Iron Age Life: Experimental Archaeology in Denmark

Day four

         

Opening the charcoal pit.

During the night the storm had passed leaving a chill in its wake.  The day crept in cold and the feeble sun was not able to banish thoughts of winter.  It was an ominous start to a day that promised to be a memorable one.

            Kim, upon his arrival, was impressed with our efforts.  That furnace, if it would last today would last four or five smelts.  The length of the smelt would be determined by how much charcoal we had produced.  The step to determining this was to break open the charcoal pile.  Just like two days previously, the families and museum visitors gathered around.  This time I held an old broken paddle in my hand to push the dirt away.  There is a chance, Kim smiled, that the fire hasn’t gone out and it may flare up when it gets access to air. 

Timidly, I began pushing away the dirt.  Under the layers of soil there is something solid.  The sod had baked solid, forming a solid dome. The sod brick is hot to the touch.  If I’m to be burned, this is the moment.  Instead of engulfing flames there were blackened rocks and beneath these blackened wood.  The ore and charcoal were still hot to the touch, but everyone touched them anyway and passed them around.  From all sides of the charcoal pile hands reached out to pull the dirt shell away.  Many of the pieces of charcoal were still smoldering.  These were quickly extinguished or placed into the stack of the furnace.  The wood looked the same as when we had packed it in the day before except now it was shiny black.  Rings could still be counted on some of the pieces.  Almost all of the pieces of wood had been transformed; those that had not were taken to the communal fire for fuel.  We produced enough charcoal for our smelt and maybe for the blacksmith shop as well.  

Among the dirt and between the charcoal was the iron ore.  It was dark but iridescent; all signs were that the rust in the ore had been transformed into FeO4, a very good form of iron.  The ore was friable and considering we had to crush it again, that was convenient.  The ore needed to be crushed to be about the size of peas or hazelnuts, depending on whom one asked.  The crushed ore was placed into a small basket for transportation down the slope to the furnace.  Four of us set to work with blacksmith hammers on one of the rubber sledges.  As some of us set to work crushing the ore others put the charcoal into a separate basket.  A third group began the smelt.

We produced charcoal! In my right hand is a piece of charcoal and in my left is a piece of ore.

On the first day we set to work, Kim had built a tuyere of white clay.  It had spent the last few days drying in the protection of the forge.  Now it was inserted through the clay door made to fit within the portal at the base of the furnace trough.  The tuyere directs the air flow from the bellows into the heart of the fire.  The bellows were two hand powered bellows that pushed and pulled the air through the tuyere.  It was possible that this motion preheated the blast and increased the overall temperature of the fire.  Unfortunately, we did not have the technology to test this theory.  The top of the tuyere broke off half way through the smelt.  We were not pleased when the tuyere broke, but it mimicked tuyeres found in archaeological deposits, and this was a pleasant surprise.     

Setting the bellows into the side of the furnace.

The smelt started by setting a fire in the furnace.  The fire burned for about an hour and a half until the smoke dissipated and was replaced by flame.  Then the work began.  The furnace was charged with seven handfuls of charcoal and five handfuls of ore.  This was done every fifteen minutes for about four hours.  The bellows were pumped from this point until the end of the smelt.  For the first hour or so, the fire within the furnace would go out and need to be relit with a spark at the top of the furnace.  When a cloud cast its shadow, we could see the flames around the top of the furnace stack.   In the bright light of day the flames were invisible.

As the smelt came to an end, the innards of the furnace were spilled out to find the iron.

When the slag was tapped off a flaw in the furnace was revealed.  The bottom of the furnace was still damp and robbed the fire of heat.  The slag did not flow beneath the tuyere and at one point solidified in the tuyere.  Most of the slag solidified at the bottom of the furnace further cooling the fire.  The cooler temperature slowed the formation of iron.  It was decided to end the smelt early.  The visitors to the museums and the Iron Age families were gathered to see the iron bloom emerge.  Using a metal rod, Kim pounded the clay, breaking down the door, shattering the tuyere, and letting out the slag.  The slag flowed down the broken tuyere like a red black river.  Someone remarked it looked like lava as the slag, burning charcoal, and pockets of iron poured out of the furnace down the trough.  The radiant heat certainly felt like a volcano as I leaned over the top of the stack with an iron rod to break pockets of iron away from the furnace walls.  Once the material was loosened from the side and filled the trough, the delicate work of picking out the iron began.  Danish and English shouts rang from each side. 

“Try that one”

“There’s one”        

The two large rocks are unproccessed iron ore with a piece of slag on top and a piece of iron at the base.

As midwife to the furnace, it was my responsibility to lean over the trough of red-hot afterbirth to draw out the iron.  A suspected piece would be picked up and squeezed in the grip of the iron tongs.  If the pressure of the tongs would give with a frighteningly loud crunch, then it was slag and not precious iron.  The cooler temperatures had kept the iron from forming one solid bloom; instead there were many small pieces of iron.  A small pile of iron pieces grew until there was about a kilo of iron.  There was one step left in the process: consolidating the bloom and expelling the rest of the slag from the iron. In some smelts this is done by breaking down the wall of the furnace and using it as a forge.  Kim wanted to keep the furnace we had constructed intact for future use.  Thus, we moved into the blacksmith’s forge.  The hour was late when we started.  Kim showed me what to do before he had to depart for home.  When consolidating a bloom, the smith had to maintain the fire at white-hot, also known as welding heat.  At this stage the iron becomes sticky and attaches to other pieces of iron.  We attempted to consolidate the bloom but with little processed after an hour, it was determined that the bloom should be taken back to the United States and consolidated there.  There were people who wanted to work in the forge who had not had a chance over the last few days.  We were to leave early the next morning and it did not seem fair to ‘hog the forge’ when many people had projects they wanted to complete.  

Our first piece of iron.

In small groups, or alone, our Iron Age family made our way up to the Mulithouse to wash and change out of our Iron Age clothes.  Our train was to leave at 7 the next morning and there was no time then to return our borrowed wardrobe.  Dressed in ‘civilian clothes’, as we joked, we made our way back to spend one last night in the little village and the long house.  We exchanged parting gifts with the families with whom we had shared the past few days.  Together we all laughed, ate, and watched the sun set.  Everyone seemed hesitant to go to sleep as though going to bed would signle the end of this wonderful adventure in “Never-Neverland”.  It was the smell of the straw from our bunk that I remember best from that night.  In the morning I slipped down to the sacrificial bog to leave one last offering before the skull of a horse, a piece of iron we smelted.  If this had all been a dream, at least some day if an archaeologist ever excavated the bog they would know what we did.  Too soon the morning had come.  Too soon we were at the train station boarding on the line that would take us to the airport.  In those quiet moments as the train glided along its rails, each of us said a silent farewell to Denmark and the Iron Age life we briefly lived.                  

 

The bog.