Pages Menu
Categories Menu

Posted by on Apr 1, 2016 in TellMeWhy |

How Is Soap Made?

How Is Soap Made?

When you wash with soap, you are using a cleaning material made chiefly of animal fats, vegetable oils and an alkali chemical. In the soap factory, the soap materials are combined with water at high temperature and pressure. This substance is next put in a huge mixer, where it is churned into a creamy mass.

Other ingredients, such as coloring, perfume, and germ killers, are then added. This creamy mass is then poured into molds, where it continues to react, while generating heat. To make soap bars, the soft soap is squeezed through a machine that forms it into one long bar, which is then cut into smaller bars and stamped with the manufacturer’s name, but the saponification process continues for a few weeks, until all of the lye has reacted with the oils.

Soaps are often super fatted, so after all of the lye has reacted with the fats, there are still fats left over. This is important for two reasons. 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 nice 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.

Polyethylene glycols such as PEG-6 methyl ether may be added as surfactants, detergents, emulsifiers (to make the dyes and perfumes blend evenly), or as thickeners.

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.

Content for this question contributed by Desiree Douglas, resident of Santa Cruz, Santa Cruz County, California, USA