After a while of procrastination (always a fun pastime :p ), Mark and I decided to go wandering for a drum to make charcoal in. Eventually we found a badly rusted 55 gallon drum and lugged it the mile home. We didn't find a smaller sealed drum which could sit inside it for a retort, so we went with the direct method.
Put the drum right side up, load it with logs, put some lighter fluid on it (charcoal lighter if you want to do it in style, but paint thinner works perfectly fine :) and light it. When it's burning good, put a piece of sheetmetal on top as a lid - leave a gap so it can still burn - and pack some dirt around the bottom air holes to restrict airflow.
I suppose I should've taken some more photos inbetween, but what I did is nothing that can't be said. After an hour or two (while keeping the airflow restricted adequately; you want it to smoke a bit, but don't smother it; if I do ever upload any pics of this period they won't be very smoky because I don't want to risk a citation or something..) it'll be burning down pretty good, maybe 1/4 of its previous height. This will go down even more as it finishes, and quite simply it's because wood is actually a lot of water and not much carbon, so it loses a lot of volume - and also as it breaks up it compacts tighter than the logs it used to be. When it's just about finished there will be only a few logs still charring (burning with a flame or smoking). Depending on your patience and want of unburnt leftovers (versus your want of charcoal - the longer it sits in there, the more it burns down), you can stop it at this point. If my drum weren't rusted to all hell, I'd put a lid firmly on top and fill in all the air holes. But since this thing is a big seive, I don't have that liberty. So what to do? Tip it over and shovel out the still-burning charcoal! It's a hot job but it works.
These three buckets are from one burn. No idea how much weight there is there, but it is hot and needs to be kept from burning while it cools. To do this I cover it with sand, then later when it's cool I sift the sand and ash from the charcoal (a dusty job!!) and package the finished charcoal.
Here are the leftover logs that didn't burn up. The first burn this evening (yes I did two!) I put thick logs on the bottom, they never got very hot for very long so this is the result. These burnt ends (brands) can be thrown in with the next charge, so in the mean time they just take up space.
This is from the first burn, about 8x14x18" pile. That black spot you see on the side, yep that's char. Seems one (or more) of the coals wasn't completely cool and it ignited the box! A little water got rid of that, but beware of this fire hazard. If your burn drum can be nicely sealed up, leave it to cool for a good number of hours before extracting the charcoal so this doesn't happen.
Here I was burning down oak - hardwood is good for pretty much everything - but it applies to any wood. Soft woods have a more open structure so make weaker charcoal. I don't know if they would take longer or shorter, but a burn shouldn't be timed, it should be observed.