I cook regularly on a wood stove. Lately it occurred to me that I could also dump a sealed container into the flames to make activated carbon ... which I did. To test the carbon I dumped some iodine to colour the water - then tossed in a lump of the charcoal (crushed).
After a while the water was clear - which is perfectly fine. The trouble is, a layer of charcoal 'scum' formed on top of the water. I can get rid of the scum by passing the water through a filter - perhaps sand, or even fine cloth.
Is there a way to prevent the charcoal from carrying impurities that form the scum in the first place?