Making cartridges like this can be a lot of fun or a lot of tedious work. It just depends on tho you ask. I've done it myself to scratch that hysterical I mean historical itch, and they all went bang whether I used coffee filters or cigarette papers. I did not soak or treat the paper in KNO3 or any other chemical.
One word or warning before you buy a bunch of conicals or a mold is to check that you have sufficient clearance to get the cartridges seated in your revolver. A lot of repro guns have just enough room there to seat a round ball, some can seat a conical ok but not all can seat a semi-rigid cartridge like these. Not a hard mod to make to your gun if required but thought you might wanna know if you didn’t already. Had to find out the hard way myself, as usual.