My problem is that if I leave powder in a flask for any period of time I'm likely to forget the grade of powder. Here in the States black powder comes in metal cans, is that the same as the bottles to which you all refer? I store these cans in metal ammo cans as a protection against flames but I'm mindful that they also create a hazard if the powder explodes. There is a reason why powder mills merely tack on the building's siding. When I owned and fired a civil war cannon (original 3" Ordnance Rifle) I left a goodly quantity of cannon powder in a dog house well away from the house.