Here's a carved foam bodywork section being prepared for glass lay-up, or more accurately, being repaired after cracking along a particularly thin section. You can see the 'weld' line of foam curing behind the two cans holding things in place. Once this is set it'll have glass laid up on the outer surfaces and be strong enough to handle for finishing.
Never mind what this section is, the question is 'Why has one of the cans got a latex glove over it'? These are the two cans of PU foam 2-pack from which that weld line and all other joins in the foam slabs come. The Part 2 absorbes oxygen from the atmosphere and turns into glue. Covering the top of the can with the glove prevents this and means the lid will unscrew next time, as oposed to not. Wipe off any liquid from the screw top after use and clean off the glue that does appear with a wire brush occaisionally to make sure.
Another tip. Lots of people don't like powdered Latex gloves but they are Essential wear for handling epoxy resin. This has such a low molecular weight that it goes through unpowdered Nitrile gloves. You don't want either Epoxy resin or uncured PU foam touching your skin. Two pairs of gloves recomended for safety, although a pair of Latex over a pair of Nitriles is a solution for people allegic to Latex or the powder.