except inverting the container and latex caulk. The materials used to seal quality paint will not "dry out" like a wine cork. They should be kept absolutely clean, however. Latex caulk is particularly susceptible to some solvents found in acrylic paints. It also contains plasticizers that migrate very well, and may do strange things to the paint. The best modern secondary sealer, if you feel the need, is PARAFILM M. It was and is made for just this purpose. Stretch out a bit and wrap it around the top of the bottle, overlapping the cap/lid and the bottle itself.
Oooooh, I like the Parafilm M suggestion. I can get tons of that stuff! Thanks.
Thanks to life events, I have only recently returned to scale modeling. Now, I'm no chemist and don;t claim to be. I know doodly about stuff like plasticisers and solvent migration and other sundry "painty " things.
But, in going through my old paints, I found many bottles of enamel that had been stored upside down, per my usual habit, and are still useable after years. I can't say the same about the acrylics - some of them are un-usable. The results varied and I wish I had taken better stock as to what was good and what wasn't. But on the whole, the majority of them still had use left in them.
The only thing I can think of is that the enamel paint at the edge of the rim dried out enough to make a seal and prevent further degradation... which is what was found once the lid was off and in the end, is good enough for me. It is indeed important to keep the threads and sealing surfaces clean, as you sggest, and I am fussy about that. Its one reason why I decant with pipettes, so as not to get paint all over these surfaces.
I know that wine corks are not the same as paint bottle seals, and it wasn't intended to be taken literally (I have noticed that modelers interpret things quite literally, so I will be a little more careful). The anlaogy was used as one that illustrates the point and "sticks" well in the mind.
Thanks for your comments though. I wont use the latex caulk and will stick to good old petroleum jelly.