I too am very glad with Kronckew's explanation on early black powder.
I just wish to add that at the beginning from ca. 1300 to 1500, which we call The High- to Late-Gothic period,
it was furnished as a very fine meal powder in wooden barrels bound by willow staves and carried in leather bags and thus could easily unmix by transport agitation and get highly hygroscopic thus turning into less effective mixtures and easily getting get wet.
Saltpeter, e.g., mainly came from the animal urine on farm walls. Some 600 to 500 year-old and earlier barrels in my collection and in others still continue to hold their old loads.
The details are from Bartholomäus Freysleben's
Inventarium Büchsen und Zeug, cod.icon.222, ca. 1495-1500, fol. 70v and 71r, an armory inventory for the then King Maxilimilan I.
Best,
Michael