The Bog Iron Industry

How Iron was Made at Atsion by George F. Atkin

For over one-hundred years, ending in the mid-1800’s, the Pine Barrens of New Jersey, a wilderness then as now, was a major contributor to the iron industry.  Few people realize that during this time over thirty separate furnace or forge enterprises were located along its waterways.  Even fewer are aware of how the raw materials were obtained, or of the smelting process.

Research has failed to produce a site plan or drawing of the Atsion furnace although its location has been identified through efforts of the Indian Mills Historical Society.  The sketch shown here is not meant to be academic but is a qualified attempt to picture this furnace as it may have appeared during the iron era of Atsion.

Underlying soils of the Pine Barrens are rich in soluble salts of iron which are carried into stream and bogs by the ever-flowing springs.  Here, in combination with decayed vegetable matter and exposed to air, a chemical reaction takes place in which the salts are oxidized. The resultant iron oxide is deposited along streams and in bogs where, mixed with mud, it accumulates and becomes bog ore (a variety of limonite).  Here, then, is the first and most important material needed for an iron industry.

Iron Oxide emerges from stream –

Limestone, needed for flux, was abundant in the form of clam and oyster shells found in nearby salt water bays.  Fuel was everywhere.  Thousands of acres of timber surrounding these iron furnaces  were processed into charcoal and provided the last of only three raw materials used in the manufacture of bog iron.

Necessary, also, was a source of power for the furnace bellows.  Here again the streams, so numerous in the Pine Barrens, were utilized.  A furnace site was chosen along one of these streams where a high rise of ground, or bank, was in close proximity.  The bank would afford as easier means, by way of a trestle, to charge the furnace. 

Iron ore was “mined” in the bogs and brought to the furnace bank in shallow draft boats.  Here it dried, hardened and was crushed by water-powered hammers before being placed in the furnace.  Also on the bank was a “bank-house” where all raw materials were weighed and prepared for the blast.

The iron furnace structure was usually made from Jersey stone although brick or other rock was sometimes used.  Built like a flat-top pyramid it stood twenty feet high, on a twenty foot square base.   Arches on all four sides allowed entrance to the hearth.

The iron furnace at Atsion as it may have appeared.

Inside was the firing chamber, insulated from exterior walls by brick, sand and mortar.  This chamber, from a small opening at the top for charging, gradually widened until reaching the “bosh”, its widest point (six to nine feet), about six feet above the hearth floor.  Below the bosh it narrowed sharply, leading to a pit known as the crucible.  The firing chamber was lined with refractory material, usually slate or firebrick.  Water-powered bellows forced air into the area just below the bosh by means of a pipe pre-set through the furnace wall.

The furnace was usually “put into blast” late in March, when streams were free of ice, and continued uninterrupted until the winter freeze.  During this time, furnace workers labored twelve hour shifts, seven days a week.  There were no holidays or vacations unless a “Puff-out” occurred (sudden cessation of blast) or a fire destroyed one of the adjacent sheds.

After initially “drying out” the furnace with a full charge of charcoal, alternate layers of charcoal, iron ore and flux were added continuously.  Molten iron, being heaviest, would settle in the crucible while slag, separated by, or sometimes mixed with flux, would float to the top.  Usually twice a day the iron and molten slag were drawn off through separate tap holes.   The slag, after cooling, was carted away in wheelbarrows and often used in improving the dam or constructing roads.

Molten iron was released through the bottom tap hole and flowed into a series of trenches forming “pigs” or was ladled into molds for cast products.  Pig iron later found its way to a forge – often located nearby and a part of the same iron enterprise – where it was further smelted, refined and hammered into wrought iron.  Out of the forge came products such as wagon tires, tools, nails, and horseshoes.  Cast iron from the original furnace blast was used for stoves, sash weights, firebacks and other products not requiring the strength afforded by more refined iron.

For over a century the iron industry flourished in South Jersey.  Forests re-grew and once again furnished  charcoal for the fires while bog ore would replenish itself every twenty years or less.  Even in times of drought the streams continued to supply sufficient water power for the bellows.  In spite of long hours and many hardships there never seemed to be a lack of manpower – ore raisers, boatmen, lumbermen, colliers, teamsters, banksmen, fillers, hearthmen, guttermen, moulders, pattern-makers, blacksmiths, and warehouse men all lived in the village with their families.  Often three generations of the same family worked together at the same furnace or forge.

However, bog-ore, charcoal and the Pine Barrens furnace were not the ultimate in manufacturing of iron.  Often, two and a half tons of bog ore and nearly a half ton of charcoal were required to manufacture one ton of iron in the primitive furnace.  Richer ore and a more efficient fuel in the form of coal, discovered in Pennsylvania, sounded an end to South Jersey’s iron industry.

Today the manufacture of iron is still located near the supply of mined ore and coal, while the smelters and convertors many times dwarf the old Jersey iron furnace.  But it is not without pride that a “down-Jerseyan” can relate to the once great industry of the Pine Barrens and know that the efforts an hardships of this era forged not only iron but a new nation.

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