I made some charcloth today in a tin very similar to a sours tin. Poked a very tiny hole in the top w/ a finishing nail and tossed it in the fireplace and forgot about it. About and hour or so later I pulled it out and let it cool and had some very nice charcloth made from 100% cotton cloth squares. The type typically used for swabbing firearms' barrels. I never watched or waited for smoke or paid attention to whether or not it caught fire or if it ever even smoked at all and I got some very nice charcloth. I guess the point here is that there is no need to try to make an exact science out of it. It's really not that tuff to make.