I can see the logic of making the barrels like flour barrels, with the willow bands or some other flexible wood, because you could knock the bands off without causing sparks. It wouldn't matter if there was a metal chisel or screwdriver placed under the band and hit with a hammer, and the gunpowder would be lighter than liquids, so it wouldn't need the stronger metal barrels or bands.
But how did one deal with those pictured with metal bands? Were there special tools for opening them, or did they not spark just because... they didn't spark?
I've wondered the same thing about modern tins of black powder, but I figured aluminum or whatever they're made of must not spark like iron or steel. A period barrel with iron or steel bands, being opened by the nearest screwdriver with an iron or steel point, seems to be a risk for disaster. Unless those are some other darkened metal or some other metal was used in the opening tool...
What risk was there of sparks, from iron/steel against iron, or iron against another metal, or two other metals? Maybe I'm worrying too much even about iron against iron.