Charcoal production

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Traditionally charcoal has been used in a variety of metallurgical industries[1], and in the case of nineteenth century Pennsylvania, charcoal was produced primarily as fuel for the region's iron production.The responsibility of charcoal production was predominately that of colliers. Charcoal is the result of the destructive distillation of wood which yields a fuel source that is mostly carbon[2][3]. The destructive distillation of wood is caused by partially burning (carbonizing) wood to remove water vapor and volatile gases, leaving behind a carbon residue known as charcoal.[4] When charcoal is produced the volume of the wood is reduced by roughly half of its initial volume and its weight is decreased by 25 percent, thus making charcoal an easily transported source of fuel[5]. Charcoal retains the texture of wood, is black in color, and is fragile under pressure[6]. Unlike wood, charcoal is not attacked by insects or fungi and could be stored indefinitely[7]. It was also easier to burn, produced less smoke, was a hotter more consistent source of heat, and could easily be moved[8]. It was these principal properties of charcoal that led iron producers to favor charcoal as a fuel source over unmodified wood as charcoal was ultimately a more profitable source of fuel[9]. 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[10].

Types of Wood

While most types of wood can become charcoal, hard woods generally produced the highest quality charcoal[11]. Trees such as oak, hickory, chestnut, and elm were often preferred to softer woods, such as gum and poplar[12]. Additionally, although resin rich woods, such as pine, are generally less desirable[13], they may be extensively used when it is widely available [14]. While hardwoods were typically favored, however they regularly required longer burning periods[15], therefore 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[16]. 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[17]. The wood for charcoal production was cut by woodcutters primarily during the winter months[18][19][20], as the trees would have less moisture inside[21]. Furnace operators preferred that woodcutters choose timber that was about 20 to 30 years old to harvest for charcoal production and most of the wood used was sourced from nearby forests[22]. Two types of wood were cut in this process: lap-wood and billets[23]. Most billets came from tree trunks and typically measured 4 to 7 inches in diameter, while most lap-wood came from branches and were about 1 and a half to 4 inches in diameter[24]. And while billets and lap-wood came from different parts of the tree, both were cut in a particular fashion that allowed them to slant inward when piled together[25]. See Harvesting Wood.

Charcoal Production Process

Making the Hearth

Because of high winter and spring winds and other unfavorable weather conditions, charcoal hearths were traditionally in operation only during the months from May until late October[26][27][28]. When choosing a location to construct a charcoal hearth colliers took a variety of factors into account such as dryness, accessibility and levelness[29]. Charcoal hearths required a large, flat, and dry area that typically measured between thirty and forty feet in diameter[30][31][32]. Once established, charcoal hearths were reused by colliers due to the fact they were rich with charcoal dust[33]. Ensuring the base of the hearth was strong and flat was important so as to afford good raking and shoveling of the coal[34]. It was paramount that the base of the charcoal pits stay dry as water and moisture were detrimental to the charcoal production process[35]. It was critical that the hearths were not dug into the ground; rather, they were to sit slightly higher than the surface, as to allow water to drain away from the base[36]. As a result of charcoal production’s relationship with water, low places were typically avoided as water naturally retains itself in these spaces[37]. Instead the hearths were often constructed on dry hillsides or mountain tops[38]. Colliers also made sure they built their hearths in place that were accessible to wagons so that the charcoal could be hauled off[39][40].. Before constructing the charcoal pit the colliers would till the ground in order to remove any rocks and organic material that may have been a disturbance to charcoal production[41]. Often time colliers managed up to eight or nine[42]charcoal hearths at a time and the hearths were normally situated about the distance of a city block from each other[43].

When identifying the remains of charcoal hearths, the aforementioned information can be utilized. The soil at hearth site remains will typically be darker in color than surrounding soil[44] and flecked with charcoal remains.

There were four different styles of hearths that were constructed and each design had a different capacity of wood. The first, and largest was a square or rectangular hearth which held about 60-100 cords of wood. The second was a round shape that held about 50 cords. The next, a conical hearth, held around 15-40 cords. And finally, a beehive shape held between 20-50 cords of woods[45]. The beehive kiln is very similar in appearance to the conical but there are still some differentiations such as the beehive not having a dome top.

Piling the Wood

Once the hearth was prepared the collier placed the fagan pole in the center of the pit and proceeded to construct the hearth's chimney around this pole with lap wood[46][47].The fagan pole was a green pole that measured at about 18 feet tall and three to four inches in diameter; the pole would be also be removed to provide draught just prior to the process of burning the wood[48][49]. Typically the chimneys took on a triangular form and had an opening of about 8 inches[50]. After the base of the chimney and pole were constructed, the collier began to construct the first layer (the "foot"), this was done by leaning thick pieces of hardwood (called billets) inward against the chimney and by filling the gaps with lap-wood[51][52]. The billets were placed in this protruding manner, so that when the ring of charcoal dust finally was reached there would be enough slope to the sides of the pit to enable the final covering of leaves and dust to rest securely without sliding off[53]. It was important that the wood was packed as closely together as possible to ensure uniform burning[54][55]. After the first layer was created, the second layer (the "waist") was built and this layer was also comprised of billets and lap wood[56][57]. This second layer measured about 4 feet in height [58][59]. Then, a third layer (the "head") of horizontally placed pieces of lap-wood was added to the chimney, completing the structure[60][61]. A pit may have held anywhere from twenty-five to fifty cords of wood at a time[62].

Covering the Wood

The last step in the process of constructing the wood pile is known as "Lapping-off"; this was when colliers covered their wood piles with a layer of leftover lap-wood with the intention of filling in any possible air spaces or cracks[63][64]. The lap-wood was then covered by leaves and straw, which were collected on site by the collier or their helpers. This layering of brush typically amounted to a covering of a few inches[65][66]. Then, a layer of charcoal dust and/or dirt was added[67][68]. This final covering acted as a barrier between the wood and the dirt, helping to ensure even charring of the wood by restricting air flow[69]. Throughout the entire operation great care was taken to set and fit the pieces substantially together to prevent the whole from reeling or twisting. A pit hastily slapped together was certain to reel[70].

The Burning Process

Ignition of the charcoal pits typically occurred in the later parts of the evening, this was done so that the colliers could sleep one more time before they had to constantly watch the pit. Normally the pit would not require the attention of the collier until the following afternoon[71]. However some historical records contradict the notion that charcoal pits were usually lit late in the evening, and sources such as Svedelius's 1875 Handbook for Charcoal Burners state that ignition likely occurred in the early morning, so that the colliers could attend to the hearth during the first crucial hours in daylight[72]. Charcoal hearths were lit at the top and burned downwards[73][74]. To ignite the wood, kindling was placed within the the chimney and the fagan pole was removed[75][76]. Then, hot coals were dropped into the chimney[77][78] and the opening was covered with a flat wood pieces called the "bridging"[79]. The bridging was then covered with leaves and straw[80] before the burning began. Small holes or smoke-vents were created at the bottom of the pile to allow airflow for the draught[81] 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[82][83]. 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[84]. The greater in size and dryness a billet was, the longer the coaling process would take[85]. Throughout the process, the pit was carefully observed and diligently tended to by colliers to ensure that the wood was burning evenly[86], especially at the foot of the hearth[87]. Colliers were trained to be a master in recognizing different surfaces based on their feel of the fagan.[88]. A master collier and one or two helpers “coaled” together, working as many as eight or nine pits at a time all of which required attentive handling as any burning flame could jeopardize the final product[89][90]. As the charring process continued, pockets developed in the pit as a result of the billets shrinking[91]; the collier walks the pile, called “jumping the pit” to locate them and any soft spots are filled in with more wood[92][93].From time to time the colliers would check the status of the charcoal by poking the fagan pole down the chimney in order to reason how far along they were in the burning process [94]. 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[95].

Colliers needed to watch the color of the smoke and attend to the smoke-vents accordingly [96]. Historical documents and modern scholarship have produced contradicting information regarding what different color smoke represented in the charcoal making process. Some experts such as Thomas Straka and Wayne Ramer claim white smoke was one of indicators of a proper burning[97]. This is in direct contradiction to Jackson Kemper and his charcoal production research, Kemper contends that white smoke was an indication of a poorly charring pit as result of rapid burning[98]. Kemper states that a well burning pit puffed blue smoke from its vents in lazy intervals, however others maintain that blue smoke was a signal to colliers to close up the smoke vents and open new ones further down[99][100]. Other accounts assert that brown tinted smoke was undesirable and indicative of poorly placed smoke-vents which had been constructed too far down in the pile[101]. This could cause a fire to break out before the main burning reached the area resulting in a loss of charcoal[102].

The process was ended before all the charcoal had finished burning because this helped colliers maximize production[103]. 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[104]. 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[105]. 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[106]. The colliers needed to remain vigilant and continue this process as the dust dried[107]. 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[108].

Removing the Charcoal

To remove the finished charcoal, colliers cleared the area surrounding the hearth where the charcoal would be dragged on to[109] and used a large rake with long tines to collect the charcoal[110][111]. 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[112], as it would have been if, for example, a shovel had been used for removal[113]. The rake has long spokes that are evenly spaced out to ensure that smaller and larger pieces of charcoal get picked up. Raking out the coal can take as many as two to three days. One man explains that they are “foxing the brands”[114] which means that any pieces of coal that are still charring need to be kept under the soil to properly char. This made sure that no fires would flare up and destroy the charcoal[115]. It was helpful if colliers had a source of water nearby, as to extinguish any fires that threatened the consumption of the charcoal[116], but certainly not all charcoal production locations allowed for this and dust was often used as a substitute for water[117]. 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[118].It is important to note that charcoal makers did not want small pieces but rather, favored larger chunks that had to be loaded by hand.

After the charcoal was removed, it was imperative that it be stored somewhere that it would not be affected by poor weather[119] before being carted away. In some cases it was necessary that a charcoal shed be built to store the charcoal[120]. The shed would be constructed from billets and situated on a dry area near the hearth[121]. Once the charcoal cooled down and the threat of reignition past, the charcoal was removed from the cooling shed and moved to the charcoal house[122].

Transporting Charcoal

Initially, most charcoal was moved by cart from the hearths to local furnaces within about 2-5 miles of the charcoal production site. 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.[123]. Specialized charcoal cars were designed and widely used, especially in New England, New York, Pennsylvania, Michigan, Alabama and Tennessee[124]. Historical records are important in helping us glean new information about chracoal transportation. Records show that 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." [125] And while the intended destination of this charcoal is unclear, we can approximate each rail car held roughly 30 cords of wood.


The need for charcoal in the iron industry created a significant demand for wood and a great deal timber was cut for charcoal production[126]. The average output of furnaces between 1750 and 1800 was one hundred to four hundred tons of pig iron per year. To fulfill these iron production levels two hundred to four hundred bushels of charcoal were required and in order to meet these requirements about 50 acres of timber was needed per furnace[127]. Even though the increased efficiency of furnaces decreased the requisite amount of charcoal, increased production required one hundred fifty acres of wood by 1850 and one thousand four hundred acres by 1900[128].

Iron production left a pronounced impact on our woodlands and since forests regenerated at different rates, this raised important questions about sustainability. In the Western United States, woodlands took decades to regrow to maturity; so, forest sections usually were cut on a twenty-year cycle[129]. Occasionally iron furnaces became unprofitable enterprises because they exhausted all the nearby wood supplies and would have to halt production only the second growth timber was ready[130]. Old-growth forests would typically have higher yields and this incentivized the charcoal industry to properly manage forests and allow wood to reach its full potential[131]. Iron furnaces in the eastern United States were some of the first to manage forests to ensure a sustainable yield[132]. 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[133]. The transition to coal from charcoal in the iron production industry and the subsequent changes in production sites allowed many forests to begin recovering from the charcoal production process. need a citation*

Charcoal versus Coal

The transition to coal as the primary fuel for furnaces began around 1840, however this transition did not occur overnight and in 1859 around three-quarters of furnaces in America (particularly in Ohio, Pennsylvania, and New York) were still using charcoal as their primary fuel source.[134]. Charcoal remained a source of fuel in some places until 1945[135]. Coal was chosen as a replacement for charcoal in part because it was less expensive to transport[136]. Coal being less expensive to transport in comparison to charcoal was largely due to the fact that coal was less bulky and was sourced from established mines unlike charcoal which was produced from scattered timber sources in less accessible locations[137]. And while coal succeeded charcoal as the primary fuel source for iron production, charcoal tended to produce a higher quality of iron with fewer impurities[138]. The use of charcoal also created less smoke using the production process and iron made from charcoal had a "fine grain" and maintained a better cutting edge[139].


  1. Whitney 1994, 218
  2. Straka 2014, 106
  3. Walker 1966, 242
  4. Straka and Ramer 2010, 59
  5. Straka and Ramer 2010, 59
  6. Svedelius 1875, 20
  7. Straka and Ramer 2010, 59
  8. Straka 2014, 106; Whitney 1994, 218
  9. Straka and Ramer 2010, 59
  10. Straka and Ramer 2010, 58
  11. Kemper 1941, 18
  12. Straka and Ramer 2010, 59
  13. Overman 1854, 81
  14. see Svedelius
  15. Straka and Ramer 2010, 59
  16. Straka 2014, 106
  17. Straka 2014, 106
  18. Straka and Ramer 2010, 59
  19. Kemper 1941, 12
  20. Walker 1966, 230
  21. Svedelius 1875, 6; Overman 1854, 80
  22. Straka and Ramer 2010, 60-61
  23. Straka and Ramer 2010, 59
  24. Straka and Ramer 2010, 61
  25. Straka and Ramer 2010, 59-61
  26. Kemper 1941, 10
  27. Straka 2014, 106
  28. Walker 1966, 242
  29. Straka 2014, 106
  30. Straka 2014, 106
  31. Kemper 1941, 8
  32. Walker 1966, 242
  33. Kemper 1941, 8
  34. Kemper 1941, 8
  35. Walker 1966, 242
  36. Svedelius 1875, 32
  37. Svedelius 1875, 30
  38. Straka and Ramer 2010, 61
  39. Svedelius 1875, 30
  40. Kemper 1941, 12
  41. Overman 1854, 104
  42. Kemper 1941, 8
  43. Kemper 1941, 8
  44. McVarish 2008, 263
  45. Straka 2014, 107
  46. Kemper 1941, 14
  47. Straka and Ramer 2010, 61
  48. Straka and Ramer 2010, 61
  49. Kemper 1941, 14
  50. Kemper 1941, 14
  51. Straka and Ramer 2010, 61
  52. Kemper 1941, 14
  53. Kemper 1941, 14
  54. Svedelius 1875, 41
  55. Kemper 1941, 14
  56. Kemper 1941, 14
  57. Straka and Ramer 2010, 61
  58. Kemper 1941, 14
  59. Straka and Ramer 2010, 61
  60. Kemper 1941, 14
  61. Straka and Ramer 2010, 61
  62. Straka and Ramer 2010, 61
  63. Straka and Ramer 2010, 59
  64. Kemper 1941, 16
  65. Straka and Ramer 2010, 61
  66. Kemper 1941, 16
  67. McVarish 2008, 262
  68. Straka and Ramer 2010, 61
  69. Straka and Ramer 2010, 61
  70. Kemper 1941, 16
  71. Kemper 1941, 18
  72. Svedelius 1875, 51
  73. Straka, 2014, 107
  74. Kemper 1941, 18
  75. Straka and Ramer 2010, 61
  76. Kemper 1941, 18
  77. Kemper 1941, 18
  78. Straka and Ramer 2010, 61
  79. Straka and Ramer 2010, 61
  80. Wagner, 2008
  81. Svedelius 1875, 52
  82. Straka and Ramer 2010, 61
  83. Walker 1966, 242
  84. Straka and Ramer 2010, 61
  85. Svedelius 1875, 81
  86. Straka and Ramer 2010, 61
  87. Svedelius 1875, 58
  88. Kemper 1941, 21-22
  89. Kemper 1941, 20
  90. Kemper 1941, 8
  91. Svedelius 1875, 69
  92. Straka and Ramer 2010, 60
  93. Kemper 1941, 20
  94. Kemper 1941, 20
  95. Straka and Ramer 2010, 59
  96. Svedelius 1875, 80
  97. Straka and Ramer 2010, 59
  98. Kemper 1941, 22
  99. Kemper 1941, 22
  100. Svedelius 1875, 80
  101. Svedelius 1875, 81
  102. Svedelius 1875, 81
  103. Wagner, 2008
  104. Svedelius 1875, 82
  105. Svedelius 1875, 89
  106. Svedelius 1875, 89
  107. Svedelius 1875, 89
  108. Svedelius 1875, 89
  109. Svedelius 1875, 85
  110. Straka and Ramer 2010, 61
  111. Kemper 1941, 24
  112. McVarish 2008, 262
  113. Svedelius 1875, 85
  114. Wagner, 2008
  115. Wagner, 2008
  116. Svedelius 1875, 84
  117. Kemper 1941, 24
  118. Svedelius 1875, 85
  119. Svedelius 1875, 85
  120. Svedelius 1875, 87
  121. Svedelius 1875, 87
  122. Straka 2010, 61
  123. Williams 1989, 341-342
  124. Journal of the United States Association of Charcoal Iron Workers 1885
  125. Fernow 1882, 21
  126. Straka and Ramer 2010, 58
  127. Straka 2014, 105
  128. Straka 2014, 106
  129. Walker 1966, 121
  130. Straka and Ramer 2010, 60
  131. Straka 2014, 105
  132. Straka 2014, 111
  133. Straka and Ramer 2010, 60
  134. Straka and Ramer 2010, 59
  135. Straka and Ramer 2010, 61
  136. Straka and Ramer 2010, 59
  137. Straka and Ramer 2010, 59
  138. Straka and Ramer, 2010, 59
  139. Straka and Ramer, 2010, 59


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