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Thursday, August 14, 2008

Soap

Historically, soap has been composed of sodium (soda ash) or potassium (potash) salts of fatty acids derived by reacting fat with lye in a process known as saponification. The fats are hydrolyzed by the base, yielding glycerol and crude soap. Soap is derived from either vegetable or animal fats (tallow). Using rendered beef fat, or palm oil, olive, coconut, palm, cocoa butter, hemp oil and shea butter. Coconut oil provides lots of lather; while coconut and palm oils provide hardness. Most common, though, is a combination of coconut, palm, and olive oils. Using pure olive oil, it may be called Castile soap or Marseille soap.

Many cleaning agents today are technically not soaps, but detergents, which are less expensive and easier to manufacture.

The most popular soapmaking process today is the cold process method, where fats such as olive oil react with lye. Soapmakers sometimes use the melt and pour process, where a premade soap base is melted and poured in individual molds. Handmade soap differs from industrial soap in that, usually, an excess of fat is sometimes used to consume the alkali (superfatting), and in that the glycerin is not removed leaving a naturally moisturising soap and not pure detergent. Superfatted soap, soap which contains excess fat, is more skin-friendly than industrial soap; though, if not properly formulated, it can leave users with a "greasy" feel to their skin. Often, emollients such as jojoba oil or shea butter are added.

Cold-process soapmaking takes place at a temperature sufficiently above room temperature to ensure the liquification of the fat being used, and requires that the lye and fat be kept warm after mixing to ensure that the soap is completely saponified. A cold-process soapmaker first looks up the saponification value of the fats being used on a saponification chart, which is then used to calculate the appropriate amount of lye. Excess unreacted lye in the soap will result in a very high pH and can burn or irritate skin. Not enough lye, and the soap is greasy. Most soap makers formulate their recipes with a 4-10% discount of lye so that all of the lye is reacted and that excess fat is left for skin conditioning benefits. The lye is dissolved in water. Then oils are heated, or melted if they are solid at room temperature. Once both substances have cooled to approximately 100-110° F (37-43° C), and are no more than 10° F (~5.5° C) apart, they may be combined. This lye-fat mixture is stirred until "trace" (modern-day amateur soapmakers often use a stick blender to speed this process). Essential oils, fragrance oils, botanicals, herbs, oatmeal or other additives are added at light trace, just as the mixture starts to thicken. The batch is then poured into molds, kept warm with towels or blankets, and left to continue saponification for 18 to 48 hours. Milk soaps are the exception. They do not require insulation. Insulation may cause the milk to burn. During this time, it is normal for the soap to go through a "gel phase" where the opaque soap will turn somewhat transparent for several hours before turning opaque again. The soap will continue to give off heat for many hours after trace. After the insulation period the soap is firm enough to be removed from the mold and cut into bars. At this time, it is safe to use the soap since saponification is complete. However, cold-process soaps are typically cured and hardened on a drying rack for 2-6 weeks (depending on initial water content) before use.


In the hot-process method, lye and fat are boiled together at 80–100 °C until saponification occurs, which the soapmaker can determine by taste (the bright, distinctive taste of lye disappears once all the lye is saponified) or by eye (the experienced eye can tell when gel stage and full saponification have occurred). After saponification has occurred, the soap is sometimes precipitated from the solution by adding salt, and the excess liquid drained off. The hot, soft soap is then spooned into a mold.

The common process of purifying soap involves removal of sodium chloride, sodium hydroxide, and glycerol. These components are removed by boiling the crude soap curds in water and re-precipitating the soap with salt.

Most of the water is then removed from the soap. This was traditionally done on a chill roll which produced the soap flakes commonly used in the 1940s and 1950s. This process was superseded by spray dryers and then by vacuum dryers.

The dry soap (approximately 6-12% moisture) is then compacted into small pellets. These pellets are now ready for soap finishing, the process of converting raw soap pellets into a salable product, usually bars. It is the soap base.

Soap pellets are combined with fragrances and other materials and blended to homogeneity in an amalgamator (mixer). The mass is then discharged from the mixer into a refiner which, by means of an auger, forces the soap through a fine wire screen. From the refiner the soap passes over a roller mill (French milling or hard milling) in a manner similar to calendering paper or plastic or to making chocolate liquor. The soap is then passed through one or more additional refiners to further plasticize the soap mass. Immediately before extrusion it passes through a vacuum chamber to remove any entrapped air. It is then extruded into a long log or blank, cut to convenient lengths, passed through a metal detector and then stamped into shape in refrigerated tools. The pressed bars are packaged in many ways.

Sand or pumice may be added to produce a scouring soap for an exfoliating soap.

"Triple milled" or "french milled" soap involves a process called rebatching, or hand milling. It is a soapmaking technique used by hobbyists and artisan soapmakers. In rebatching, commercially purchased or previously made soap (a soap base) is shredded or diced finely. They begin with a soap mixture which is pressed between sets of rollers which flatten it into paper thin sheets. The sheets of soap are then shredded and ground through the rollers again. That product is then put through extrusion machinery which squeezes out a long bar of tightly compacted soap which is cut into individual bars. French Milled relates to the use of stainless steel rollers to smooth out the soap and further mix it, giving it a smoother finish and softer feel. It is milled/formed under pressure (not heat), and milled/formed and milled/formed three times. Soapmakers frequently use rebatching as a way of adding substances that could not withstand the high temperatures or caustic chemical environment of hot process soapmaking, such as certain essential oils (for example, those with a very low flash point). It makes for a finer textured soap.

The choice of liquid affects the character of the finished soap; milk is frequently used to give the soap a smooth, creamy consistency.

Mass-produced soap also typically contains chemicals, such as sodium chloride, which facilitate a longer shelf life and others which allow the mixture to efficiently process through the rollers during the manufacturing process. Any attempt to “mill” a natural soap product would fail because, being full of highly saturated fats and oils, no additives and an excess of glycerin, it would stick to the rollers.

A natural by-product of the soap-making process is glycerin. Glycerin is an humectant, which means it draws moisture to the skin. Most soap manufacturers remove the glycerin and use it in other products to increase their profit margin. The end result being, you are cleansing your skin with basically detergent.

Essential oils made from plant extracts can be added, superfatting - the addition of lovely avocado oil, almond oil or beeswax, to protect, moisten and soften the skin, and triple milling - which assures blended consistency.

My sources were Wikipedia, Pioneerlinens.com/bronnley, WikiAnswers

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