A candle is an ignitable wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a fragrance. A candle can also provide heat, light, or a method of keeping time.
A person who makes candles is traditionally known as a chandler.[1] Various devices have been invented to hold candles, from simple tabletop candlesticks, also known as candle holders, to elaborate candelabra and chandeliers.[2]
For a candle to burn, a heat source (commonly a naked flame from a match or lighter) is used to light the candle's wick, which melts and vaporizes a small amount of fuel (the wax). Once vaporized, the fuel combines with oxygen in the atmosphere to ignite and form a constant flame. This flame provides sufficient heat to keep the candle burning via a self-sustaining chain of events: the heat of the flame melts the top of the mass of solid fuel; the liquefied fuel then moves upward through the wick via capillary action; the liquefied fuel finally vaporizes to burn within the candle's flame.
As the fuel (wax) is melted and burned, the candle becomes shorter. Portions of the wick that are not emitting vaporized fuel are consumed in the flame. The incineration of the wick limits the length of the exposed portion of the wick, thus maintaining a constant burning temperature and rate of fuel consumption. Some wicks require regular trimming with scissors (or a specialized wick trimmer), usually to about one-quarter inch (~0.7 cm), to promote slower, steady burning, and also to prevent smoking. Special candle-scissors called "snuffers" were produced for this purpose in the 20th century and were often combined with an extinguisher. In modern candles, the wick is constructed so that it curves over as it burns. This ensures that the end of the wick gets oxygen and is then consumed by fire—a self-trimming wick.[3]
Etymology
The word candle comes from Middle English candel, from Old English and from Anglo-Norman candele, both from Latin candēla, from candēre, to shine.[4]
History
Main article: History of candle making
Prior to the candle, people used oil lamps in which a lit wick rested in a container of liquid oil. Liquid oil lamps had a tendency to spill, and the wick had to be advanced by hand.[citation needed] Romans began making true dipped candles from tallow, beginning around 500 BC.[5] European candles of antiquity were made from various forms of natural fat, tallow, and wax. In Ancient Rome, candles were made of tallow due to the prohibitive cost of beeswax.[6] It is possible that they also existed in Ancient Greece, but imprecise terminology makes it difficult to determine.[6] The earliest surviving candles originated in Han China around 200 BC. These early Chinese candles were made from whale fat.
During the Middle Ages, tallow candles were most commonly used. By the 13th century, candle making had become a guild craft in England and France. The candle makers (chandlers) went from house to house making candles from the kitchen fats saved for that purpose, or made and sold their own candles from small candle shops.[7] Beeswax, compared to animal-based tallow, burned cleanly, without smoky flame. Beeswax candles were expensive, and relatively few people could afford to burn them in their homes in medieval Europe. However, they were widely used for church ceremonies.[8]
In the 18th and 19th centuries, spermaceti, a waxy substance produced by the sperm whale, was used to produce a superior candle that burned longer, brighter and gave off no offensive smell.[9] Later in the 18th century, colza oil and rapeseed oil came into use as much cheaper substitutes.
Modern era
Price's Candles became the largest candle manufacturer in the world by the end of the 19th century
The manufacture of candles became an industrialized mass market in the mid 19th century. In 1834, Joseph Morgan,[10] a pewterer from Manchester, England, patented a machine that revolutionised candle making. It allowed for continuous production of molded candles by using a cylinder with a moveable piston to eject candles as they solidified. This more efficient mechanized production produced about 1,500 candles per hour. This allowed candles to be an affordable commodity for the masses.[11] Candlemakers also began to fashion wicks out of tightly braided (rather than simply twisted) strands of cotton. This technique makes wicks curl over as they burn, maintaining the height of the wick and therefore the flame. Because much of the excess wick is incinerated, these are referred to as "self-trimming" or "self-consuming" wicks.[12]
In the mid-1850s, James Young succeeded in distilling paraffin wax from coal and oil shales at Bathgate in West Lothian and developed a commercially viable method of production.[13] Paraffin could be used to make inexpensive candles of high quality. It was a bluish-white wax, which burned cleanly and left no unpleasant odor, unlike tallow candles. By the end of the 19th century candles were made from paraffin wax and stearic acid.
By the late 19th century, Price's Candles, based in London, was the largest candle manufacturer in the world.[14] Founded by William Wilson in 1830,[15] the company pioneered the implementation of the technique of steam distillation, and was thus able to manufacture candles from a wide range of raw materials, including skin fat, bone fat, fish oil and industrial greases.
Despite advances in candle making, the candle industry declined rapidly upon the introduction of superior methods of lighting, including kerosene and lamps and the 1879 invention of the incandescent light bulb. From this point on, candles came to be marketed as more of a decorative item.
Use
See also: Ceremonial use of lights § Candles
Candle lighting in the Visoki Dečani monastery
Closeup view of candle at night
Before the invention of electric lighting, candles and oil lamps were commonly used for illumination. In areas without electricity, they are still used routinely. Until the 20th century, candles were more common in northern Europe. In southern Europe and the Mediterranean, oil lamps predominated.
In the developed world today, candles are used mainly for their aesthetic value and scent, particularly to set a soft, warm, or romantic ambiance, for emergency lighting during electrical power failures, and for religious or ritual purposes.
Other uses
With the fairly consistent and measurable burning of a candle, a common use of candles was to tell the time. The candle designed for this purpose might have time measurements, usually in hours, marked along the wax. The Song dynasty in China (960–1279) used candle clocks.[16]
By the 18th century, candle clocks were being made with weights set into the sides of the candle. As the candle melted, the weights fell off and made a noise as they fell into a bowl.
In the days leading to Christmas some people burn a candle a set amount to represent each day, as marked on the candle. The type of candle used in this way is called the Advent candle,[17] although this term is also used to refer to a candle that decorates an Advent wreath.
Components
Wax
The hydrocarbon C31H64 is a typical component of paraffin wax, from which most modern candles are produced.
Unlit candles
Candles for Christmas.
For most of recorded history candles were made from tallow (rendered from beef or mutton-fat) or beeswax. From the mid 1800s they were also made from spermaceti, a waxy substance derived from the Sperm whale, which in turn spurred demand for the substance. Candles were also made from stearin (initially manufactured from animal fats but now produced almost exclusively from palm waxes).[18][19] Today, most candles are made from paraffin wax, a product of petroleum refining.[20]
Candles can also be made from microcrystalline wax, beeswax (a byproduct of honey collection), gel (a mixture of polymer and mineral oil),[21] or some plant waxes (generally palm, carnauba, bayberry, or soybean wax).
The size of the flame and corresponding rate of burning is controlled largely by the candle wick.
Production methods utilize extrusion moulding.[20] More traditional production methods entail melting the solid fuel by the controlled application of heat. The liquid is then poured into a mould or a wick is repeatedly immersed in the liquid to create a dipped tapered candle. Often fragrance oils, essential oils or aniline-based dye is added.
Wick
Main article: Candle wick
A candle wick works by capillary action, drawing ("wicking") the melted wax or fuel up to the flame. When the liquid fuel reaches the flame, it vaporizes and combusts. The candle wick influences how the candle burns. Important characteristics of the wick include diameter, stiffness, fire-resistance, and tethering.
A candle wick is a piece of string or cord that holds the flame of a candle. Commercial wicks are made from braided cotton. The wick's capillarity determines the rate at which the melted hydrocarbon is conveyed to the flame. If the capillarity is too great, the molten wax streams down the side of the candle. Wicks are often infused with a variety of chemicals to modify their burning characteristics. For example, it is usually desirable that the wick not glow after the flame is extinguished. Typical agents are ammonium nitrate and ammonium sulfate.[20]
Characteristics
Light
A room lit by the glow of many candles
Based on measurements of a taper-type, paraffin wax candle, a modern candle typically burns at a steady rate of about 0.1 g/min, releasing heat at roughly 80 W.[22] The light produced is about 13 lumens, for a luminous efficacy of about 0.16 lumens per watt (luminous efficacy of a source) – almost a hundred times lower than an incandescent light bulb.
The luminous intensity of a typical candle is approximately one candela. The SI unit, candela, was in fact based on an older unit called the candlepower, which represented the luminous intensity emitted by a candle made to particular specifications (a "standard candle"). The modern unit is defined in a more precise and repeatable way, but was chosen such that a candle's luminous intensity is still about one candela.
Temperature
See also: Combustion
The hottest part of a candle flame is just above the very dull blue part to one side of the flame, at the base. At this point, the flame is about 1,400 °C (2,550 °F). However note that this part of the flame is very small and releases little heat energy. The blue color is due to chemiluminescence, while the visible yellow color is due to radiative emission from hot soot particles. The soot is formed through a series of complex chemical reactions, leading from the fuel molecule through molecular growth, until multi-carbon ring compounds are formed. The thermal structure of a flame is complex, hundreds of degrees over very short distances leading to extremely steep temperature gradients. On average, the flame temperature is about 1,000 °C (1,830 °F).[23] The color temperature is approximately 1000 K.
Candle flame
Five zones of a standard domestic candle flame
A candle flame is formed because wax vaporizes on burning. A candle flame is widely recognized as having between three and five regions or "zones":
Zone I - this is the non-luminous, lowest, and coolest part of the candle flame. It is located around the base of the wick where there is insufficient oxygen for fuel to burn. Temperatures are around 600 °C (1,112 °F).
Zone II - this is the blue zone which surrounds the base of the flame. Here the supply of oxygen is plentiful, and the fuel burns clean and blue. It is heat from this zone which causes the wax to melt. Temperatures are around 800 °C (1,470 °F)
Zone III - the dark zone is a region directly above the wick containing unburnt wax. Pyrolysis takes place here. Temperature is around 1,000 °C (1,830 °F)
Zone IV - the middle or luminous zone is yellow/ white and is located above the dark zone. It is the brightest zone, but not the hottest. It is an oxygen-depleted zone with insufficient oxygen to burn all of the wax vapor rising from below it resulting in only partial combustion. The zone also contains unburnt carbon vapor. Temperature is around 1,200 °C (2,190 °F).
Zone V - The non-luminous outer zone or veil surrounds Zone IV. Here the flame is at its hottest, at around 1,400 °C (2,550 °F), and complete combustion occurs. It is light blue in color though most of it is invisible.[24][25]
The main determinant of the height of a candle flame is the diameter of the wick. This is evidenced in tealights where the wick is very thin and the flame is very small. Candles whose main purpose is illumination use a much thicker wick.[26]
History of study
One of Michael Faraday's significant works was The Chemical History of a Candle, where he gives an in-depth analysis of the evolutionary development, workings and science of candles.[27]
Hazards
According to the U.S. National Fire Protection Association, candles are a leading source of residential fires in the United States with almost 10% of civilian injuries and 6% of fatalities from fire attributed to candles.[28] A candle flame that is longer than its laminar smoke point will emit soot.[29] Proper wick trimming will reduce soot emissions from most candles.
The liquid wax is hot and can cause skin burns, but the amount and temperature are generally rather limited and the burns are seldom serious. The best way to avoid getting burned from splashed wax is to use a candle snuffer instead of blowing on the flame. A candle snuffer is usually a small metal cup on the end of a long handle. Placing the snuffer over the flame cuts off the oxygen supply. Snuffers were common in the home when candles were the main source of lighting before electric lights were available. Ornate snuffers, often combined with a taper for lighting, are still found in those churches which regularly use large candles.
Glass candle-holders are sometimes cracked by thermal shock from the candle flame, particularly when the candle burns down to the end. When burning candles in glass holders or jars, users should avoid lighting candles with chipped or cracked containers, and stop use once 1/2 inch or less of wax remains.
A former worry regarding the safety of candles was that a lead core was used in the wicks to keep them upright in container candles. Without a stiff core, the wicks of a container candle could sag and drown in the deep wax pool. Concerns rose that the lead in these wicks would vaporize during the burning process, releasing lead vapors — a known health and developmental hazard. Lead core wicks have not been common since the 1970s. Today, most metal-cored wicks use zinc or a zinc alloy, which has become the industry standard. Wicks made from specially treated paper and cotton are also available.
Regulation
International markets have developed a range of standards and regulations to ensure compliance, while maintaining and improving safety, including:
Europe: GPSD, EN 15493, EN 15494, EN 15426, EN 14059, REACH, RAL-GZ 041 Candles (Germany), French Decree 91-1175
United States: ASTM F2058, ASTM F2179, ASTM F2417, ASTM F2601, ASTM F2326, California Proposition 65, CONEG
China: QB/T 2119 Basic Candle, QB/T 2902 Art Candle, QB/T 2903 Jar Candle, GB/T 22256 Jelly Candle
Accessories
Wick-trimmer
Candle holders
Decorative candleholders, especially those shaped as a pedestal, are called candlesticks; if multiple candle tapers are held, the term candelabrum is also used. The root form of chandelier is from the word for candle, but now usually refers to an electric fixture. The word chandelier is sometimes now used to describe a hanging fixture designed to hold multiple tapers.
Many candle holders use a friction-tight socket to keep the candle upright. In this case, a candle that is slightly too wide will not fit in the holder, and a candle that is slightly too narrow will wobble. Candles that are too big can be trimmed to fit with a knife; candles that are too small can be fitted with aluminium foil. Traditionally, the candle and candle holders were made in the same place, so they were appropriately sized, but international trade has combined the modern candle with existing holders, which makes the ill-fitting candle more common. This friction tight socket is only needed for the federals and the tapers. For tea light candles, there are a variety of candle holders, including small glass holders and elaborate multi-candle stands. The same is true for votives. Wall sconces are available for tea light and votive candles. For pillar-type candles, the assortment of candle holders is broad. A fireproof plate, such as a glass plate or small mirror, is a candle holder for a pillar-style candle. A pedestal of any kind, with the appropriate-sized fireproof top, is another option. A large glass bowl with a large flat bottom and tall mostly vertical curved sides is called a hurricane. The pillar-style candle is placed at the bottom center of the hurricane. A hurricane on a pedestal is sometimes sold as a unit.
A bobèche is a drip-catching ring, which may also be affixed to a candle holder, or used independently of one. Bobèches can range from ornate metal or glass, to simple plastic, cardboard, or wax paper. Use of paper or plastic bobèches is common at events where candles are distributed to a crowd or audience, such as Christmas carolers or people at other concerts/festivals.
Candle followers
These are glass or metal tubes with an internal stricture partway along, which sit around the top of a lit candle. As the candle burns, the wax melts and the follower holds the melted wax in, whilst the stricture rests on the topmost solid portion of wax. Candle followers are often deliberately heavy or weighted to ensure they move down as the candle burns lower, maintaining a seal and preventing wax escape. The purpose of a candle follower is threefold:
To contain the melted wax, making the candle more efficient, avoiding mess, and producing a more even burn.
As a decoration, either due to the ornate nature of the device, or (in the case of a glass follower) through light dispersion or colouration.
If necessary, to shield the flame from wind.
Candle followers are often found in churches on altar candles.
Candle snuffers
Main article: Candle snuffer
Candle snuffers are instruments used to extinguish burning candles by smothering the flame with a small metal cup that is suspended from a long handle, and thus depriving it of oxygen. An older meaning refers to a scissor-like tool used to trim the wick of a candle. With skill, this could be done without extinguishing the flame. The instrument now known as a candle snuffer was formerly called an "extinguisher" or "douter".
See also
Candle-making
Candle warmer
Candelabra
Julleuchter
Outdoor candle
Rushlight
Singing candle
Tealight
Trick candles
Trudon
Unity candle
Soap is a salt of a fatty acid[1] used in a variety of cleansing and lubricating products. Household uses for soaps include washing, bathing, and other types of housekeeping, where soaps act as surfactants, emulsifying[2] oils to enable them to be carried away by water. In industry, they are used as thickeners, components of some lubricants, and precursors to catalysts.
Types of soaps
Since they are salts of fatty acids, soaps have the general formula (RCO2−)nMn+ (Where R is an alkyl, M is a metal and n is the charge of the cation). The major classification of soaps is determined by the identity of Mn+. When M is Na or K, the soaps are called toilet soaps, used for handwashing. Many metal dications (Mg2+, Ca2+, and others) give metallic soap. When M is Li, the result is lithium soap (e.g., lithium stearate), which is used in high-performance greases.[3]
Non-toilet soaps
Soaps are key components of most lubricating greases and thickeners. Greases are usually emulsions of calcium soap or lithium soap and mineral oil.[4] Many other metallic soaps are also useful, including those of aluminium, sodium, and mixtures thereof. Such soaps are also used as thickeners to increase the viscosity of oils. In ancient times, lubricating greases were made by the addition of lime to olive oil.[5]
Metal soaps are also included in modern artists' oil paints formulations as a rheology modifier.[6]
Production of metallic soaps
Most metal soaps are prepared by neutralization of purified fatty acids:
2 RCO2H + CaO → (RCO2)2Ca + H2O
Toilet soaps
In a domestic setting, "soap" usually refers to what is technically called a toilet soap, used for household and personal cleaning. When used for cleaning, soap solubilizes particles and grime, which can then be separated from the article being cleaned. The insoluble oil/fat molecules become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water making it soluble. Anything that is soluble will be washed away with the water.
Structure of a micelle, a cell-like structure formed by the aggregation of soap subunits (such as sodium stearate): The exterior of the micelle is hydrophilic (attracted to water) and the interior is lipophilic (attracted to oils).
Production of toilet soaps
The production of toilet soaps usually entails saponification of fats (triglycerides). Triglycerides are vegetable or animal oils and fats. An alkaline solution (often lye or sodium hydroxide) induces saponification whereby the triglyceride fats first hydrolyze into salts of fatty acids. Glycerol (glycerin) is liberated. The glycerin can remain in the soap product as a softening agent, although it is sometimes separated.[7]
The type of alkali metal used determines the kind of soap product. Sodium soaps, prepared from sodium hydroxide, are firm, whereas potassium soaps, derived from potassium hydroxide, are softer or often liquid. Historically, potassium hydroxide was extracted from the ashes of bracken or other plants. Lithium soaps also tend to be hard. These are used exclusively in greases.
For making toilet soaps, triglycerides (oils and fats) are derived from coconut, olive, or palm oils, as well as tallow.[8] Triglyceride is the chemical name for the triesters of fatty acids and glycerin. Tallow, i.e., rendered beef fat, is the most available triglyceride from animals. Each species offers quite different fatty acid content, resulting in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil, sometimes called Castile soap or Marseille soap, is reputed for its particular mildness. The term "Castile" is also sometimes applied to soaps from a mixture of oils, but a high percentage of olive oil.
Fatty acid content of various fats used for soapmaking
Lauric acid Myristic acid Palmitic acid Stearic acid Oleic acid Linoleic acid Linolenic acid
fats C12 saturated C14 saturated C16 saturated C18 saturated C18 monounsaturated C18 diunsaturated C18 triunsaturated
Tallow 0 4 28 23 35 2 1
Coconut oil 48 18 9 3 7 2 0
Palm kernel oil 46 16 8 3 12 2 0
Laurel oil 54 0 0 0 15 17 0
Olive oil 0 0 11 2 78 10 0
Canola oil 0 1 3 2 58 9 23
History
Ancient Middle East
Box for Amigo del Obrero (Worker's Friend) soap from the 20th century, part of the Museo del Objeto del Objeto collection
The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BC in ancient Babylon.[9] A formula for soap consisting of water, alkali, and cassia oil was written on a Babylonian clay tablet around 2200 BC.
The Ebers papyrus (Egypt, 1550 BC) indicates the ancient Egyptians bathed regularly and combined animal and vegetable oils with alkaline salts to create a soap-like substance. Egyptian documents mention a similar substance was used in the preparation of wool for weaving.[citation needed]
In the reign of Nabonidus (556–539 BC), a recipe for soap consisted of uhulu [ashes], cypress [oil] and sesame [seed oil] "for washing the stones for the servant girls".[10]
In ancient Israel, the ashes from barilla plants, such as species of Salsola, saltwort (Seidlitzia rosmarinus) and Anabasis, were used in soap production, known as potash.[11][12] Soap made from potash (a concentrate of burnt wood or vegetable ashes mixed with lard or olive oil) is alkaline. If animal lard were used, it was heated and kept lukewarm (not boiling hot; neither cold). Lard, collected from suet, needed to be rendered and strained before being used with ashes (with the recommended consistency of 1 cup of lard to 3/8 cup of concentrated ash water). Traditionally, olive oil was used instead of animal lard throughout the Levant, which was boiled in a copper cauldron for several days.[13] As the boiling progresses, alkali ashes and smaller quantities of quicklime were added, and constantly stirred.[13] In the case of lard, it required constant stirring while kept lukewarm until it began to trace. Once it began to thicken, the brew was poured into a mold and left to cool and harden for 2 weeks. After hardening, it was cut into smaller cakes. Aromatic herbs were often added to the rendered soap to impart their fragrance, such as yarrow leaves, lavender, germander, etc. The ancient method here described is still in use in the production of Nabulsi soap.
Roman Empire
The word sapo, Latin for soap, likely was borrowed from an early Germanic language and is cognate with Latin sebum, "tallow". It first appears in Pliny the Elder's account,[14] 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 the men of the Gauls and Germans were more likely to use it than their female counterparts.[15] The Romans avoided washing with harsh soaps before encountering the milder soaps used by the Gauls around 58 BC.[16] Aretaeus of Cappadocia, writing in the 1st century AD, observes among "Celts, which are men called Gauls, those alkaline substances that are made into balls [...] called soap".[17] The Romans' preferred method of cleaning the body was to massage oil into the skin and then scrape away both the oil and any dirt with a strigil. The Gauls used soap made from animal fat.
Zosimos of Panopolis, circa 300 AD, describes soap and soapmaking.[18] Galen describes soap-making using lye and prescribes washing to carry away impurities from the body and clothes. The use of soap for personal cleanliness became increasingly common in the 2nd century AD. According to Galen, the best soaps were Germanic, and soaps from Gaul were second best.[18]
Ancient China
A detergent similar to soap was manufactured in ancient China from the seeds of Gleditsia sinensis.[19] Another traditional detergent is a mixture of pig pancreas and plant ash called "Zhu yi zi". True soap, made of animal fat, did not appear in China until the modern era.[20] Soap-like detergents were not as popular as ointments and creams.[19]
Islamic Middle East
Hard toilet soap with a pleasant smell was produced in the Middle East during the Islamic Golden Age, when soap-making became an established industry. Recipes for soap-making are described by Muhammad ibn Zakariya al-Razi (854–925), who also gave a recipe for producing glycerine from olive oil. In the Middle East, soap was produced from the interaction of fatty oils and fats with alkali. In Syria, soap was produced using olive oil together with alkali and lime. Soap was exported from Syria to other parts of the Muslim world and to Europe.[21]
A 12th-century Islamic document describes the process of soap production.[22] It mentions the key ingredient, alkali, which later becomes crucial to modern chemistry, derived from al-qaly or "ashes".
By the 13th century, the manufacture of soap in the Islamic world had become virtually industrialized, with sources in Nablus, Fes, Damascus, and Aleppo.[23][24]
Medieval Europe
Soapmakers in Naples were members of a guild in the late sixth century (then under the control of the Eastern Roman Empire),[25] and in the eighth century, soap-making was well known in Italy and Spain.[26] The Carolingian capitulary De Villis, dating to around 800, representing the royal will of Charlemagne, mentions soap as being one of the products the stewards of royal estates are to tally. The lands of Medieval Spain were a leading soapmaker by 800, and soapmaking began in the Kingdom of England about 1200.[27] Soapmaking is mentioned both as "women's work" and as the produce of "good workmen" alongside other necessities, such as the produce of carpenters, blacksmiths, and bakers.[28]
In Europe, soap in the 9th century was produced from animal fats and had an unpleasant smell. Hard toilet soap with a pleasant smell was later imported from the Middle East.[21]
15th–18th centuries
Advertising at Dobbins' medicated toilet soap
A 1922 magazine advertisement for Palmolive Soap
Liquid soap
Manufacturing process of soaps/detergents
In France, by the second half of the 15th century, the semi-industrialized professional manufacture of soap was concentrated in a few centers of Provence—Toulon, Hyères, and Marseille—which supplied the rest of France.[29] In Marseilles, by 1525, production was concentrated in at least two factories, and soap production at Marseille tended to eclipse the other Provençal centers.[30] English manufacture tended to concentrate in London.[31]
Finer soaps were later produced in Europe from the 16th century, using vegetable oils (such as olive oil) as opposed to animal fats. Many of these soaps are still produced, both industrially and by small-scale artisans. Castile soap is a popular example of the vegetable-only soaps derived from the oldest "white soap" of Italy.
Industrially manufactured bar soaps became available in the late 18th century, as advertising campaigns in Europe and America promoted popular awareness of the relationship between cleanliness and health.[32] In modern times, the use of soap has become commonplace in industrialized nations due to a better understanding of the role of hygiene in reducing the population size of pathogenic microorganisms.
19th century
Ad for Soapine, circa 1900, indicating that it is made of whale oil
Until the Industrial Revolution, soapmaking was conducted on a small scale and the product was rough. In 1780, James Keir established a chemical works at Tipton, for the manufacture of alkali from the sulfates of potash and soda, to which he afterwards added a soap manufactory. The method of extraction proceeded on a discovery of Keir's. In 1790, Nicolas Leblanc discovered how to make alkali from common salt.[16] Andrew Pears started making a high-quality, transparent soap in 1807[33] in London. His son-in-law, Thomas J. Barratt, opened a factory in Isleworth in 1862.
During the Restoration era (February 1665 – August 1714) a soap tax was introduced in England, which meant that until the mid-1800s, soap was a luxury, used regularly only by the well-to-do. The soap manufacturing process was closely supervised by revenue officials who made sure that soapmakers' equipment was kept under lock and key when not being supervised. Moreover, soap could not be produced by small makers because of a law which stipulated that soap boilers must manufacture a minimum quantity of one imperial ton at each boiling, which placed the process beyond reach of the average person. The soap trade was boosted and deregulated when the tax was repealed in 1853.[34][35][36]
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. American manufacturer Benjamin T. Babbitt introduced marketing innovations that included sale of bar soap and distribution of product samples. William Hesketh Lever and his brother, James, bought a small soap works in Warrington in 1886 and founded what is still one of the largest soap businesses, formerly called Lever Brothers and now called Unilever. These soap businesses were among the first to employ large-scale advertising campaigns.
Liquid soap
See also: Detergent
Liquid soap was not invented until the nineteenth century; in 1865, William Shepphard patented a liquid version of soap.[37] In 1898, B.J. Johnson developed a soap derived from palm and olive oils; his company, the B.J. Johnson Soap Company, introduced "Palmolive" brand soap that same year.[38] This new brand of soap became popular rapidly, and to such a degree that B.J. Johnson Soap Company changed its name to Palmolive.[39]
In the early 1900s, other companies began to develop their own liquid soaps. Such products as Pine-Sol and Tide appeared on the market, making the process of cleaning things other than skin, such as clothing, floors, and bathrooms, much easier.
Liquid soap also works better for more traditional or non-machine washing methods, such as using a washboard.[40]
Soap-making for hobbyists
A variety of methods are available for hobbyists to make soap.[41] Most soapmakers use processes where the glycerol remains in the product, and the saponification continues for many days after the soap is poured into molds. The glycerol is left during the hot-process method, but at the high temperature employed, the reaction is practically completed in the kettle, before the soap is poured into molds. This simple and quick process is employed in small factories all over the world.
Handmade soap from the cold process also differs from industrially made soap in that an excess of fat is used, beyond that needed to consume the alkali (in a cold-pour process, this excess fat is called "superfatting"), and the glycerol left in acts as a moisturizing agent. However, the glycerine also makes the soap softer. Addition of glycerol and processing of this soap produces glycerin soap. Superfatted soap is more skin-friendly than one without extra fat, although it can leave a "greasy" feel. Sometimes, an emollient is added, such as jojoba oil or shea butter.[citation needed] Sand or pumice may be added to produce a scouring soap. The scouring agents serve to remove dead cells from the skin surface being cleaned. This process is called exfoliation.
The lye is dissolved in water.
To make antibacterial soap, compounds such as triclosan or triclocarban can be added. There is some concern that use of antibacterial soaps and other products might encourage antibiotic resistance in microorganisms.[42]