Nov 11 Making a charcoal kiln, by Sean By Tracy

Give me that hacksaw, I’m gonna make some charcoal!

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Back in the mists of the 1990’s I had a ‘spare-time’ job clearing trees and had a very bright mate who wanted to make charcoal. He rented some buildings on a farm where I had my yard. In one part of his buildings there was a derelict water tower that used to be part of the laundry in the main village of Steyning (in West Sussex). This was a riveted metal tower of about 8 to 9 feet diameter and 20 or so feet height, the metal was all riveted together so you can guess how thick it was and it weighed so much it had been left to sit there and rot. This mate of mine decided to use a section of this and set about cutting a charcoal kiln height ring out of the tower. It took huge amounts of the beech we were clearing off the Downs – left over from the 87 and 90 storms. He and some friends loaded it up, fired it the first time and promptly got a visit from the local fire engine (complete with attendant tea truck!) because there was such a pall of smoke from the kiln it drifted down to the village. Despite this he continued to load and burn several times and amassed large quantities of charcoal – he then wanted to sell it but was not content with just delivering the sacks to shops etc. No, he had the brainwave of making a ‘demonstration’ kiln out of a steel oil drum and set about the project of miniaturising his kiln so that he could show people at the local summer ‘Country Show’ held in the high street every year. I thought he just wanted to show what it looked like to make charcoal but no, he had to make it so it actually worked. Complete with a lid, chimney’s and feet the kiln was duly loaded with small chunks of wood and blow me down – it worked. In fact it worked so well we even thought of making more to sell as do it yourself charcoal burners.

Now conjure an image of fluttering calendar pages peeling away the years stopping around 2007 when the author had taken early retirement, bought a pipedream and even gone back to work. Having 10 acres of woodland in a beautiful semi ancient wood I formed the vision of becoming the head of an empire selling locally made charcoal. Now, in the intervening years, home grown charcoal has become more popular and when I looked to see if I could buy a kiln I met with a dearth of bits of kit. They were either too expensive to buy new – Internet advertised ones start around £800-900 and any second-hand ones seem to disappear before they are advertised. Enter the old galvanised water butt from the back of my shed. It had sat there since I bought the house back in 1980 and now had a rusted bottom and only contained bits of rubble collected for a future project. Turning it over after emptying the contents confirmed its parlous state and only encouraged the entrepreneur in me. Setting to with some metal snips I cut out the old bottom leaving around ¾” old money (19 – 20mm to you young whippersnappers) of the bottom to remain as the support for a lid. I got an engineering company to cut me out a 3mm thick lid to suit and cut up some old sectional metal and smokestack made from 2” (50mm) aluminium aerial pole. Getting a metal hole-cutter of 51mm  I mangling holes in the sectional metal. I managed to burn out my drill BUT, we had the makings of a kiln in the style of my since emigrated friend.

Come the weekend we stuck it in the back of the car and took off to the wood. Now our wood is on clay and if you want to make charcoal you have to be able to exclude air from the kiln, when clay gets warm it dries out and cracks. Not good for keeping oxygen out. So, finding some building sand I splodged a mix of leaf mould, clay and sand together enough to lighten it all up for the task.  Following the same principles we used back when I didn’t need a truss or hair dye I cut up tree limbs and loaded the kiln.

When all the bits are put together it looks like, er, an old water butt!

Selecting the site so that there wasn’t likely to be too much damage to surrounding trees or any rare orchids we scraped the ground sort of level and put it together.

Loading the bottom layer in a radial pattern with thin and slightly longer branches helps to allow the fire and air supply to move through the kiln. Stacking the wood in the way shown in the picture below allows you to leave a small space that goes from top to bottom of the kiln. This is used to tip embers, from a good fire, down in to the heart of the kiln. There are other methods used by the ‘professionals’ but this worked for us in the past and it works in my kiln too.

Leaving the top off the kiln we let the fire get going – lots of smoke and an ear out for the dulcet tones of the fire services.

When we did the first firing I was concerned that if I left the fire to burn for too long we’d get very little charcoal. So I put the lid on and sealed it off with the sand/loam/clay mix. It turned out I was far too previous and the kiln sat there smoking for quite some hours – I went back at 12 that night and again in the morning before work but when I opened it up the next weekend all we had was very dry, light, smoked wood.

The next Friday evening I unloaded the kiln, re-stacked it set it alight and left for 30 to 40 minutes before putting the lid on and sealing it up – almost the moment the lid was on the kiln chimney’s started doing their job. I left it to ‘cook’ returning later that night

I waited around until the smoke changed to an almost invisible steam – not wanting it to run amuck overnight I put four baffles over the smoke stacks to slow the process until the next morning. Returning and shutting it down we left it all to cool. Not being able to leave it until next weekend my wife Sarah and I snuck up to the wood later that afternoon and cracked the lid off to find what looked like perfect charcoal.

I’ve since unloaded the burn only to find that we must have shut it down just a bit too early – only the bottom third of the kiln has carbonised properly and the rest are ‘browns’ as they’re called. All part of the learning curve and for a first go at it I’m not too disheartened – be patient is a good motto with new skills. The kiln works, we know that, it should produce a reasonable amount of a decent quality charcoal; we’ve just got to get used to the time it takes to burn and fire it accordingly. I’m pretty sure that if we fire it with wood stored in a dryer place that may speed the burn time too.

Since I built this kiln I’ve found a company that I can get to roll the angle iron diameters needed for the top and bottom ‘rings’ of a Ring Kiln. I’ve got a fairly local engineering company who are interested in getting the sides cut and bent so there’s now a vague chance I’ll make a full 6/7’ diameter kiln next year – don’t tell the wife – on the drive at home.

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