Page "Gunpowder" Paragraph 86

together with a mortar and pestle, perhaps for 24 hours, resulting in a fine flour.

Vibration during transportation could cause the components to separate again, requiring remixing in the field.

Also if the quality of the saltpeter was low ( for instance if it was contaminated with highly hygroscopic calcium nitrate ), or if the powder was simply old ( due to the mildly hygroscopic nature of potassium nitrate ), in humid weather it would need to be redried.

The dust from " repairing " powder in the field was a major hazard.