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I2ichmond t1_iro50qc wrote

Reply to comment by taphead739 in Why, when you continue to burn ash, do the ashes eventually change from black to white? by genitalwaffles

Here to supplement with this: https://www.youtube.com/playlist?list=PLGnWLXjIDnpBVRqu5lz5JGaQxjPs7q3CJ

Watching these Primitive Technology videos on fire got me curious about all the different kinds of combustion we take advantage of. He has videos in that playlist where he makes a charcoal mound which is designed to burn wood only through the first stage so you end up with the leftover carbon, which can be burned all over again to produce much more intense heat. Charcoal is sort like refined wood (or refined organic tissue, in a broader and weirder-sounding way)

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Lurker_IV t1_irqmf93 wrote

Charcoal is pure carbon. The heat of fire without any available oxygen in the mound vaporizes any volatile compounds and burns them off leaving the carbon.

Charcoal fires can burn up to 100-degrees hotter than wood fires, iirc, which is why it is needed for metalworking.

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malastare- t1_irr13hd wrote

>Charcoal is pure carbon.

Not really. It still has some of those metals that end up as white oxides when you completely burn the charcoal, and it still has a decent amount of bound oxygen. The volatile compounds are mostly gone (with a bunch of the carbon) but all the trace metals are still there too. Some processes are able to remove some of them, with the goal being a result that retains as much carbon as possible, but burning even the best charcoal still results in non-carbon ash.

Coke (a slightly different process) has a notably higher carbon content, but even that isn't nearly close enough to "pure carbon" to be considered chemically pure carbon. It's better as a carbon source for steel and more expensive that charcoal as a heat source, but from what I can find, its still just shy of 90% carbon.

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