I wish I had a magic formula for you. I had bottles that were compromised that I revived, and some that would not. I can’t remember doing anything one way or another then just adding water and stirring for a long time.
Pollyscale and Polly S there are two different paints but from the same brand, RPM, the parent company of Floquill if I recall correctly.
Polly S was latex, I still have some that actually works.
Pollyscale was an actual acrylic paint. I still have bottles of it that work. In my opinion, Pollyscale was the best I’ve ever used. Years ago on the original site I did a comparison between Pollyscale, Tamiya and Model Masters, demonstrating their coverage, and resistance to masking tape and scratching with my fingernail. Pollyscale was the best, MM was the worst.
I’ll never forgive Testors/Model Master for killing off the superior Floquil and Pollyscale for MM.
Hee hee, I have some of my 1980s art school acrylics, gouches and oils that were still good last time I used them. That’s been over 4 years ago.
I also have some of the old c.1971 Pactra enamels (in the glass and eventually plastic bottles that were molded with paint drops on each side) that may still be good. Last time I used one of those was about 10 years ago. I’m holding on to them for some special nostalgia build.
About 25 years ago I bought a big set of Pactra 1 oz bottles of acrylic. All of those were still working without flaw last time I used them a little over 3 years ago.
It was May of 2023 that we moved. I tried to keep my paints indoors but some boxes of them were left out of the garage. And I also found a couple boxes that were in an air conditioned storage locker. I dread opening them to see if they’re still good.
This actually begs the question of whether using old paints, or less-old paints, have stood the test of time on the models themselves. Inevitably some paints will degrade over say 15 or 20+ years (most vulnerable are the brightest such as red), but I haven’t heard anyone report as such.
I’ve always used my el cheapo artists’ acrylics for camo schemes etc., on some of my oldest vehicles (pre-1999) I’ve recently looked at them and wondered (a) are the pigments degrading? Or (b) jeez you didn’t paint that very well in the first place. Given that I also used them for actual paintings, and I haven’t detected any pigments in retreat on those, I guess answer (b) is the truth.