Primitive Tech – Clay, Charcoal and Water

by Jamie Hall on April 10, 2012

I’ve been at the site a couple of times since my last post, and while it’s by no means a workshop yet, things are starting to take shape. The first step was utilising some containers that are already onsite. There are two types of barrel – blue type-2 plastic, and metal oil drums. The former were no real challenge. With a small joinery saw, it was easy enough to chop them up. I cut one down its long axis, and cut the top off another.

Weathering Pit

The half barrels are for making weathering pits for clay. The idea is to take clay out of the ground, and allow the weather to repeatedly wet the clay and dry it out, which should break up the particles into a more uniform size. Presumably this works well during winter frosts, but that’s a long way off (it’s April now). I’m hoping to keep these weathering pits stocked up, and probably leave one untouched until next year. As I’m not making fine pottery, I’m happy to start using the clay immediately. It probably wants a bit of washing, but it seems extremely plastic – it came out of the ground in slices, and the areas of lower clay content were really clear to see. They were a darker colour, and came away like thick brown cream from the solid mass of the red clay. Sorry, that’s the best description I can give!


Another possible avenue is washing the clay aggressively, and decanting and filtering the claywater. To do this, I’ll need water, which the other barrel was used for. As we have no mains water or electricity onsite, we’ve got to be a bit more imaginative. I’m bringing some water down in 25l barrels, but that won’t last long once I start washing clay and wood ashes. For this reason, I’ve made a crude rain-catcher, using a tarp and some rope. I hate spending money, so I’ve thought very carefully about this. The plastic tarp cost me £5, and measures 2m by 3m. Most importantly, it already had eyelets. The rope was a further £5; about a third of the price it would have cost me at a large store (which goes to show the benefits of using small shops, and asking for trade discount). As rope really isn’t as cheap as I expected it to be, I’ve done something I’ve never even thought of before. Being a boyscout.

What I mean is, I’ve been learning about tying knots. This has never seemed remotely useful before, but now I’m really quite intrigued by it. I found a great website, Animated Knots by Grog, which covers knots for all kinds of uses, including scouts, rescue and fishing. There are also iPhone and Android apps that you can purchase through the site. Luckily, I have mobile wi-fi and a tablet PC, so I can usually access the website onsite. My needs were for load-bearing knots; the tarp has been done with bowline knots and figure-of-8 knots. Nothing too fancy, and no doubt I’ll learn better knots for each task as I go. One thing I did do was properly finish the ends of the ropes, something called whipping.


As you can see in the photo, the rain-catcher is fairly simple in design, and should come down in about 10 minutes, if needed. All of the rope should then be reusable, as will the tarp. I used the barrel with the top cut off for the water butt. Although the surface area of the tarp is no more than 2 square metres, if it rains, there is a steady trickle into the butt, so I’m happy. Ingeniously, I’ve used a weight on the lowest part of the tarp, so that even when the wind blows, the “spout” stays over the butt. Likewise, the tarp is suspended with a sort of crease in it, which makes it resistant to strong winds, as there is less area for the wind to use as a sail!

The final thing I wanted to do was charcoal. It will take time to build this up to being an economical process. This experiment was done in the rain, with wet wood, so it wasn’t the easiest of starts. The process of charcoal making is very simple, in theory. Heat pyrolises the volatile chemicals out of the wood, starting with water, and moving onto other substances, many of which are inflammable. Once these are gone, there is only carbon, ash and a few other traces left behind.


The biscuit tin (pictured), has four holes in the lid, to let gases out at the beginning of the process. In the initial stages, a white smoke was emitted – this is apparently steam, and other volatile gases. Once they have pyrolised off, the holes are stopped up with clay to prevent oxygen reaching the charcoal. As you can see, the attempt wasn’t terribly successful, although the bottom third of the tin did contain very good charcoal (see below). The reason for this is pretty clear – the tin was sat on top of a small fire bucket, which only heated the tin from below – the process had certainly started on the top layer, but was far from complete.

This method is hardly very primitive. Unlike a charcoal clamp, which houses the fire inside the “container” of soil and turf, this method is more like the modern approach, where an external heatsource is used. Still, it is useful to get an understanding of what happens with the wood. I’m hoping to do this on a larger scale, and eventually move up to a large clamp or pit method. That brings me to the one real failure onsite – the metal barrel.

The idea is to do the same as with the water butt, and take the top off the barrel to use it as a lid. I took a hammer and a cold chisel (bear in mind we have no electricity), hoping that it would be a simple matter of cutting along a line. It does sort of work, but I think my chisel is too small for the job. I was hoping to do this, and perform a much larger, more ambitious charcoal burn, but I’ll have to shelve the idea until we can do something about it. Maybe a better chisel? In any case, the metal barrels are pretty horrible inside, and might pose safety issues for cutting with an oxy-acetylene torch.


My next batch of plans are to repeat the charcoal method with the biscuit tin, and possibly even build a small pit (one of the owners is camping that night, so she should be able to keep an eye on it, if I do). If the weather is nice, I’d like to have a play with the clay, perhaps washing it, or seeing how readily I can make small crucibles with it. But I’ll only do that if the sun is shining. I’d also like to start establishing a hearth area, perhaps by prepping the ground with a later of clay, or some other material to stop the body of the hearth blending with the soil beneath. Another thing I want to look at is storing wood ashes, and washing them to produce lye. It’s actually the washed ashes that I’m interested in, but lye takes us in a different, and interesting, direction. That will probably need another barrel chopping in half across its width, and some kind of frame built to suspend half above the other. I’m hoping that a layer of straw, followed by a layer of sand, followed by a thick layer of ashes, will be an appropriate filter. Ideally, an additional bucket wants to be suspended above that one, from which a steady drip of water will pass through the ashes; I’ve read that adding too much at once can just wash the ashes through the filter materials.

{ 1 comment }

Albert A Rasch August 29, 2013 at 02:26

Find, beg, or borrow a 35 Gallon drum with a lid.
Poke 6 – 10 holes in the bottom.
Fill with wood pieces you intend to make into charcoal.
Take 55 gallon drum, and drive a couple pieces of 3/4 in rebar at 90 deg, at about a quarter to a third of the way from the bottom.
Cut a door to load fire wood near the bottom. If you have time/desire, put a good layer of clay at the bottom of the 55 drum, it will last longer.
Put your 35 drum into the 55 drum, leaving space all around. (It will be about 2-3 inches.)
Start you fire under the 35, and keep it fed until the pyrolyzed gases start to self ignite.
Watch out, it’ll get real hot! flames will shoot out the door, and up the sides!
You can feed the fire through the door, or drop wood down the sides.

After the first use, it will be safe to cook hotdogs, chunks of meat, and squirrels over the flames.

use common sense, watch out for combustibles, and you should be fine.

Be safe!
Albert A Rasch

Comments on this entry are closed.

Previous post:

Next post:

WordPress Admin