Charcoal



Charcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by heating wood, sugar, bone char, or others substances in the absence of oxygen (see Charring). The soft, brittle, lightweight, black, porous material resembles coal and is 85% to 98% carbon with the remainder consisting of volatile chemicals and ash.

The first part of the word is of obscure origin, but the first use of the term "coal" in English language was as a reference to charcoal. In this compound term, the prefix "chare-" meant "turn," with the literal meaning being "to turn to coal." The independent use of "char," meaning to scorch, to reduce to carbon, is comparatively recent and must be a back-formation from the earlier charcoal. It may be a use of the word charren or churn, meaning to turn, i.e. wood changed or turned to coal, or it may be from the French (language) charbon. A person who manufactured charcoal was formerly known as a wiktionary:collier, though the term was used later for those who dealt in coal, and the ships that transported it.

Production )Production of wood charcoal in districts where there is an abundance of wood dates back to a very remote period, and generally consists of piling billets of wood on their ends so as to form a conical pile, openings being left at the bottom to admit air, with a central shaft to serve as a flue. The whole pile is covered with turf or moistened clay. The firing is begun at the bottom of the flue, and gradually spreads outwards and upwards. The success of the operation depends upon the rate of the combustion. Under average conditions, 100 parts of wood yield about 60 parts by volume, or 25 parts by weight, of charcoal; small scale production on the spot often yields only about 50%, large scale was efficient to about 90% even by the 17th century. The operation is so delicate that it was generally left to professional charcoal burners. These often worked in solitary groups in the woods and had a rather bad social reputation, especially traveling ones who often sold a sack (priced at about a day's wage) with lots of rubbish mixed in to farmers and townsfolk.

Historically the massive production of charcoal (at its height employment hundreds of thousands, mainly in Alpine and neighbouring forests) has been a major cause of deforestation, especially in Central Europe. In England, many woods were managed as coppices, which were cut and regrew cyclically, so that a steady supply of charcoal would be available (in principle) forever; complaints (as early as in Stuart England) about shortages may relate to the results of temporary over-exploitation or the impossibility of increasing production. The increasing scarcity of easily harvested wood was a major factor for the switch to the fossil fuel equivalents, mainly coal and brown coal for industrial use.

The modern process of carbonizing wood, either in small pieces or as sawdust in cast iron retorts, is extensively practiced where wood is scarce, and also by reason of the recovery of valuable byproducts (wood spirit, pyroligneous acid, tar), which the process permits. The question of the temperature of the carbonization is important; according to J. Percy, wood becomes brown at 220°C, a deep brown-black after some time at 280°, and an easily powdered mass at 310°. Charcoal made at 300° is brown, soft and friable, and readily inflames at 380°; made at higher temperatures it is hard and brittle, and does not fire until heated to about 700°.

In Finland and Scandinavia, the charcoal was considered the by-product of tar production. The best tar came from pine, thus pinewoods were cut down for tar pyrolysis. The residual charcoal was widely used as substitute for metallurgy coke (fuel) on blast furnaces for smelting. Tar production led to rapid deforestation: it has been estimated all Finnish forests are younger than 300 years by their age. The end of tar production in the end of the 19th century meant also rapid re-forestation.

Uses One of the most important historical applications of wood charcoal was as a constituent of gunpowder. It was also used in metallurgy operations as a reducing agent, but its application has been diminished by the introduction of coke (fuel), anthracite smalls, etc. A limited quantity is made up into the form of drawing crayons; but the greatest amount is used as a fuel, which burns hotter and cleaner than wood. Charcoal is often used by blacksmiths, for cooking, and for other industrial applications.

Industrial Fuel Historically, charcoal was used in great quantities for smelting iron in bloomery and later blast furnaces and finery forges. This was replaced for this by coke (fuel) during the Industrial Revolution. For this purpose, charcoal in England was measured in dozens (or loads) consisting of 12 sacks or shems or seams, each of 8 bushels.

Commercially, charcoal is often found in either lump, briquette or extruded forms:

The characteristics of charcoal products (lump, briquette or extruded forms) vary widely from product to product. Thus it is a common misconception to stereotype any kind of charcoal, saying which burns hotter, etc.

Charcoal is sometimes used to power commercial road vehicles, usually buses - in countries where oil is scarce or completely unavailable. In the years immediately after the World War II, charcoal buses were in regular use in Japan and are still used today in North Korea. Tokyo views of the city; essay contains a small section on Charcoal buses in post-war Japan

Purification/Filtration The porosity of Activated carbon accounts for its ability to readily Adsorbtion gases and liquids; charcoal is often used to filter water or adsorb odors. Its pharmacological action depends on the same property; it adsorbs the gases of the stomach and intestines, and also liquids and solids (hence its use in the treatment of certain toxin). Charcoal filters are used in some types of gas mask to remove poisonous gases from inhaled air. Wood charcoal also to some extent removes coloring material from solutions, but animal charcoal is generally more effective.

Animal charcoal or bone black is the carbonaceous residue obtained by the dry distillation of bones; it contains only about 10% carbon, the remainder being calcium and magnesium phosphates (80%) and other inorganic material originally present in the bones. It is generally manufactured from the residues obtained in the Animal glue and gelatin industries. Its decolorizing power was applied in 1812 by Derosne to the clarification of the syrups obtained in sugar refining; but its use in this direction has now greatly diminished, owing to the introduction of more active and easily managed reagents. It is still used to some extent in laboratory practice. The decolorizing power is not permanent, becoming lost after using for some time; it may be revived, however, by washing and reheating.

Art

Charcoal is used in art for drawing, making rough sketches in painting, and is one of the possible media for making a Surrealist techniques#Parsemage. It must usually be preserved by the application of a fixative. Artists generally utilize charcoal in three forms:





Horticulture One additional use of charcoal rediscovered recently is in horticulture. Although United States gardeners have been using charcoal for a short while, research on Terra preta soils in the Amazon has found the widespread use of biochar by Pre-Columbian Era natives to turn otherwise unproductive soil into very rich soil. The technique may find modern application, both to improve soils and as a means of carbon sequestration.

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