When I made my first mortar (1974-75) it finally came time to shoot it - JULY 4th 1975 - within a few miles of the bridge between Lexington and Concord - on THE 200th anniversary of the first shot heard 'round the world.
I had powder but couldn't find fuse anywhere! What to do? Make it. Mixed a slurry of water and powder and soaked paper in it - let it dry.
Testing was ok - it sputtered a bit but burned at a controlled rate.
Next day we took it out and fired it on THE 4h.
OOOOOPS. The paper had dried out a bit more - instant ignition! GOOD thing that I was wearing ear protection!