I made charcoal in a clay pot by putting wood in it and heat the pot externally effectively making it like a retort. Previous methods of charcoal making directly heat the wood by burning a portion of it to create the charcoal. But this method applies the heat indirectly to the wood with it completely sealed off from oxygen. The wood successfully turns to charcoal on a small scale but fails to scale up due to the larger pot cracking during the firing and letting air in which burns the wood to ash. The theory is sound but more work needs to be done on the pot to stop it from cracking.