Sealing caps and nipples
Actually tested this several years back (posted in an old thread). Capped an unloaded cylinder , dripped some candle wax to fill up the area around the nipple, half submerged in a dish of water with caps down. All cylinders leaked.
Looked like the candle wax contracts as it cools.
Two places nipples leak, at the threads and under the caps.
Tried some primer sealer (Markron I think) around nipple and around caps. All cylinders leaked.
Used some beeswax mixed with just enough neetsfoot to make it soft enough to get it where it needed to be. packed the area around the caps full to make sure the threads and caps were sealed. Left in water 15 minutes. No leaks.
Loaded a cylinder, capped and sealed with beeswax (as a test) and left set 2 weeks. 3 caps fired fine. 3 didn't. Recapped those three and they fired o.k.
A real mess to clean up. All the beeswax turned to black gue.
So looks like, short term, beeswax will seal a cylinder, but if loaded very long the oil from the beeswax leaches up into the caps. How long? Didn't check that as the cleanup was such a mess I lost interest in further testing.
Oh, I might as well mention that I often resize caps as I like to have a tight fit.
Had a couple I thought were cracked, so I dropped them in a cup of water for a couple hours to dud them. Happened to notice nothing was really dissolved so left them overnight. Still wasn't dissolved. Dumped the water and set them in a corner of the cabinet for a couple weeks to dry out (dry climate here I might add). Capped an unloaded cylinder. All popped off and sounded o.k. Go figure. OYE