Resealing Caulk Cartridges
I find that I have a better chance of sealing a partially used caulking cartridge if I stick a plastic container on the end and fill it right up with caulk. A 35mm film can was my previous choice, but now that my photos are digital, I use whatever's handy, like this plastic box cap. Securely wrapping the mess with aluminum foil completes my sloppy but effective reseal job.