Charcoal production

Background

Although charcoal was used in a variety of metallurgical industries, in nineteenth century Pennsylvania, charcoal was produced primarily to fuel iron production. Charcoal is the result of the destructive distillation of wood to yield a fuel that is primarily carbon. Charcoal was produced by colliers. Charcoal retains the texture of wood, is black in color, and is fragile under pressure. Charcoal was used in iron production rather than pure wood because charcoal burns much hotter and more consistently. In the nineteenth century, when iron production was at its peak, the demand for charcoal as fuel for furnaces directly impacted forests. As a result, the charcoal industry was one of the first to think about sustainability and forestry. Unlike wood, charcoal was not attacked by insects or fungi, and could be stored indefinitely, and was a more concentrated heat source (producing about one and a half times more heat than an equivalent weight of dry wood. (pg. 59, History on the Road, Thomas Stratka and Wayne Ramer)

Types of Wood

While most types of wood can become charcoal, hard woods generally produced the best quality charcoal. Trees like oak, hickory, chestnut, and elm were greatly preferred to softer woods, such as gum and poplar. Additionally, although resin rich wood, such as pine, are generally less desirable, they may be extensively used when it is widely available . However, heavier hardwood required a longer burning period, so sometimes a mixture of hardwood and softwood proved to be a combination that yielded the greatest quantity of charcoal without compromising the integrity of the material. The condition of wood was also important to the quality of the charcoal output, as knots in the wood, decay, and moisture all negatively impacted carbonization. The charcoal produced was not proportional to the original amount of wood. The burning process reduced the weight of the wood by roughly a quarter and the volume of the wood by half.

The wood was cut by woodcutters primarily during the winter months, as the trees would have less moisture inside. Two types of wood were cut: lap-wood and billets. Both were cut in a particular fashion that allowed them to slant inward when piled together. See Harvesting Wood.

Charcoal Production Process

Making the Hearth

Charcoal hearths required a large, flat, solid, and dry area that was typically thirty to forty feet in diameter. The ground would be tilled to remove any rocks or organic material from the area. The hearths were often constructed on hillsides to facilitate dirt movement and were usually round. When identifying the remains of charcoal hearths, the aforementioned information can be utilized. The soil at hearth site remains will typically also be darker in color and flecked with charcoal remains. Low places were avoided as they were typically prone to retaining water in the soil, which would have been detrimental to the charcoal production process. It was also important that the hearth area was accessible to wagons, so that the charcoal could be carted away. A triangular chimney was constructed from stacked wood in the center of the hearth. In the chimney, a large stick called the Fagan pole was inserted. The Fagan pole was used to mark the center of the pit (the term "pit" is not an accurate descriptor of the appearance of the hearth, as the structure was entirely above ground) and would be also be removed to provide draught just prior to the process of burning the wood. It was important that the hearth were not dug into the ground; rather, they were to sit slightly higher than the surface, as to allow water to drain away.

Piling the Wood

After the chimney and the pole were constructed, the collier leaned thick pieces of hardwood inward against the chimney and filled the gaps with lap-wood. It was important for the wood to be packed as closely together as possible to ensure uniform burning. After the first layer (the "foot") was created, the second layer (the "waist") was built up four feet in height. Then, a third layer (the "head") was added to the chimney, completing the structure. A pit may have held anywhere from twenty-five to fifty cords of wood at a time.

Covering the Wood

Piles were first covered with a layer of brushwood, leaves, or straw that is about an inch thick. Then, a layer of charcoal dust and dirt was added. The leaves acted as a barrier between the wood and the dirt, helping to ensure even charring of the wood by restricting air flow.

The Burning Process

Ignition likely occurred in the early morning, so that the colliers could attend to the hearth during the first crucial hours in daylight. Charcoal hearths were lit at the top and burned downwards. To ignite the wood, kindling was placed within the the chimney and the fagan pole was removed. Then, hot coals were dropped into the chimney and the opening was covered with a flat wood pieces called the "bridging." The bridging was then covered with leaves and straw before the burning began. Small holes or smoke-vents were created at the bottom of the pile to allow airflow for the draught and would be closely managed by the colliers.

The process typically took between ten to fourteen days; however, if conditions were unfavorable, the burning period could take three weeks. The type of wood, its quality, the way the wood was piled, and the number of cords also factored into the length of the burning process. The greater in size and dryness a billet was, the longer the coaling process would take. Throughout the process, the pit was carefully observed and diligently tended to by colliers to ensure that the wood was burning evenly, especially at the foot of the hearth. During the process the billets shrunk, and the collier needed to pack in more wood and dust to fill the gaps. At five hundred degrees Fahrenheit the wood began to break down; the maximum temperature reached during the process was about seven hundred fifty degrees Fahrenheit. Colliers needed to watch the color of the smoke and attend to the smoke-vents accordingly . White smoke was one of indicators of a proper burning, whereas brown tinted smoke, or "dangerous smoke," indicated that the smoke-vents had been created too far down in the pile and a fire broke out before the main burning reached the area, which resulted in a loss of charcoal. Throughout the burning process, the smoke would cycle through various colors and densities, which would indicate to the collier whether or not to adjust the smoke-vents at various times. At the beginning, the smoke would be thick and of a gray-white color and strong smell; but as the coaling process continued, the smoke would thin out and turn whiter in color, until the smoke became light blue, a signal that it was time to close the smoke-vets and open new ones farther down.

The process was ended before all the charcoal had finished burning because this helped colliers maximize production. Colliers would typically layer dust over the pile at the end of the burning process and pack it down tightly, leaving the charcoal to cool. In Sweden, the cooling process may sometimes have been aided by the use of water, where colliers would begin to water the air-tight mound after allowing it to remain undisturbed for twenty-four hours. Colliers would use flat, wooden scoops to toss water into the air so that it would fall onto the mound like rain, until the dust is no longer able to absorb the water. The colliers needed to remain vigilant and continue this process as the dust dried. The first few days of this process watering was required around two or three times a day; by the seventh day, watering was only necessary if the dust continued to dry.

Removing the Charcoal

To remove the finished charcoal, colliers cleared the area surrounding the hearth where the charcoal would be dragged on to and used a large rake with long tines to collect the charcoal. The tines ensured that the pieces of charcoal were dragged through the dirt on their way out of the hearth and that the charcoal would not be damaged, as it would have been if, for example, a shovel had been used for removal. This made sure that no fires would flare up and destroy the charcoal. It was helpful if colliers had a source of water nearby, as to extinguish any fires that threatened the consumption of the charcoal, but certainly not all charcoal production locations allowed for this. If the use of water became necessary and water was available, the collier needed to be careful to only use what was necessary to extinguish the fire, as to not sour the charcoal and lessen its value.

After the charcoal was removed, it was imperative that it be stored somewhere that it would not be affected by poor weather before being carted away. In some cases it was necessary that a charcoal shed be built to store the charcoal. The shed would be constructed from billets and situated on a dry area near the hearth.

Transporting Charcoal

Initially, most charcoal was moved from the hearths to local furnaces within about 2-5 miles by cart. As furnaces became larger in the late 1800s and early 1900s, charcoal was transported increasingly greater distances. This charcoal served the larger, more efficient furnaces, many of which were in the Midwest and South. In particular, the large furnaces of Michigan were highly dependent upon the movement of charcoal by train car.. Specialized charcoal cars were designed and widely used, especially in New England, New York, Pennsylvania, Michigan, Alabama and Tennessee. In 1882, Bernhard Fernow, the manager of the lands associated with the Lehigh Furnace, loaded 49 box cars with the charcoal of from "860 cords of chestnut, 25 years old, ... and 600 cords of black oak, 38 years old." The intended destination of this charcoal is unclear.

Sustainability

The need for charcoal in the iron industry created a significant demand for wood and a great deal of trees were chopped down for its production. The average output of furnaces between 1750 and 1800 was one hundred to four hundred tons of pig iron per year. This required two hundred to four hundred bushels of charcoal and fifty acres of trees to produce that amount. Even though the increased efficiency of furnaces decreased the necessary amount of charcoal, increased production required one hundred fifty acres of wood by 1850 and one thousand four hundred acres by 1900.

Since forests regenerated at different rates, this impacted sustainability. In the Western United States, woodlands took decades to regrow to maturity; so, forest sections usually were cut on a twenty-year cycle. Old-growth forests would typically have higher yields. Eastern furnaces were some of the first to manage forests to ensure a sustainable yield. Several early proponents of sustainable forestry were involved in the making of charcoal, like Bernhard E. Fernow, the manager of the Lehigh Furnace from 1879 to 1883. He advocated for coppicing of wood and protection from fire and cattle grazing to speed up regrowth of forest used for charcoal.

Charcoal versus Coal

The transition to coal as the primary fuel for furnaces began around 1840, but in 1859 around three-quarters of furnaces in America (particularly in Ohio, Pennsylvania, and New York) still primarily used charcoal. Charcoal remained a source of fuel in some places until 1945. Coal was chosen as a replacement for charcoal in part because it was less expensive to transport.

Charcoal, compared to coal, tended to produce a higher quality of iron with fewer impurities, partially because of its density. The use of charcoal also created less smoke using the production process. Iron made from charcoal had a "fine grain" and maintained a better cutting edge in comparison to coal. However, as coal became the primary source of fuel, production moved out of the forests and into cities, which allowed the forests to begin to recover from the impacts of charcoal production.

References

• Agriculture and Rural economy – Charcoal → . 2010. The Encyclopedia of Diderot & d'Alembert Collaborative Translation Project. Ann Arbor: Michigan Publishing, University of Michigan Library. [1] [2]. Originally published as "Agriculture et économie rustique – Charbon de bois," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, vol. 1 (plates) (Paris, 1762).

• Fernow, Bernhard E. 1882. The Yield of Wood and When to Cut It. Journal of the United States Association of Charcoal Iron Workers 3 (1): 19–26.

• Gemmell, Alfred. 1949. The Charcoal Iron Industry in the Perkiomen Valley. Norristown, PA.: Hartenstine Printing House.

• Jones, Claude A. 1976. Making Charcoal at Jacobsburg. In Slate Belt Bicentennial Heritage, edited by Marjorie May, Maryann Repsher, Robert R. Saltern, Gordon E. Wilson, and Albert M. Toth, 32–33. Heritage Committee of the Slate Belt Bicentennial Commission.

• Kemper, Jackson. 1941. American Charcoal Making in the Era of the Cold-Blast Furnace. History 14. Washington, D.C.: U.S. Department of the Interior; National Park Service.

• MeasuringWorth Foundation. 2020. Measuring Worth- Relative Worth Comparators and Data Sets. . Accessed April 24, 2020

• Overman, Frederick. 1854. The Manufacture of Iron, in all its Various Branches (3rd ed.). Philadelphia: Baird. [3]

• Straka, Thomas J., and Wayne C. Ramer. 2010. History on the Road: Hopewell Furnace National Historic Site. Forest History Today Spring/Fall: 58–62.[4]

• Straka, Thomas J. 2014. Historic Charcoal Production in the US and Forest Depletion: Development of Production Parameters. Advances in Historical Studies: 104-114.[5]

• Svedelius, G., Joseph Leonard W. Nicodemus, and Björn R. Anderson. 1875. Hand-book for Charcoal Burners. New York: Wiley. [6]

• Transportation of Charcoal. 1885. Journal of the United States Association of Charcoal Iron Workers 6 (2): 117–21.

• United States Census, 1860, database with images, FamilySearch [7] : 24 March 2017, Pennsylvania > Carbon > East Penn Township > image 2 of 22; from "1860 U.S. Federal Census - Population," database, Fold3.com (http://www.fold3.com : n.d.); citing NARA microfilm publication M653 (Washington, D.C.: National Archives and Records Administration, n.d.).

• Wagner, Van. 2008. Fire the Pit- Charcoal Production in Pennsylvania. 4 vols. [8]; [9]; [10]; [11]

• Walker, Joseph E. 1966. Hopewell Village; a Social and Economic History of an Iron-Making Community. Philadelphia,: Univ. of Pennsylvania Press.

• Williams, Michael. 1989. Americans and Their Forests : A Historical Geography. Cambridge [Cambridgeshire] ; Cambridge University Press.