You have done a little gardening and your hands are soiled (sic!). Inside. Turn on the tap. Hands in the warm water and get hold of a bar of soap. Gently caress the soap. Squeeze the soap. Get a luxurious lather from the soap. Rinse. Hey presto. Clean hands! Itís taken for granted. A little miracle has just taken place because of a little product called soap.
The first soaps were the saps of certain plants, such as the Soap Plant . The roots were crushed in water to form a lather and could be used as a general purpose soap or shampoo for our hunter/gatherer forebears.
Soapberry, Soapbark and Soapwort (also contain the same main ingredient, the compound called saponin, which forms the foamy lather. Believe it or not it is also a toxin and was used to stun fish leaving them floating on top of the surface ready to catch!
Stone Age people realised that fats reacted with alkalis in the ashes left over from a fire to produce saponified compounds such as sodium stearate and the related potassium stearate
Today, soaps are made from fats and oils that react with lye (sodium hydroxide). Solid fats like palm oil, tallow (rendered beef fat), coconut oil or lard (rendered pork fat), are used to form bars of soap that stay hard and resist dissolving in the water left in the soap dish.
Oils such as olive oil, soybean oil, or canola oil make softer soaps. Castile soap is any soap that is made primarily of olive oil, and is known for being mild and soft.
As warm liquid fats react with lye and begin to saponify, they start to thicken. It is at this point dyes and perfumes are usually added to the soaps. The hardening liquid is then poured into moulds, where it continues to react and generate heat. After a day, the bars can be cut and wrapped as bars of soap, but the saponification process continues for a few weeks, until all of the lye has reacted with the oils to produce the soap.
Soaps are often superfatted, so after all of the lye has reacted with the fats, there are still fats left over. There are two reasons that this is important. First, the resulting soap is easier to cut, and feels smoother on the skin. Second, the extra fats make sure that all of the lye reacts, so no lye is left to irritate the skin, and the resulting soap is not too alkaline.
The saponification process results in about 75% soap, and 25% glycerine. In homemade soaps, the glycerine is left in, as it acts as an emollient (skin softener) and adds a pleasant feel to the soap. In commercial soaps, the glycerine is often removed and sold separately, sometimes showing up in skin moisturizers that remedy the damage done by drying soaps.
Commercial bar soaps contain sodium tallowate, sodium cocoate, sodium palmate and similar ingredients, all of which are the results of reacting solid fats (tallow, coconut oil, and palm kernel oil respectively) with lye.
To these ingredients, they add fatty acids such as coconut acid and palm acid (the fats in coconut oil and palm kernel oil) as the extra fats needed to ensure the lye is completely reacted, and the soap has a good feel.
Glycerine is added as an emollient and texture enhancer. Sorbitol is another emollient used along with glycerine. It is often added to help make glycerine soaps more transparent. Titanium Dioxide is added to make the soap opaque. Pentasodium pentetate, tetrasodium etidronate and tetrasodium EDTA are added as water softeners, and to protect the dyes and perfumes from the effects of metal ions in the mixtures. These compounds lock up calcium and magnesium in the water, preventing them from reacting with the soap to form insoluble soap scum.
Not all bars that lather contain just soap. Many contain the same detergents that you find in shampoo along with soap.
BHT (Butylated Hydroxytoluene) is sometimes added as an anti-oxidant preservative to keep the oils from going rancid.
Antibacterial soaps usually contain triclosan or triclocarban as the active anti-bacterial ingredient.
So the next time there is a bit of dirt on you, use your soap with real insight.
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By Sean Glynn
(soap | soaps) Self appointed soap expert.
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