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Building a Frame Saw
Forging a Copper Kettle
Making a pair of leather work boots
Forging and Fletching a Bodkin
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Wednesday, August 7, 2013

Hearth Steel

Ever since the days when I first began forging blades, I had the dream of one day using steel I myself smelted from ore as it was done thousands of years ago. As they say, 'It is the journey that makes the trip worth taking,' and it is the journey which I cherish most. Something about the mythic properties of those rocks mined from the earth draws me as much as the fires of the forge. While this is some ways off yet, I had a taste of what it means to make steel when I attended the Northern Wisconsin Hammer-in a few months back. Hosted by Scott Roush of Big Rock Forge, we built a smelter to run some local Tiger Ore abandoned along the railbeds bordering Lake Superior. While that smelt did not work quite as planned, we also built a smaller hearth furnace to reprocess existing iron and steel. In principle, a hearth smelt is rather simple, as is a fully fledged smelter. Despite knowing virtually nothing about either of these, I came away with enough to recreate the process in my own back yard. 

First, I had to find things to reprocess into usable material. I have an assembly of old circular saw blades, broken pairs of scissors, rusty razor blades, the bottoms of those small camp stove propane cylinders, silverware, an old hammer head forged half way to an axe, and some rusty clod on the end of a mild steel bar I dug out of a forest a number of years ago. Also (not pictured) I dug some barbed wire, old bolts and other assorted hardware, pipes, and things I am not certain how to classify from the ash pile built up over the course of 20 odd years.

While I did not capture most of the pit's construction, here is a little glimmer into how I approached it.

Simple as a hole in the ground lined with bricks and covered in ash, this is the furnace. Out to one side, a salvaged pipe directs air forced from a shop vacuum into the bottom of the furnace, placed at an approximate 45 degree angle a few inches from the bottom. In retrospect, I should not have used bricks with holes in them (leftover from the chimney to the house, circa 22 years ago) as the air blasts ash out of them and defeats the purpose of using it for insulation.

Because the old burn pile is so far away, I had to run about 500 feet of extension cords to get the air supply out there.

Up in Wisconsin, we made the cobb from a mixture of local clay, sand, and natural materials (peet moss, dried manure, grass clippings, etc.). I had only some silt from a creek not far away, and a short expedition through the forest to its banks yielded enough for the project.

This was by no means the best possible thing to line the bottom with, but it was better than nothing. In the end, it mostly melted together and left a glassy plate on the bottom of the steel.

As with all furnaces and smelters, the flames required a sacrifice to bless the steel with success in the smelt. I placed a shard from the perpetual-WIP Persian dagger I started years ago that broke at least three times. The tip went in to fan the flames as green wood preheated and cured the furnace.

'Twas a hungry flame.

To help ensure the carbon content was high enough, although it would have been fine, I added a few pieces of stock 15n20 to the mix of Franken-fodder.

To fuel the furnace, I used natural all hardwood charcoal found at the friendly neighbourhood hardware store. If you are going to try this, be aware that it needs to be broken into pieces the size of your thumb, not the fist sized hunks it comes in.

Forcing air through the tuyere (air supply pipe) sends sparks flying into the air, which is unfortunately much more spectacular at dusk than the middle of the afternoon, but I love this picture. Small bits of charcoal are being shot out of the flames like a miniature volcanic eruption.

Once the sacrificial scrap steel was consumed in the flames and the charcoal supply at an end, I cut the air and let the inferno subside. That blackened mass on the left is the end of the tuyere where it melted and cooled from the air rushing over it.While I am unsure how hot it actually burned, it was around 2700 degrees (F) and far too hot to stand beside. On the other side, it cooked hotdogs in 20 seconds flat.

And finally, the yield. A nice fist sized hunk of steel, dense as can be and with minimal strange geometry ripe for inclusions when consolidating. I am yet to weigh it or cut it open, as I have been operating in a shop without power until only a few days ago.

This process opened many doors to me, both in the direction I would like to move as a bladesmith and in ideology of how I see and interact with the world. Although I may not be able to smelt down ore into bloom, I can start to reclaim the wreckage of humanity.

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