combine with alkali to form soap but are first decomposed to form fatty acids and glycerols. Meanwhile, the manufacture of soap was revolutionized in 1791 by the French chemist Nicolas Leblanc, who invented a process for obtaining sodium carbonate, or soda, from ordinary salt. In the early American colonies, soap was made from rendered animal fats and was processed mainly in the household, but by 1700 many areas derived their main income from the export of ashes and fats used in soapmaking.

[Above diagram shows soap on a piece of fabric (similar reaction occurs with skin).

Once soap has dissolved in water, its molecules will surround any patch of dirt on the fabric, forming a ring around it called a micelle. This occurs because soap molecules have "ends" that differ in their properties. One end is attracted to water (hydrophilic), the other is attracted to nonsoluble substances such as oil and grease (hydrophobic). When soap molecules attach themselves to grease stains, they form a new surface that is soluble in water. Cleaning action is the absorption of dirt and grease into the center of soap micelles, which transforms a stain into a soluble substance that can be rinsed away.

Compiled by Cathy Wolfram

"Soap," Microsoft® Encarta® Online Encyclopedia 2002
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