Soap

Chemically speaking, soaps are alkaline salts of higher fatty acids (e.g. coconut fat, palm kernel fat, palm oil, olive oil, sunflower oil, corn oil, soybean oil and animal fats such as tallow or lard, etc.). In today's language, "soap" is generally understood to mean cosmetic fine soaps or toilet soaps. These soaps are generally solid preparations made from the sodium salts of fatty acids.

Soaps are used in their surfactant effect as cleaning agents for the body surface. As textile detergents they have lost their importance. They form insoluble calcium and magnesium salts (so-called lime soaps) in so-called harder water, which are deposited on the objects in use.

Soap manufacturing process

For production, fats are mixed with lyes (caustic soda or potash lye) and boiled (saponified). The process is known as soap boiling. The fats used (usually glycerol esters of linear long- or medium-chain fatty acids) are split into glycerol and the respective alkali salts of the fatty acids (the actual soaps) during this process. The viscous emulsion obtained during soap boiling is called soap glue. The actual soap is separated from soap glue by adding saline solution.

Alternatively, soaps can be produced directly from free fatty acids (and not their glycerol esters) (so-called lye saponification) by converting the free fatty acids into their alkali salts after adding lye. Suitable fatty acids for this process are for example lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and ricinoleic acid.

The consistency of the soap depends among other things on the chain length of the fatty acids. The longer the chain length of a saturated fatty acid (e.g. stearic acid or palmitic acid) the more consistent the final soap product.

Essential for the consistency of a soap, however, is the saponifying alkali metal (sodium or potassium). If the soap core is extracted from the soap glue by adding sodium hydroxide solution, a more solid soap tends to form, the curd soap. Curd soap is formed in blocks and dried. If the soap core is obtained by adding potassium hydroxide solution, potassium salts of the fatty acids are formed, soft to greasy soaps (soft soaps).

Manual soap production from natural products: Soaps can also be produced manually, individually, by cold saponification. Here mostly high-quality natural fats, fatty acids, oils and waxes are used. A precisely measured quantity of caustic soda (NaOH) is added to these natural products. The aim is to achieve only incomplete saponification of the fats and oils. This means that unsaponified free fatty acids remain in the resulting soap product (over-fatting). With the over-fatting of the soap an additional caring effect is achieved besides the actual tensidic effect of the soap.

Washing effect of the soap

Soaps are a mixture of different, longer-chain alkali salts of fatty acids. They belong to the group of surfactants (anionic surfactants). The soap molecules owe their properties to the fact that the supporting fatty acid consists of a long, water-repellent (hydrophobic) hydrocarbon chain and a water-attracting (hydrophilic) part, the so-called carboxylate group (-COO-). Soaps also do not dissolve in water, but form so-called micelles. In pure water the micelles are very small and cannot be seen. Inside these smallest "droplets" are the long, non-polar hydrocarbon chains, while the polar ends protrude into the water. The charges sitting on the ends prevent the micelles from clumping together.

Soaps lower the surface tension of water because they also settle on the water surface. This wetting effect allows the water to come into contact with surfaces much more intensively, which means that the actual cleaning effect of soap and water can only develop in inaccessible places.

The "dissolving of fat" (oil, dust, dirt) from the body surface to be cleaned and its removal via the washing water is the actual and generally valid principle of the cleaning effect of soap.

The long hydrocarbon chains of the soap molecules dissolve easily in small fat droplets. However, the polar ends protrude into the surrounding water. The fat droplet is finally completely enveloped by the soap molecules and detached from the surface to be cleaned. The large number of fat and oil droplets thus coated with soap molecules forms an emulsion in the water, which can be removed at the end of the washing process by rinsing with fresh water.

Liquid soaps

Liquid soaps differ from lumpy soaps in the content of fatty acid salts and in the type of cation of the lye. They generally contain fewer washing-active substances.

Glued soaps (soap glue) are homogeneous masses in which the glycerol is not separated after saponification of the fat (glycerol fatty acid ester); it remains in the product. Cold-boiled soaps are occasionally offered as glue soap. Here, the fats and the lye are saponified at 40 °C and the mass is poured into a container immediately afterwards. Many homemade paste soaps are offered.

Curd soap

Curd soaps are solid soaps and usually consist of the sodium salts of fatty acids. They are obtained by salting out the soap glue, whereby the glycerine is separated. Most commercially available body soaps, including fine soaps, are curd soaps. They are formed in blocks and dried. In trade, mainly cheaper, unscented soaps are called "curd soaps". These play a beneficial role in personal hygiene for (poly)sensitized patients.

soft soap

Soft soaps are liquid or semi-solid soaps which are produced from inexpensive fats or oils by saponification with potash lye. Soft soaps are viscous products and consist of a mixture of potassium salts of higher fatty acids (potassium soaps). As liquids they can be easily added to water and used for cleaning purposes, e.g. in the household.

Abrasive soaps

Contains as additives abrasive substances such as quartz sand, almond bran or rice bran, which serve to remove skin impurities or coarse dirt.

Baby soaps

Well greased toilet soaps. They often contain high quality grease components as well as camomile or aloe extracts with little perfume.

Fine soap (toilet soaps)

Fine soaps, also called toilet soaps, are generally preparations based on pure, odourless curd soaps (often based on coconut oil) and are mainly used for washing hands. They are mixed with refatting agents (caring additives, such as lanolin) as well as fragrances and colourings.

Deodorant soap

Deodorant soaps are usually pure curd soaps to which a deodorant has been added.

Refatting soaps

Refatting soaps should have a "refatting" effect during the normal washing process with soaps - which naturally leads to the degreasing of the skin. They should therefore return grease to the skin. For this purpose, fats are often added to fine soaps (main component: curd soap) or an excess of fats is used in saponification so that not all fats are saponified. This chemical trick gives the feeling that an over-fatting soap has a less aggressive effect, less destroys the natural fatty acid coat.

Cream soaps

Cream soaps are soaps which contain a particularly high proportion of over-fatting agents - such as vaseline or lanolin.

Glycerine soap

Glycerine soaps (also called transparent soaps) are soaps which have a high (unbound) glycerine content. These soaps are cloudy to glassy transparent (transparent soaps). They are also easy to melt (like many waxes) and are therefore also used as craft soap.

Transparent soap

Glycerine soaps belong to the transparent soaps. By adding glycerine, sugar, ethanol the crystallization of the solidified supercooled soap solution is prevented. The final soap product remains transparent.

Shaving soap

Preparation for wet shave. The shaving soap is stirred into lather with a wet brush and then applied. Shaving soap is usually a mixture of sodium and potassium soaps, humectants, water and fragrances. This Na/K double saponification makes the shaving soap softer and easier to apply. Shaving soap is used in the form of round soap bars as well as in a

bar form ("sticks") are offered.

Foaming shaving cream

Foaming shaving creams usually consist of a potassium soap or a mixture of potassium soap and a foaming tenside (e.g. triethanolamine soap). Often they also contain an over-fatting agent like e.g. vaseline or lanolin as well as water-binding (i.e. moisturizing) substances like glycerine or sorbitol. In most cases, fragrances are a component of the formulation. Shaving creams lead to a swelling of the hair keratins and allow a smooth gliding of the razor blades on the skin. The typical pearly shine of the creams is caused by a content of free stearic acid.

Non-foaming shaving cream

Non-foaming shaving creams are usually applied to the previously washed skin. Like all shaving cosmetics, they cause the hair to swell. The shaving creams prevent the hair from drying out and facilitate a smooth gliding of the razor blades on the skin. Non-foaming shaving creams are usually somewhat more complex formulas. They consist of stearin derivatives with emulsifiers as e.g. the foam-stabilizing triethanolamine; furthermore, they consist of non-ionic surfactants. The formulations are complemented by simple lubricants (e.g. paraffin oil, vaseline, wool wax), moisturizers (e.g. glycerin, sorbitol etc.) as well as further additives (alginates, methyl cellulose as swelling agent) and preservatives. Usually fragrances are a component of the recipes.