A candle is a source of light, and sometimes a source of heat, consisting of a solid block of fuel (commonly wax) and an embedded wick.
Today, most candles are made from paraffin. Candles can also be made from beeswax, soy and other plant waxes, and tallow (a by-product of beef-fat rendering). Gel candles are made from a mixture of paraffin and plastic.
A candle manufacturer is traditionally known as a chandler. Various devices have been invented to hold candles, from simple tabletop candle holders, to elaborate chandeliers.
The heat of the match used to light the candle melts and vaporizes a small amount of fuel. Once vaporized, the fuel combines with oxygen in the atmosphere to form a 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, and the liquefied fuel is then vaporized to burn within the candle's flame.
The burning of the fuel takes place in several distinct regions (as evidenced by the various colors that can be seen within the candle's flame). Within the bluer regions, hydrogen is being separated from the fuel and burned to form water vapor. The brighter, yellower part of the flame is the remaining carbon being oxidized to form carbon dioxide.
As the mass of solid fuel is melted and consumed, the candle grows shorter. Portions of the wick that are not evaporating the liquid fuel are consumed in the flame. The incineration of the wick limits the exposed length 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 (~.7 cm), to promote slower, steady burning, and also to prevent smoking.
Fuel and candle holders
The candle can be made of paraffin (a byproduct of petroleum refining), stearin (now produced almost exclusively from palm waxes), beeswax (a byproduct of honey collection), gel (a mixture of resin and mineral oil), some plant waxes (generally palm, carnauba, bayberry, or soy), or tallow (rarely used since the introduction of affordable and cheap wax alternatives). The candle is produced in various colors, shapes, sizes and scents. The size of the flame and corresponding rate of burning is controlled largely by the candle wick.
The most basic production method generally entails the liquification of the solid fuel by the controlled application of heat. This liquid is then poured into a mold to produce a pillar type candle, a fireproof jar to produce a candle container, or a wick is repeatedly immersed in the liquid to create a dipped taper. Often, fragrance oils are added to the liquid wax prior to pouring. Natural scents, in the form of essential oils, can also be used. The candle may also be colored by the addition of some sort of coloring agent. This is almost always an aniline-based dye, although pigments can be used in some circumstances.
A candle typically produces about 13 lumens of visible light and 40 watts of heat, although this can vary depending primarily on the characteristics of the candle wick. For comparison, note that a 40 watt incandescent light bulb produces approximately 500 lumens for the same amount of power. The modern SI unit of luminous intensity, the candela, was 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.
It is commonly believed that candles made of beeswax burn more cleanly than petroleum-based paraffin waxes. Highly refined paraffin wax, however, can burn as or more cleanly than natural waxes, creating less particulates during combustion. The type of wick and inclusion of any scents and/or dyes have a much greater impact on the release of compounds, particulates, and smoke, regardless of the base material. The cleanest burning candle will be well-constructed, unscented, undyed, and burn in a draft-free area. A candle will burn well when formulated waxes are blended together (soy, paraffin and other waxes), and fragrance oils and wick selections are balanced properly.
A smoke film can be a concern to those who frequently burn a candle indoors and is also referred to as ghosting, carbon tracking, or carbon tracing. Smoke can be produced when a candle does not burn the wax fuel completely. A scented candle can be a source of candle smoke deposits. Trimming candle wicks to about 6 millimeters (¼ in) or shorter will keep smoking to a minimum. A flickering flame will produce more smoke, therefore a candle should be burned in an area free from drafts.
Differing opinions about which kind of wax in a candle is "natural." Proponents of the soy wax candle will note the material is biodegradable and "all natural." However, most soy beans used in the manufacture of soy wax are genetically modified. Paraffin wax, as used in candle making, is also biodegradable. It also often meets the United States Food and Drug Administration criteria for use in foods and food contact. It has also been claimed that natural waxes have a neutral carbon footprint as carbon dioxide was recently taken from the air to produce the natural wax, which upon burning would not result in a net increase in carbon dioxide.
A modern candle typically burns at a rate of about 0.105 g/min, releasing heat of about 77 W, plus or minus about 9 W. The light produced is about 13 lumens. The luminous efficacy is about 0.17 lumens per watt (luminous efficacy of a source), a hundred times lower than an incandescent light bulb. The color temperature is approximately 1,000K.
The hottest part of the 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. However note that that 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 .
The flicker frequency of a flame is proportional to the square root of the ratio of the acceleration due to gravity to the diameter of the candle. A candle on the moon would flicker at a different frequency than on Earth and wouldn't flicker at all in the absence of a gravitational force (like on a space platform).
According to the National Fire Protection Association, candles are one of the leading sources of residential fires with almost 10% of civilian injuries and 6% of civilian fatalities attributed to candles.
A candle flame that is longer than its laminar smoke point  will emit soot. Soot inhalation has known health hazards. Proper wick trimming will prevent 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. When placed over the flame the oxygen supply is cut off. They were used daily when the candle was the main source of lighting a home, before electric lights were available.
Glass candle holders are sometimes cracked by thermal shock from the candle flame, particularly when the candle burns down to the end.
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. Imported candles may still be found to have some lead core wicks. 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.
Decorative candle holders, 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. Any candle that is too large can be trimmed to fit with a knife; a candle that is too small can be fitted with aluminum 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 fire proof 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.
In Rome, around the first century, candles were made out of tallow and the pith of rushes. The Latin word candere means to flicker. The Egyptians and Cretans made the candle from beeswax, as early as 3000 BC. The early candle was made from various forms of natural fat, tallow, and wax. In the 18th century, spermaceti, oil produced by the sperm whale, was used to produce a superior candle. Late in the 18th century, colza oil and rapeseed oil came into use as much cheaper substitutes. Paraffin was first distilled in 1830, and revolutionized candle-making, as it was an inexpensive material which produced a high-quality, odorless candle that burned reasonably cleanly. The industry was devastated soon after, however, by the distillation of kerosene (confusingly also called paraffin oil or just paraffin). Recently resin based candles that are freestanding and transparent have been developed, with the claim that they burn longer than traditional paraffin candles. They are usually scented and oil based.
With the fairly consistent and measurable burning of a candle, a common use 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. 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. A form of candle-clock was used in coal-mining until the 20th century.
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", although this term is also used to refer to a candle that decorates an Advent wreath.
Candles and religion
Candles are a traditional part of Buddhist ritual observances. Along with incense and flowers, candles (or some other type of light source, such as butter lamps) are placed before Buddhist shrines or images of the Buddha as a show of respect. They may also be accompanied by offerings of food and drink. The light of the candles is described as representing the light of the Buddha's teachings, echoing the metaphor of light used in various Buddhist scriptures. See Ubon Ratchathani Candle Festival for an example of a Buddhist festival that makes extensive use of candles.
In almost all Hindu homes, lamps are lit daily and sometimes every day before an altar. In some houses, the lamps, or candles, at dawn, and in some, twice a day - at dawn and dusk - and in a few, it is maintained continuously.
A diya, or clay lamp, is frequently used in Hindu celebrations and forms an integral part in many social rites. It is a strong symbol of enlightenment and prosperity.
In its traditional and simplest form, the diya is made from baked clay or terracotta and holds oil or ghee that is lit via a cotton wick.
Traditional diyas have now evolved into a form wherein waxes are being used as replacements for oils.
In Christianity the candle is commonly used in worship both for decoration and ambiance, and as a symbol that represent the light of God or, specifically, the light of Christ. The altar candle is often placed on the altar, usually in pairs. Candles are also carried in processions, especially to either side of the processional cross. A votive candle or taper may be lit as an accompaniment to prayer.
Candles are lit by worshippers in front of icons in Eastern Orthodox, Oriental Orthodox, Eastern Catholic and other churches. This is referred to as "offering a candle", because the candle is a symbol of the worshiper offering himself or herself to God (and proceeds from the sale of the candle are offerings by the faithful which go to help the church). Among the Eastern Orthodox, there are times when the entire congregation stands holding lit tapers, such as during the reading of the Matins Gospels on Good Friday, the Lamentations on Holy Saturday, funerals, Memorial services, etc. There are also special candles that are used by Orthodox clergy. A bishop will bless using dikirion and trikirion (candlesticks holding two and three candles, respectively). At Pascha (Easter) the priest holds a special Paschal trikirion, and the deacon holds a Paschal candle. The priest will also bless the faithful with a single candle during the Liturgy of the Presanctified Gifts (celebrated only during Great Lent).
In the Roman Catholic Church a liturgical candle must be made of at least 51% beeswax, the remainder may be paraffin or some other substance. In the Orthodox Church, the tapers offered should be 100% beeswax, unless poverty makes this impossible. The stumps from burned candles can be saved and melted down to make new candles.
In some Western churches, a special candle known as the Paschal candle, specifically represents the Resurrected Christ and is lit only at Easter, funerals, and baptisms. In the Eastern Orthodox Church, during Bright Week (Easter Week) the priest holds a special Paschal trikirion (triple candlestick) and the deacon holds a large candle during all of the services at which they serve.
In many Western churches, a group of candles arranged in a ring, known as an Advent wreath, are used in church services in the Sundays leading up to Christmas. In households in some Western European countries, a single candle marked with the days of December is gradually burned down, day by day, to mark the passing of the days of Advent; this is called an Advent candle.
In Judaism, a pair of candles are lit on Friday evening prior to the start of the weekly Sabbath celebration. On Saturday night, a special candle with several wicks is lit for the Havdalah ritual marking the end of the Sabbath and the beginning of the new week.
A memorial candle is lit on the Yahrtzeit, or anniversary of the death of a loved one according to the Hebrew calendar. The candle burns for twenty-four hours. A memorial candle is also lit on Yom HaShoah, a day of remembrance for all those who perished in the Holocaust.
The candle is also used in celebrations of Kwanzaa, which is an African American holiday which runs from December 26 to January 1. A Kinara is used to hold candles in these celebrations. It holds seven candles; three red candles to represent African American struggles, one black candle to represent the African American people and three green candles to represent African American hopes.
A common element of worship in many Unitarian Universalism churches and fellowships is the lighting of candles of joy and concern. Here members of the congregation may come up to the altar or chancel, light a votive or other candle, and share a personal concern or joy with the community. Unitarian Universalism also incorporates candle-lighting ceremonies from other spiritual traditions, from which they draw inspiration.
In Wicca and related forms of Paganism, the candle is frequently used on the altar to represent the presence of the God and Goddess, and in the four corners of a ritual circle to represent the presence of the four classical elements: Fire, Earth, Air, and Water. When used in this manner, lighting and extinguishing the candle marks the opening and closing of the ritual. The candle is also frequently used for magical meditative purposes. Altar candles are traditionally thick tall candles or long tapers which are available in many colors. In Wicca, the candles that are used come in a variety of colors, depending on the nature of the ritual or custom at hand. Some Wiccans may use red, green, blue, yellow and white or purple candles to represent the elements.
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- A Candle Eastern Orthodox usage
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