Making Charcoal

Friday 6th March 2015

One of my most ambitious projects is to make a bronze sword, which involves learning a whole bunch of new skills. My original plan was to get tin and copper ores, and smelt them to refine the metals, but after a visit to Geevor tin mine I realised that I'll need at least a tonne of rock, so I'm going to buy tin and copper metal and start from there.

So my first task is to make charcoal to make the bronze.

What's charcoal?

I didn't really understand what charcoal was until I started researching this project. Essentially it's wood that's been heated in the absence of air, to remove all the water, oils and other volatile chemicals, and leaves pretty much just carbon. The absence of air is the really important thing here, because otherwise it just burns.

Because all the water and stuff has been removed, it burns massively hotter than wood, hot enough to melt tin and copper and make bronze. I only need a small amount to make a sword, so I found a method that you can do in an afternoon, and Rob and I got stuck in.

Here's what we did, and you've got to guess what we did wrong.

A simple kiln

First we acquired a 200 litre drum and a 60 litre drum and cut the tops off with a jigsaw (below, left), which is a legitimate use for that tool. We cut small flaps into the bigger drum to allow air to get in.

Both drums had previously contained engine oil that we didn't want in the final charcoal, so we lit fires in them both.

While they were cooling down, Rob sawed up some dry logs (below, middle) and we packed them into the smaller drum so tightly that we could turn it upside down without them falling out (below, right). This is important.

So far so good.

Cooking the wood

Next we turned the small drum upside down and placed it in the middle of the big drum. Then we packed sawn up pallets all around the edge of the big drum (below, left) and set light to it. We kept feeding the fire and let it burn for two hours (below, middle).

This heats the wood in the smaller barrel in the absence of air, which turns it from wood into charcoal. After two hours we let the fire die out, and let the barrels cool down until we could touch them (below, right).

Then we tipped the large barrel onto its side and carefully pulled out the small barrel, which was now full of charcoal!

The charcoal was still really hot, so we put a lid over the barrel and left it for a few hours to cool down.

Cocking it up

Spotted the mistake yet?

When we came back to check on it three hours later, the charcoal was on fire!

Because we were so excited we removed the small barrel too early and a stray ember from the fire must have landed amongst the charcoal, which was nice and hot and suddenly had access to lots of oxygen.

Oops. But it was obviously good charcoal because it was blisteringly hot.

So we've all learned an important lesson today here folks: you can't hurry love. We'll be making another batch soon, and we'll be much more careful this time. And we salvaged one bag of usable charcoal before it all burned.

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