The modern definition of soap is a salt of a fatty acid, either saturated or unsaturated, which contains at least eight carbon atoms in the hydrocarbonchain. Such soaps can consist of a single fatty acid saltor a mixture of such salts .The application of soap in cleaning is necessary because it eliminates contaminants that cannot be completely removed by water alone. Soap is mainly used for cleansing, by solubilizing the insoluble contaminants of dirt, grease, and oil in water, thus allowing them to be washed away. This works because soap is a surfactant –a substance that lowers the surface tension between the water-oil interface. The insoluble contaminant is removed by associating with soap-based micelle sin solution, spheres formed by soap molecules with hydrophilic (water-attracting) heads and lipophilic (fat-attracting) tails, which encase it and make it soluble in water.These contaminants are then removed with the water once they are solubilized.Soap is also a detergent, which is defined as a surfactant, or a mixture containing one or more surfactants, having cleaning properties in dilute solutions (1). However, detergents in general are a much broader class of cleansing agents than soap. Most modern detergents are usually alkyl benzene-sulfonates, which are a family of compounds similar to soap but have the advantage of being more soluble in hard water than soap. Because of their reduced sensitivity to water hardness relative to soap, synthetic detergents have overtaken soaps as the cleansing substance of choice in the modern era because they do not interact adversely with the metal ions in hard water.However, such modern detergents are a relatively recent innovation and thus traditional soap has dominated the history of such detergents.
Origins of Soap
Investigation of the etymology of the word soap could potentially provide some indication of its historical development. The word soap originates from the Proto-Indo-European root *seib, meaning to pour out, drip. The romance language words for soap are from the late Latin sapo, mentioned in the writings of Pliny, which is a Germanic loan-word. Keeping in mind that in many languages the pronunciation of certain letters is interchangeable, translations of the word soap are quite similar and are cognates of one another. Ezov, the classical Hebrew name for a plant used for ritualistic cleansing in the Bible, translates to hyssopin. A connection could be made between the plant used for cleansing purposes and soap, which has the identical consonants as hyssop. In more ancient civilizations, the concept of soap was not always recognized with its own distinct word. For example, the Sumerians had no specific word for soap, however the same Sumerian cuneiform symbols is used for the calamus plant (a type of soap plant), for potash, and for the idea of washing. A word corresponding with the hieroglyphic anzir has been found in Demotic papyri, which may translate to soap. Also, the similar Coptic word anchir is generally translated as soap. Demotic corresponds to the period of Egyptian language 8thcentury BCE –5thcentury CE, which was preceded by the Late Egyptian period (14th–8thcentury BCE) (29). The Coptic language developed from the Demotic and Greek systems, and was utilized from the 3rd–12thcentury CE, and is still in use today in the Coptic Church (30). However, the validity of the translations for Demotic and Coptic is disputed (31). The word detergent is much more recent in origin, from the Latin detergere, meaning to wipe away or cleanse, and its usage dates to the 17thcentury CE. Although there is some etymological evidence that can be interpreted as reference to soap in the Egyptian hieroglyphs, Sumerian cuneiform symbols, and from its Proto-Indo-European origins, the etymology of the word soap does not support any civilization as the cradle of its invention. Rather, it can only be concluded that these civilizations may have been familiar with the substance. The central issue with determining the origins of soap is that, unlike with other forms of chemical technologies such as glass or ceramics, there are no significant examples of soap that survive intact to modern-day. In addition, the detection of soap as a part of archaeological studies is complicated by the fact that organic residues can undergo saponification through exposure to basic media over the millennia between their genesis and any modern analysis. As such, almost all reliable knowledge of the development of soap must come fromwritten historical records.
Soap in Mesopotamia
Mesopotamia is a geographical region in the Near East, referring to the land lying between the Euphrates and Tigris rivers. The name is based on a term local to the area, given in the time of Alexander the Great (326–323BCE),which corresponds to modern-day Iraq, and to a lesser extent Kuwait, Iran, Turkey, and Syria (Figure 5). The ancient city-states of Mesopotamia, and the civilizations that spawned them, are among the earliest known non-nomadic agrarian societies. Mesopotamia included Sumer, as well as the Akkadian, Babylonian and Assyrian empires(4th–1stmillennia BCE). Of the ancient civilizations, it is the Mesopotamians that have had a large volume of their records survived to the modern day, because they wrote on the durable writing material of clay tablets, their primary form of record keeping (34). These texts provide a rich record of their daily life, including their accounts and usage of soap.Many peoples of the ancient Near East dedicated a great deal of attention to the concept of cleanliness. In an almanac from the Mesopotamian settlement of Assur, a man is cautioned not to enter a laundry,and thus cleanse his garments or himself, on the sixth and seventh days of the month of Teshrit, this being in a month of penance. Simple detergents that were commonly used in ancient Mesopotamia to cleanse were alkalis, clays, earths, and resins, although the alkalis, such as those leached from the ashes of plants, were most common. A Sumerian tablet found in the Hittite capital of Boghazkoi discusses the use of soda for cleansing the body: With water I bathed myself. With soda I cleansed myself. With soda from a shiny basin I purified myself. With pure oil from the basin I beautified myself. With the dress of heavenly kingship I clothed myself. A variety of plants were used for their alkaline substances in Mesopotamia. In an Akkadian text belonging to a private citizen during the reign of Ashurbanipal (7thcentury BCE), the author discusses using tamarisk, date palm, pine cone and the mastakalplant (which is unidentified) for their detersive properties: May the tamarisk, whereof the tops grow high, cleanse me; may the date palm, which faces every wind, free me; may the mastakal plant,
The oldest known medical writing containing soap is a Sumerian pharm-acological tablet (2200BCE) from Nippur. A series of fifteen prescriptions are given, but the ailments to be treatedare not specified.In two of these, one is directed to wash the ailing organ with a specially prepared solution, followed by rubbing with oil. The final step involves covering the area with a substance that has been interpreted by some to be burnt plant ashes. In effect, producing a recipe for medicated soap.The first of these prescriptions gives instructions for the formation of the remedy: Sift and knead together –all in one –turtle shell, the sprouting of naga-plant (a plant used to obtain soda and other alkalies), salt, (and) mustard; wash (the sick spot) with quality beer (and) hot water; scrub (the sick spot) with all of it (the kneaded mixture); after scrubbing, rub with vegetable oil (and) cover (?) with pulverized fir.
The second prescription uses different ingredients, but also gives instructions that involve the components of soap: Pour water over a dried and pulverized water snake, the amamashumkaspal-plant, the roots of the “thorn”-plant, pulverized naga, powdered fir turpentine, (and) the feces of the garib(?)-bat; heat (the infusion), (and) wash (the sick spot) with this liquid; after washing with the liquid, rub with vegetable oil and cover with shaki. Although little direction is given as to what part of the body this remedy was supposed to cure, this set of prescriptions was preceded by the passage directing arrangement of rushes over the hands and feet of the sick man, so it is possible it was to be applied in the same area . As the first recipe includes salt, this could suggest that “salting out” was practised in antiquity, although there is no direct evidence of such. The process of salting out involves the precipitation of soap from the solution of glycerin, excess water, and impurities, thus making a hard soap. This is typically accomplished by adding salt (e.g.NaCl) to the soap solution, rendering the soap insoluble because of the large amount of electrolyte in solution. Otherwise, without filtration, the soap produced would most likely be soft and liquid in consistency because of the impurities. Also, from the recipes above, and other medical writings, it is quite possible that the Sumerians were familiar with resin soaps ( compounds of soda or potash combined with coniferous resins i.e. pulverized fir/tree sap).
Soap and Cleaning in Greece and Rome
While the Greeks and Romans had high standards of cleanliness, soap did not play a role in personal hygiene. The Greeks would pour water over themselves and perform ritualized communal bathing in public baths. The Romans took personal cleanliness to a high art, bathing in the thermæ (public baths) located all across the Roman Empire in pools of waist-high water of different temperatures. The strigil, a body scraper employed to remove perspiration, dirt, and oil that was applied before bathing, was especially used by Greek and Roman male athletes. In Homer’s The Odyssey(~800 BCE) only water is used to wash the nuptial garments of Nausica, daughter of the King of the Phaeacians. In contrast, the comic playwright Aristophanes (445 –386 BCE) mentions adulterated soda-lye being used with the Cimolian earth for washing. This “adulterated soda-lye”, depending on translation, could possibly have been causticized alkali . More specific references to soap were made by the physician Dioskourides (40 –90 CE) who wrote that the best soapwas made from natron and Cimolian earth . Pliny the Elder (23 –79 CE), the Roman natural philosopher, writes in his Naturalis Historia: "Prodest et sapo, Galliarum hoc inventum rutilandis capillis. Fit ex sebo et cinere, optimus fagino et caprino, duobus modis, spissus ac liquidus, uterque apud Germanos maiore in usu viris quam feminis. " Which translates to: Soap, too, is very useful for this purpose, an invention of the Gauls for giving a reddish tint to the hair. This substance is prepared from tallow and ashes, the best ashes for the purpose being those of the beech and yoke-elm: there are two kinds of it, the hard soap and the liquid, both of them much used by the people of Germany, the men, in particular, more than the women.
The earliest written records of soap-making date to 2200BCE in Mesopotamia . However, because saponification can occur by the simple combination of fat and plant-ash, it is highly likely that soap was made, whether intentionally or not, before this time. The slightly complicated process of rendering the fats and oils and combining it with alkali could not have been developed spontaneously. There must have been a series of steps or procedures that slowly evolved, where each step resulted in a process useful enough to be adopted in its own right. One proposed sequence of development is that people used sand or ashes to remove the grease from skin. If they rinsed the ashes off with water, the water and their skin would become slippery, which was because of the dissolved alkali salts. This water would clean better because the dissolved alkali reacts with the grease, converting it into soap. The more grease that was dissolved in the solution, the better it cleans because more soap is formed. At some point the ashes were discarded and the solution from leached ashes or concentrated alkali salts were used. In the Mesopotamian period, soap was primarily made from oil and plant ash. The Mesopotamians used it mainly for medical purposes, but also for cleansing. The Egyptians did not identify soap as such, but it is possible that they were familiar with it, through the combination of alkali and animal fat. There is evidence of soap residue being found in ancient Egyptian artefacts, but it cannot be definitively concluded that this was not the result of slow degradation of the original material. The Greco-Roman world was familiar with soap and soap making, using it for medical, textile, and beautification purposes, but not for personal hygiene. There is also archaeological evidence that soap was used in various Roman painting techniques. It is also quite probable that soap production was occurring in other parts of the world and other civilizations during this time, but no evidence has yet been found to confirm it. Soap production in antiquity was most likely a small craft industry, especially in the Mesopotamian and Egyptian periods, where locally available materials were used in its formation. However, the large expanse of the Roman empire allowed for the movement of materials and processes, one of which was soap that was imported from the Gauls. It is possible that there was some sort of soap-works preserved in Pompeii. The term saponarius (soap-maker/soap-boiler) is mentioned in 4thcentury CE writings, so there was obviously some sort of recognized profession or industry at this time. Soap was known for its medicinal purposes by Arabian physicians Rhases and Serapion the Younger in the 10th and 12th centuries CE. A small soap industry started in Marseilles in the 9th century, and Venice and England in the 14thcentury . These industries expanded, but it really wasn’t until the Industrial Revolution in the 18thand 19thcenturies that large-scale production of soap was undertaken.