I’ve read a little about what made for a good powder. In the not too distant past, it was a closely guarded secret, in fact. Part of the magic is the quality of the charcoal. Certain species of wood are better than others, charcoal made from willow for example, was said to be superior.
Even after the advent of Smokeless powders, there were differences in quality. My uncle spent some time on an all expenses paid trip to Europe in the 1940s, and said it was extremely difficult to determine where the firing was originating, the Werhmacht had very good smokeless powder for their firearms, while he said the stuff the Ami had was about as bad as the old black powder. “Good enough, and plenty of it” I suppose, but I could tell he was not happy about that situation years later. Wonder what the difference was?
Black powder does not Detonate. It Deflagrates.
https://www.thoughtco.com/explosions-deflagration-versus-detonation-607316
Other than that error, the article is pretty good. I haven't shot blackpowder in a rifle or pistol in a long time. I was getting pretty accurate with my 45 cal. flintlock.
Mostly now I use it for my 1 in. bore cannon and my 2-1/2 in bore Coehorn mortar.
By whom is it believed?
One of the cardinal rules of journalism is to use the passive tense only infrequently and NEVER in the lead.
In order to burn coal or wood the oxygen in the air must move to the vicinity of the fuel. The interior of the wood/coal cannot be burned until the fuel around it has be burned away.
The reason that some chemicals detonate is that the oxygen atoms are within Angstroms of the carbon or hydrogen, etc., atoms with which they will combine. TNT, nitroglycerin etc., are good examples.
Approximately a liter of nitroglycerin will detonate in an instant to gases with a volume close to 650L at 0C and 1 atmosphere of pressure. If you assume a gas temperature of 500C the volume is near 1200L.