Iron Trails

Charcoal Production at Hopewell Furnace

Article by Tom Straka and Wayne Ramer
Photographs by Pat Straka.

The forests around Hopewell Furnace would have many charcoal pits being constructed and burned at the same time. Here notice a pit burning with just a small amount of smoke escaping from a few vent holes. In the background is a pit under construction without its covering. Notice is has three tiers and might contain 25 to 50 cords of wood. The demonstration pit at Hopewell is smaller at about 5 to 6 cords. The tier is called the foot; the second tier is called the waist; and the top tier called the head. Credit: Charcoal sketch by Artist Susan Styer, using charcoal from one of Hopewell Furnaces' charcoal pits.

The article last issuedescribed a typical Pennsylvania iron plantation. There were over 250 iron works in the colonies at the time of the American Revolution and they produced about one seventh of the world's iron output. This production was centered from Southwest New York to Northern Maryland, and included Eastern Pennsylvania and Hopewell Furnace. The American iron industry was entirely fueled by charcoal until the mid-1800's and charcoal continued to be a major iron furnace fuel for the rest of that century. If you visit Hopewell Furnace you will notice charcoal played a huge role in the plantation. Typically, over one half of the work force for an iron plantation was charcoal production-related. Hopewell Furnace would consume as much as 800 bushels of charcoal per day.

A charcoal pit required constant tending. The collier could tell by the amount and color of the escaping smoke if the charring was progressing at the right pace. The small charcoal pits at Hope-well take a week to burn through and volunteers must remain on duty 24 hours a day. Here the collier is on top of pit and "jumps the pit" to ensure the seal is tight and pockets have not formed. Credit: Charcoal sketch by artist Susan Styer.

When you tour Hopewell Furnace you can't help notice the importance of charcoal. Iron making requires three ingredients: iron ore, a flux (usually limestone), and charcoal. Of the three, charcoal was the most expensive. The other two could be mined, but charcoal had to be made from local timber and a time-consuming, delicate process. The charcoal house is one of the larger buildings you'll see; next to it will likely be a charcoal wagon filled with charcoal. Periodically Hopewell Furnace produces its own charcoal. Volunteers construct an actual charcoal pit and produce charcoal using exactly the same techniques of colonial times. There are only a few sites across the country where charcoal is still produced in the traditional manner. Hopewell Furnace is the sole location within the National Park System you can see a demonstration of this manufacturing process. It is authentic, down to the smell, smoke, and colliers (charcoal makers) who will explain the process to you.

The collier had to live near his charcoal pits and constructed a small hut for the purpose. His children or wife might bring him food each day.

Charcoal is made by partially burning (carbonizing) wood. Controlled combustion results from regulating the fowl of air to the burning wood. Water vapor and volatile gases from the wood are burned off, leaving a carbon residue called charcoal. The wood is reduced to about half of the volume and a quarter of the weight, making it easier to transport. Charcoal had its advantages. An ample supply existed in Pennsylvania. It produced a higher quality iron than coal and a charcoal iron furnace cost half the capital of a coal furnace. Charcoal is a concentrated head source (producing much more heat than an equivalent weight of dry wood),

Most of Hopewell's employees were woodcutters. Land controlled by the Furnace was clearcut on a 30-year cycle. Woodcutters were paid by the cord, but also for hauling distance and quality. Two sizes of wood were cut: lap-wood that was 1 ½ to 4 inches in diameter and billets that ranged from 4 to 7 inches in diameter. Both were cut in 4 foot lengths with a bias in the end so that they'd slant inward in the woodpile and form a heap. Most billets came out of tree trunks and most lap-wood from the branches.

There was no argument at Hopewell over which wood produced the best charcoal, as every acre was cut clean and wood ended up in the charcoal pit. Hopewell Furnace would consume as much as 800 bushels of charcoal per day when it was "in blast." This equates to as much as an acre of forest cut to produce one day's worth of charcoal. It took about 200 acres of forest to produce a year's worth of charcoal for a furnace. The charcoal making process involves:

• Clearing and leveling the ground for the hearth, usually in a 30 to 40 foot circle.
• A triangular chimney with a small opening is built with lap-wood.
• Tiers of billets are carefully laid against this chimney; all slant slightly inward. All small spaces are filled with lap-wood.
• The pile is covered first an inch of leaves and then with about 4 inches of dirt (or old charcoal dust).
• The chimney is filled with kindling and red hot coals from the cooking fire are used to ignite the pit.
• Once ignited, and the chimney covered, the pit was carefully watched and tended. The color of the smoke coming from the pit indicated the quality of the charring or air leaks.
• Once the pit "comes to foot" or is fully-charred, it is carefully raked out.

A small charcoal pit ready to be covered with leaves and old charcoal dust. Notice the leaves and charcoal dust ready to be used to cover the pit.	As the charring process continues, pockets develop in the pit; the collier walks the pile, called "jumping the pit' to locate them. Any soft spots are filled in with more wood. This is the senior author jumping the pit during a recent demonstration.
The volunteer colliers take turns on the overnight shifts. This night shot of a charcoal pit shows the smoke is indicating proper charring. The collier watches both the color and amount of smoke coming from the pit, even the shape of the steams of smoke can indicate too much venting. The word charcoal pit is a misnomer; a charcoal pit is entirely above the ground and incudes the hearth and the wood pile.	Once the charring process ended, great care was needed to ensure the fire was actually out. The charcoal was then transported by teamsters to the charcoal cooling shed. The charcoal wagon above sits in the cooling shed next to the charcoal house. Once the threat of reignition was past, the charcoal was moved into the charcoal house for storage.

Charcoal was fundamental to Pennsylvania's early iron making industry and Hopewell Furnace illustrates a fascinating aspect of American history. Be sure to watch the video on charcoal making in the visitor's center. It highlights a fuel that had a huge impact on American forests.

Authors: Thomas J. Straka is a forestry professor at Clemson University in South Carolina (and a volunteer collier at Hopewell Furnace) and Wayne C. Ramer is the master collier at Hopewell Furnace.

Additional Websites:

http://www.nps.gov/hofu/historyculture/charcoal.htm

http://www.nps.gov/nr/twhp/wwwlps/lessons/97hopewell/97visual2.htm

http://www.oldindustry.org/Phttp://www.oldindustry.org/PA_HTML/ Pa_Hwell_Charcoal.htmlA_HTML/Pa_Hwell_Charcoal.html