I cut three square holes like this and when we burnt it was finished in 3.5 hrs but nothing was charred?
The char in the picture was from the first burn that was 2o hrs… All done.
Reply from Peter Hirst:
You need at least four of those holes, probably six, evenly spaced around the bottom of the outer barrel. Then you need secondary air holes, smaller but more of them, evenly spaced around the top. . The inner barrel has to be completely sealed, except where gas is allowed to escape under the bottom rim and the space between inner and outer barrel packed with small fuel, lit at the top before the lid and chimney are placed.
PEter
previously I had written him that we had successful char in a much longer period without these extra air vents. We only had 2 slits made with a grinder on each side. This gave the effect of a 20 hr space heater (IE.,in greenhouse). I don’t see that making more holes will increase the charring in the inside barrel. So we will block up the holes and continue with the 20 hr burner. I think this will be more useful than obtaining a quick char.