Curious stone cannon

[kronckew]

Originally Posted by Jim McDougall

...I am wondering if possibly the gunpowder used in earlier times might not have been as potent as of course more modern types.
...

initially gunpowder was a mechanical dry mix of powdered sulphur, charcoal and saltpeter. much less efficient. vibration in transport would also mechanically separate the components to some extent. knowledgeable gunners would re-mix their powder, if they had time, on arrival at the guns emplacement. fine powdered gunpowder also readily absorbes moisture ands loses it 'strength'.

someone in the 14th c. finally figured out that wet mixing the components mixed the disparate chemicals more intimately, resulting in a more efficient bang for your buck (and was safer).

the mix was ultimately corned - formed into grains of various sizes, the grains were screened to standard sizes, larger sizes for cannon, smaller for muskets, smaller still for pistols and the finest for priming. space between the grains allowed for more rapid and even combustion. the grains, even the smaller priming ones, did not absorb moisture near as much as the fine powder. modern powder is usually made (since the 19c) with potassium nitrate rather than sodium nitrate, and is normally coated with graphite to cut down the risk of static sparking.

i recall someone from the period stating that a charge of 18 pounds of properly grained cannon gunpowder was equivalent to 300 pounds of the old powdered gunpowder.

for more detailed info, see

this linky