Soaps and Detergents

For other uses, see Soaps and Detergents (disambiguation).

A collection of decorative soaps typically found in hotel rooms.

File:A bar of soap.jpg

Soap most commonly appears in bar form. This particular bar has seen some use and has lost its "bar" shape.

A detergent is a chemical compound or mixture of compounds used as a cleaning agent. A soap is a cleaning agent that is composed of one or more salts of fatty acids. In this sense, detergent is an umbrella term that includes soaps and other cleaning agents that differ in chemical composition. Even plain water, when used for cleaning, may be called a detergent.

There are, however, alternate ways in which the terms detergent and soap are used. For instance, the word detergent is often used when referring to synthetic cleaning agents that are not soaps (that is, not salts of fatty acids). Also, the word soap is applied to cleaning materials (such as "laundry soap") that do not contain salts of fatty acids. Most kinds of "soap" in use today are actually synthetic detergents, which are less expensive, more effective, and easier to manufacture.

• While effort has been made to reduce their negative effect upon the environment, the results have been mixed.

The term is often used to differentiate between soap and other chemical surfactants used for cleaning purposes. Sometimes the word "detergent" is used in distinction to "soap."

Soap is a surfactant used in conjunction with water for washing and cleaning.

Terminology for soaps and detergents

For a while during the infancy of other surfactants as commercial detergent products, the term "syndet," short for "synthetic detergent" was promoted to indicate this, but never caught on very well, and is incorrect in any event because soap is itself synthesized via saponification of glycerides. The term "soapless soap" also saw a brief vogue. Unfortunately there is no accurate term for detergents not made of soap other than "soapless detergent" or "non-soap detergent."

Also, the term "detergent" is sometimes used for surfactants in general, even when they are not used for cleaning. As can be seen above, this too is terminology that should be avoided as long as the term "surfactant" itself is available.

Probably the most widely used detergents other than water are soaps or mixtures composed chiefly of soaps. However, not all soaps have significant detergency.

History

Early History

Soapnut (Reeta/Sapindus) tree.

The earliest known use of a natural, soap-like material was the powder of nuts from the Reeta (Sapindus) tree, a powder used by Indians since antiquity. In accordance with Ayurvedic teachings, Hindus in India were obliged to bathe at least once a day, every morning.

The Babylonians used clay cylinders containing a soap-like substance, dating from 2800 B.C.E. A formula for soap—consisting of water, alkali, and cassia oil—was written on a Babylonian clay tablet around 2200 B.C.E.

The Ebers papyrus (Egypt, 1550 B.C.E.) indicates that ancient Egyptians bathed regularly and combined animal and vegetable oils with alkaline salts to create a soap-like substance. Egyptian documents mention that a soap-like substance was used in the preparation of wool for weaving.

Roman History

It has been reported that a factory producing soap-like substances was found in the ruins of Pompeii (CE 79). However, this report appears to be a misinterpretation of the survival of some soapy mineral substance, probably soapstone, at the Fullonica where it was used for dressing recently cleansed textiles. The ancient Romans were generally ignorant of soap's detergent properties and made use of the strigil to scrape dirt and sweat from the body.

The word "soap" (Latin sapo) appears first in a European language in Pliny the Elder's Historia Naturalis, which discusses the manufacture of soap from tallow and ashes, but the only use he mentions for it is as a pomade for hair. He mentions rather disapprovingly that among the Gauls and Germans, men are likelier to use it than women.

According to one legend, "soap" takes its name from a "Mount Sapo" where ancient Romans sacrificed animals. Rain would send a mix of animal tallow and wood ash down the mountain and into the clay soil on the banks of the Tiber. Eventually, women noticed that it was easier to clean clothes with this "soap." The location of Mount Sapo is unknown, as is the source of the "ancient Roman legend" to which this tale is typically credited.

In fact, the Latin word sapo simply means "soap." Borrowed from a Celtic or Germanic language, the term is cognate with the Latin term sebum (meaning "tallow"), which appears in Pliny the Elder's account. Roman animal sacrifices usually burned only the bones and inedible entrails of the sacrificed animals; edible meat and fat from the sacrifices were taken by humans. Under such circumstances, animal sacrifices would not have included enough fat to make much soap. The legend about Mount Sapo is probably apocryphal.

Muslim History

True soaps made from vegetable oils (such as olive oil), aromatic oils (such as thyme oil), and lye (al-Soda al-Kawia, or sodium hydroxide), were first produced by Muslim chemists in the medieval Islamic world. From the beginning of the seventh century, soap was produced in Nablus (West Bank, Palestine), Kufa (Iraq) and Basra (Iraq). Soaps as we know them today are descendants of historical Arabian soaps.

Arabian soaps were perfumed and colored; some were liquid, others were hard. The Arabs also had special soap for shaving. It was commercially sold for 3 Dirhams (0.3 Dinars) a piece in CE 981. The Persian chemist Al-Razi wrote a manuscript on recipes for true soap. A recently discovered manuscript from the thirteenth century details more recipes for soap making. One recipe recommends taking some sesame oil, a sprinkle of potash, alkali and some lime, mixing them together, and boiling. When cooked, they are poured into molds and left to set, leaving hard soap.

Historically, soap was made by mixing animal fats with lye. Because of the caustic nature of lye, this was a dangerous procedure, which could result in serious chemical burns or even blindness. Before the commercial production of lye became commonplace, it was produced at home for soap making from the ashes of a hardwood fire.

Modern History

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1922 magazine advertisement for Palmolive soap.

Castile soap, made from olive oil, was produced in Europe as early as the sixteenth century.

In modern times, the use of soap has become universal in industrialized nations due to a better understanding of the role of hygiene in reducing the population size of pathogenic microorganisms. Manufactured bar soaps first became available in the late nineteenth century, and advertising campaigns in Europe and the United States helped to increase popular awareness of the relationship between cleanliness and health. By the 1950s, soap had gained public acceptance as an instrument of personal hygiene.

A bar of blue-white offenbach soap.

Commercial soap production

Until the Industrial Revolution, soap-making was done on a small scale and the product was rough. In 1789, Andrew Pears started making a high-quality, transparent soap in London. He and his grandson, Francis Pears, opened a factory in Isleworth in 1862. William Gossage produced low-priced, good quality soap from the 1850s. Robert Spear Hudson began manufacturing a soap powder in 1837, initially by grinding the soap with a mortar and pestle. William Hesketh Lever and his brother James bought a small soap works in Warrington in 1885 and founded what became one of the largest soap businesses, now called Unilever. These soap businesses were among the first to employ large-scale advertising campaigns to sell the output of their factories.

Forms of soap

Soap usually comes in a solid, molded form, called a bar, based on its typical shape. The use of thick liquid soap has also become widespread, especially from soap dispensers in public washrooms. When applied to a soiled surface, soapy water effectively holds particles in suspension, which can then be rinsed off with clean water.

Components of detergents and their functions

Diagram of how soap works.

As noted above, soaps are salts of fatty acids. A molecule of soap may be represented as follows:

(fatty end) :CH₃-(CH₂)_n - COO⁻Na⁺: (water soluble end)

Thus, each molecule of soap has (a) an ionic end, which is hydrophilic (water-attracting) and soluble in water; and (b) a nonpolar hydrocarbon chain that is hydrophobic (water-repelling) that can attach to nonpolar materials such as grease and oil. Likewise, detergents in general contain molecules with hydrophilic and hydrophobic ends. (In nonionic detergents, the hydrophilic nature is conferred by the presence of special functional groups such as hydroxyl groups.) These molecules form bridges between water and oil, breaking up the oil and forming an emulsion consisting of oil droplets suspended in water. As a result, the oil and associated dirt particles become solubilized and can be rinsed away with clean water.

Detergent molecules come in two forms: straight and branched. This difference affects sudsing but not cleansing ability. Suds produced by straight molecules of detergent break down quickly; suds produced by branched molecules break down slowly, if at all.

A key ingredient in both solid and liquid laundry detergents is a surfactant. A surfactant is a substance that, when added to water, significantly reduces the surface tension of the water. This effect allows water to wash surfaces better. There are many different types of organic compounds which can function as surfactants. Surfactants are thick, viscous liquids; however, some are soft, waxy or greasy solids.

Surfactants typically have somewhat longer molecules which may or may not have an electric charge. Surfactants with uncharged molecules are non-ionic surfactants. Surfactants with positively charged molecules (or ions) are cationic surfactants. Surfactants with negatively charged molecules (or ions) are anionic surfactants. Surfactants with both positively and negatively charged part in the same molecule are zwitterionic surfactants. Most brands of laundry detergent have anionic or nonionic surfactants or a mixture of the two, although cationic surfactants have been used in laundry detergents. The use of cationic and anionic surfactants together is incompatible in the same detergent. The usual content of surfactants in a typical detergent is about 8-18%.

Detergents, especially those made for use with water, are mixtures of various components that serve different functions. A given detergent may contain several of the following components:

• Surfactants, which 'cut' grease from surfaces.
• Abrasives that scour the surfaces.
• Substances that modify pH or affect performance or stability of other ingredients—for example, acids for descaling, or caustics to destroy dirt.
• Water softeners counteract the effect of "hardness" ions in other components.
• Oxidizing agents (oxidizers) that bleach surfaces and destroy dirt.
• Non-surfactant materials that keep dirt in suspension.
• Enzymes to digest proteins, fats, or carbohydrates in dirt or to modify fabric feel.
• Ingredients that modify the foaming properties of the cleaning surfactants, to either stabilize or counteract foam.
• Additional ingredients, such as optical brighteners, softeners, colors, and perfumes.

The material to be cleaned dictates the composition of the detergent that should be used and the apparatus to be used. For instance, the following are examples of different glass-cleaning agents that are appropriate for different contexts:

• A chromic acid solution is used to get glass very clean for precision-demanding purposes, such as analytical chemistry
• A high-foaming mixture of surfactants with low skin irritation is needed for hand washing of drinking glasses in a sink or dishpan.
• Any of various non-foaming compositions are used for glasses in a dishwashing machine.
• An ammonia-containing solution is useful for cleaning windows, with no need for rinsing.
• Windshield washer fluid is useful especially when a vehicle is in motion.

In powdered or granular solid detergents, the surfactant is soaked into the solid ingredients. In liquid laundry detergents, liquid or even solid surfactant are blended into the liquid detergent. There is usually a limit on how much liquid surfactant can soak into powder or granular solids solid detergent mushy. More liquid surfactant can usually be blended into a liquid detergent. The liquid detergents commonly contain at least some water to help liquefy the other additives and still have the detergent pour able. The liquid detergents may also have other solvent liquids, such as alcohol or a hydrotrope, to help blend all the additives together.

Laundry detergents may have ingredients to help control the pH of the wash water. For example, solid detergents usually contain sodium carbonate (soda ash) or sodium bicarbonate to maintain pH by neutralizing any acidic materials that may enter the wash water.

Compounds called "builders" are often used to enhance ("build") the surfactant effect. Their role is to lower the water hardness by scavenging the calcium and magnesium ions and adsorbing them or chelating them. Some form of sodium phosphate can be used here, such as trisodium orthophosphate, monosodium orthophosphate, or a form of tripolyphosphate (TPP). In some locations, phosphate is no longer used as an additive due to environmental concerns as phosphates in surface waters stimulate algal bloom. As alternatives, other chelating agents are used. Sodium carbonate precipitates insoluble calcium carbonate and magnesium carbonate. Organic chemicals similar to EDTA can be employed, eg. nitriloacetic acid (NTA). Borates can be used as well. Ion exchange materials are frequently used in modern formulations; the most common kind is based on synthetic zeolites, often with polycarboxylate based polyelectrolytes. The usual content of such materials in a typical detergent is about 20-45%.

Many detergents contain bleaches. In North American countries, sodium hypochlorite based bleach additives are more common. These work at lower temperatures and do not need activation. In Europe, peroxide-based bleaches are prevalent instead. The chemicals employed are usually sodium percarbonate and sodium perborate, or other compounds that release hydrogen peroxide. Peroxide bleaches either need higher temperature (60 °C or more) to become effective, or a suitable catalyst or activator (eg. manganese or iron complexes, or TAED) which lowers the required temperature down to 40 °C or even to room temperature. The usual content of bleaches in a typical detergent is about 15-30%. It is possible to overdo the bleaching; the Persil Power fiasco is a good example of deployment of too powerful bleaching activator.

The detergents promising making the laundry "whiter than white" usually contain optical brighteners, acting as phosphors converting some ultraviolet radiation to blue light and optically offsetting the yellowing of the material. The usual content of optical brighteners in a typical detergent is about 0.1%.

Fillers are a bulk component in many detergents. Their primary role is modifying the physical properties of the material. In solid detergents, sodium sulfate or borax can be used to make the powder free-flowing. In liquid detergents alcohols are added to increase the solubility of the compounds and to lower the mixture's freezing point. Corrosion inhibitors can be added to prolong the lifetime of the washing machines; sodium silicate can be used here. Anti-foaming agents are added to lower the production of foam and to make the presence of detergents in wastewater less obvious. The usual content of fillers in a typical detergent is about 5-45%.

Some laundry detergents have enzymes to help in removal of biological stains (eg. grass or blood), often enzymes produced by the bacteria Bacillus subtilis and Bacillus licheniformis. The content of enzymes can reach up to 0.75%.

Some laundry detergents have fabric softeners. Perfume or color ingredients are sometimes added for better smell or to give a detergent some color.

Other brands, however, are left without these additives, marketed to those who avoid these because of allergies or individual preference. There are also detergents made with vegetable-based surfactants which are popular in health food stores.

Soapmaking

Handmade soaps sold at a shop in Hyères, France

The most popular soapmaking processes 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. While some people think that this is not really soap-making, the Hand Crafted Soap Makers Guild does recognize this as a legitimate form of soap making or soap crafting. Some soapers also practice other processes, such as the historical hot process, and make special soaps such as clear soap (glycerin soap), which must be made through the melt and pour process.

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. 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 'at trace' (the point at which the saponification process is sufficiently advanced that the soap has begun to thicken), after most of the oils have saponified, so that they remain unreacted in the finished soap. Superfatting can also be accomplished through a processed called superfat discount, where, instead of putting in extra fats, the soap maker puts in less lye.

Lye

Reacting fat with sodium hydroxide will produce a hard soap.

Reacting fat with potassium hydroxide will produce a soap that is either soft or liquid. Historically, the alkali used was potassium hydroxide made from the deliberate burning of vegetation such as bracken, or from wood ashes.

Fat

Handicraft made Marseille soap

Soap is derived from either oils or fats. Sodium tallowate, a common ingredient in many soaps, is in fact derived from rendered beef fat. Soap can also be made of vegetable oils, such as palm oil, and the product is typically softer. If soap is made from pure olive oil it may be called Castile soap or Marseille soap. Castile is also sometimes applied to soaps with a mix of oils, but a high percentage of olive oil.

An array of quality oils and butters are used in the process such as olive, coconut, palm, cocoa butter, hemp oil and shea butter to list a few. Each oil chosen by the soap maker has unique characteristics that provide different qualities to handmade soaps including mildness, lathering and hardness. For example olive oil provides mildness in soap; coconut oil provides lots of lather while coconut and palm oils provides hardness. Most common, though, is a combination of coconut, palm, and olive oils.

Process

In both cold-process and hot-process soapmaking, heat may be required for saponification.

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.

Unlike cold-processed soap, hot-processed soap can be used right away because lye and fat saponify more quickly at the higher temperatures used in hot-process soapmaking.

Hot-process was used when the purity of lye was unreliable, and can use natural lye solutions such as potash. The main benefit of hot processing is that the exact concentration of the lye solution does not need to be known to perform the process with adequate success.

Cold-process requires exact measurement of lye to fat using saponification charts to ensure that the finished product is mild and skin friendly. Saponification charts can also be used in hot-process soapmaking, but are not as necessary as in cold-process.

Hot process

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.

Cold process

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 and oily. 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 degrees Fahrenheit, and are no more than 10 degrees Fahrenheit apart in temperature, 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.). There are varying levels of trace. Depending on how your additives will affect trace, they may be added at light trace, medium trace or heavy trace. After much stirring, the mixture turns to the consistency of a thin pudding.

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. If using caustic soda it is recommended that the soap is left to cure for at least 4 weeks.

Purification and finishing

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.

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. This process is most common in creating soaps used for human hygiene. The scouring agents serve to remove dead skin cells from the surface being cleaned. This process is called exfoliation. Many newer materials are used for exfoliating soaps which are effective but do not have the sharp edges and poor size distribution of pumice.

Soap manufacture

Many soaps are mixtures of sodium (soda) or potassium (potash) salts of fatty acids. They can be prepared by reacting oils or fats with an alkali (such as sodium or potassium hydroxide) at 80–100 °C. The process is known as saponification. The fats are hydrolyzed by the base, yielding glycerol and crude soap. Historically, the alkali used was potassium hydroxide made from the deliberate burning of vegetation such as bracken, or from wood ashes.

A common ingredient in many soaps is sodium tallowate, which is derived from rendered beef fat. Soap can also be made from vegetable oils, such as olive oil. Soap made entirely (or mostly) from olive oil is called castile soap.

Soap purification and finishing

The common process of purifying soap involves removal of sodium chloride, sodium hydroxide, and glycerol. These impurities 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. Soap finishing is the process of converting raw soap pellets into salable product, usually bars.

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. This process is most common in creating soaps used for human hygiene. The scouring agents serve to remove dead skin cells from the surface being cleaned. This process is called exfoliation. Many newer materials are used for exfoliating soaps which are effective but do not have the sharp edges and pore size distribution of pumice.

Handmade soap

File:Handmade soap.jpg

Handmade soap.

Some individuals continue to make soap in the home. The traditional name "soaper," for a soapmaker, is still used by those who make soap as a hobby. Those who make their own soaps are also known as soapcrafters.

The most popular soapmaking processes 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, but this is not really to be considered soap-making. Some soapers also practice other processes, such as the historical hot process, and make special soaps such as clear soap (aka glycerin soap).

Handmade soap differs from industrial soap in that, usually, an excess of fat is used to consume the alkali (superfatting), and in that the glycerin is not removed. 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 'at trace' (the point at which the saponification process is sufficiently advanced that the soap has begun to thicken), after most of the oils have saponified, so that they remain unreacted in the finished soap.

Disadvantages

Today, fat-based soaps have mostly been superseded by modern detergents. Washing agents do not contain soap for cleaning fabric, but for reducing foam.

The disadvantages of commercial soaps are:

• Due to the fact that most commercial soaps eliminate the glycerine from soaps to use in other industires, this deprives the skin of the natural, moisturising glycerine and generally leaves the skin feeling dry.
• Some antibacterial soaps have chemicals killing bacteria that coexist on the skin's surface and are essential to skin health. More alarmingly, the rise of antibacterial soaps contributes to antibiotic resistant bacteria. ^{[citation needed]}
• Soap-based products often contain the additive sodium laureth sulfate, which research has found to be harsh on skin. This product is also present in many non-soap cleaners for personal hygiene (shampoos, bathfoams, toothpaste, etc.).
• Soap can react mildly basically with fabrics resulting in damage over the long term. This is usually due to excess sodium hydroxide (NaOH, an alkali/base) left from manufacture, but can also be caused by the very slight presence of NaOH from the equilibrium reaction:
  R-COO-Na + H₂O ↔ R-COO^- + Na⁺ + H₂O ↔ R-COOH + NaOH
  However, this equilibrium strongly favors the left-hand side so the fraction of NaOH formed is minuscule
• Soap reacts with lime to form an insoluble deposit (soap scum) in "hard water":
  2Na⁺(R-COO)^-_(aq) + Ca²⁺(HCO₃^-)_2(aq) → 2Na⁺(HCO₃)^-_(aq) + Ca(R-COO)_2(s) - where R stands for an alkyl group (precipitate)
• A wide variety of emollient materials, such as shea or cocoa butters, are substantive to the skin.
• Poorly finished soaps contain alkali (NaOH) and react mildly basically with skin and fabric; commercial products are finished to neutrality or to a weak acid content to prevent this and be more compatible with the skin's slightly acidic pH.
• Commercial products use chelating molecules (sequestrants), often EDTA derivatives to bind with any free Ca or Mg ions and prevent soap scum. These also help reduce fragrance loss, discolouration and rancidity.
• Castile soap has a very high alkalinity level, measured at about 9. pH of skin and hair has a slightly acidic pH level known to be about 5 to 6. Due to the high pH level, liquid castile soap is usually not recommended by soapmakers who market this high pH soap for washing hair because it is not pH-balanced and it may cause hair to become dry.

Environmental concerns

In the 1960s, detergent manufacturers waged an advertising battle over who had the longest lasting suds, and detergent compounds quickly appeared in the waterways. Suds began to appear in streams, rivers, lakes, and at the foot of Niagara Falls, piles of discolored detergent foam rose eight feet high.

Detergents also contain phosphate additives to soften the water and thereby improve the effectiveness of the detergent molecules. It was noted that between 1940 and 1970 the amount of phosphates in city wastewater increased from 20,000 to 150,000 tons per year.

With the increase in phosphates, algal blooms grew splendidly on the excess phosphorus and consumed the majority of all oxygen in the waters, killing fish and plants.

Uses

File:Washingpowder.jpg

Laundry detergents are one of many possible uses of detergents.

Detergents are mainly used for washing dishes and laundering clothes and other fabrics. In addition, detergents are often added to a variety of products, to prevent the buildup of undesirable deposits. Some products that may contain detergents include:

• toothpastes
• antiseptic agents
• dry-cleaning solutions
• gasoline
• lubricating oils

A nature-friendly way of interrupting an ant trail is to pour soapy water on the trail. The soapy water destroys the scent the ants were following to get to food.

Caution

Allowing soap to sit on any surface (such as skin or clothes) over time can imbalance the moisture content on it and result in the dissolving of fabrics and dryness of skin.

Laundry detergents

Laundry detergent is a type of detergent that is added when one is washing laundry to help get the laundry cleaner. It is often colloquially called laundry soap or simply detergent or soap and it helps wash the fabric in a manner rather analogous to the way soap helps wash hands, other parts of the body, or other things cleaner than washing with water alone. Laundry detergent has traditionally been a powdered or granular solid, but the use of liquid laundry detergents has gradually increased over the years, and these days use of liquid detergent equals or even exceeds use of solid detergent. Some brands also manufacture laundry soap in tablets and dissolvable packets, so as to eliminate the need to measure soap for each load of laundry.

Use of laundry detergent

Because it is consumed when it is used, the sale of laundry detergent is a rather large business. There are many different kinds or brands of laundry detergent sold, many of them claiming some special qualities as selling points. Each brand has its own instructions on how to use it and what amount to use written on the container it comes in. Some brands of laundry detergent purport to be more concentrated and can be added in smaller amounts. The detergent can be added onto the laundry or to the wash water at the start of the wash, or it can be added beforehand or soon after starting the wash into a special compartment in a washing machine made for that purpose, to be flushed into the wash by the wash water. Often bleach is a separate additive to the wash, but there are laundry detergents which have bleach already blended in with them. The detergent is soluble in water and makes the water wash the laundry better along with agitation or tumbling. The detergent does its work and is needed during the initial "Wash" cycle to separate the dirt or soil out from the fabric. The purpose of the rinses which follow is to rinse the detergent residue from the laundry as well as to remove the dirt suspended in the wash water by replacing the initial wash water with fresh water.

Separate stain pre-treatment products are sometimes available to be added directly to stained areas of fabrics. However, undiluted liquid laundry detergent or a paste of solid detergent made by mixing in a little water may be used to pre-treat heavily soiled or stained areas of the fabric by scrubbing in the detergent prior to the wash. Removal of certain types of stains is tough and can be achieved only with varying degrees of success. Also, special oxidizer washing products have become available in liquid or solid granular form. Such solid products often contain sodium percarbonate or sodium perborate and the liquid products often contain hydrogen peroxide. They are often marketed as containing "active oxygen." Some laundry detergent is specially sold for wool fabric.

Containers and sizes

Solid laundry detergent is commonly sold in cardboard boxes and plastic tubs. In many parts of Africa, laundry detergent is also sold in single-use packets. The size of the boxes can vary from small single-use boxes sold from vending machines in laundromats to large economy-size boxes. In some cases, plastic measuring scoops have been included inside the boxes. Liquid detergent is sold in plastic bottles, usually high density polyethylene or sometimes PET or other kinds. Again, various sizes are available. On large size bottles, a handle to carry the bottle is often pre-formed as part of the bottle. The bottle caps are often made large enough so they can be used as cups for measuring out the liquid detergent.

Contents

A key ingredient in both solid and liquid laundry detergents is a surfactant. A surfactant is a substance which, when added to water, significantly reduces the surface tension of the water. This effect allows water to wash surfaces better. There are many different types of organic compounds which can function as surfactants. Most surfactants are thick, viscous liquids, but some are soft, waxy or greasy solids. Detergent Molecules consist of:

Surfactants typically have somewhat longer molecules which may or may not have an electric charge. Surfactants with uncharged molecules are non-ionic surfactants. Surfactants with positively charged molecules (or ions) are cationic surfactants. Surfactants with negatively charged molecules (or ions) are anionic surfactants. Surfactants with both positively and negatively charged part in the same molecule are zwitterionic surfactants. Most brands of laundry detergent have anionic or nonionic surfactants or a mixture of the two, although cationic surfactants have been used in laundry detergents. The use of cationic and anionic surfactants together is incompatible in the same detergent.

In powdered or granular solid detergents, the surfactant is soaked into the solid ingredients. In liquid laundry detergents, liquid or even solid surfactant are blended into the liquid detergent. There is usually a limit on how much liquid surfactant can soak into powder or granular solids before making the solid detergent mushy. More liquid surfactant can usually be blended into a liquid detergent. The liquid detergents commonly contain at least some water to help liquify the other additives and still have the detergent pourable. The liquid detergents may also have other solvent liquids, such as alcohol or a hydrotrope, to help blend all the additives together.

Laundry detergents may have ingredients to help control the pH of the wash water. For example, solid detergents usually contain sodium carbonate (soda ash) or sodium bicarbonate to maintain pH by neutralizing any acidic materials that may enter the wash water. Some other ingredients which solid detergents may have include sodium silicate or some form of sodium phosphate such as trisodium orthophosphate, monosodium orthophosphate, or a form of tripolyphosphate. In some locations, phosphate is no longer used as an additive due to environmental concerns.

Some laundry detergents have enzymes to help in stain removal. Some laundry detergents have fabric softeners. Perfume or color ingredients are sometimes added for better smell or to give a detergent some color.

Other brands, however, are left without these additives, marketed to those who avoid these because of allergies or individual preference. There are also detergents made with vegetable-based surfactants which are popular in health food stores.

See also

• Fatty acid
• Phosphate
• Potassium hydroxide
• Sodium hydroxide

References

ISBN links support NWE through referral fees

• Garzena, Patrizia - Tadiello, Marina (2004). Soap Naturally - Ingredients, methods and recipes for natural handmade soap. Programmer Publishing. ISBN 978-0975676400.

• Maine, Sandy (1995). The Soap Book: Simple Herbal Recipes. Interweave Press. ISBN 1-883010-14-4.

• Tarekh Al-Masoudi\the first book. [The Masoudi History-printed in 1989 Beirut-Lebanon]

External links

History

• Soap history by The Soap and Detergent Association
• The Discovery and Prehistory of Soap by R W Hedge at Butser Ancient Farm
• The History of Soap by C'etrange
• History of soap by the Pharmaceutical Journal
• Colonial Soap Making. Its History and Techniques. (The Soap Factory)
• Soap Naturally by Patrizia Garzena, contains a history of soap; rebuts the "Mount Sapo" legend.

Soap making

• About Candle and Soap Making - Soap making projects, instructions, recipes, suppliers and more from About.com
• Glossary for the Modern Soap Maker. Soap making terminology defined.
• Create The Dream Magazine - Magazine for Artisans of Soap, Candle, and Herbal Products.
• Creative Artisans Network.
• The Soap Making Home Page
• Handcrafted Soap Maker's Guild
• Soap Making Instructions & Recipes
• Instructions for Making Crock Pot Handmade Soap

Other

• How to Use Shaving Soap
• Removing soap scum
• Detergent compositions or components

Credits

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• Soap  ^history
• Detergent  ^history
• Laundry_detergent  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Soaps and Detergents"

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