Your thinking of charcoal, which are chunks of wood converted into almost pure carbon by heating them above their combustion temperature in a low oxygen environment. He was talking about coal that was mined out of the ground. Plants from an ancient swamps that didn’t decompose, but were converted into almost pure carbon from millions of years of heat and pressure from being buried.

I suffered for years before finding out about SLS causing canker sore outbreaks. Switched to an SLS free toothpaste, and haven’t had a canker sore in years. Little advice for people still suffering from them though, rinsing your mouth out with peroxide, instantly stops the pain. Also no burning sensation like you get with a fresh cut. It also seems to shorten their duration too. Just be careful not to swallow any.