Hotmelt helps cork caulk tubes
Over the years I've tried nails, screws, plastic wrap, wire nuts—you name it—to seal opened nozzles. None of those items proved effective; after a few weeks a hardened mass of caulk, silicone, or adhesive formed in the nozzle. Finally I tried placing a dab of hotmelt glue on the opened end. To my pleasant surprise, the resulting airtight seal kept the nozzle's contents workable for months.
—Dick Powell, Corvallis, Ore.