I've got some old acrylic paint bottles that look really separated - there's this watery stuff on top and the pigment settled at the bottom. I've tried shaking them but it doesn't seem to mix back together properly. Is there a way to fix this or should I just toss them?
Separation in old acrylics is pretty normal - that watery stuff is just binder that's evaporated slightly or settled out. Try adding a few drops of water or a tiny bit of acrylic medium, then stir slowly and thoroughly with a brush or stick rather than shaking, which can trap air bubbles. If it still won't come together after stirring for a minute or two, you might need to add a thickening agent like an acrylic gel medium to help bind everything back together. If the paint's been sitting for years and still won't mix properly even after that, it's probably past saving and safer to replace it.
Old acrylics that separate like that are usually still salvageable, but you gotta be patient with mixing - quick shaking won't cut it, you need to actually stir it slowly with a stick or palette knife for a minute or two to get the pigment back into suspension. I had some paint sitting in a garage for way too long and the same thing happened; once I stirred it properly and added maybe a drop of water, it came back to life and worked fine.
If it still won't mix after that, or if it smells off or looks moldy, then yeah toss it - but most of the time it's just the binder settling and you can bring it back.
The best move is to grab a wooden stick or old palette knife and actually stir the paint - not shake it. Get down to the bottom of the bottle where all that pigment's sitting and work it slowly until the consistency looks even throughout. This takes patience, maybe a couple minutes of real stirring, but it usually works. If the paint's too thick after stirring, add a drop or two of water and mix again. You can also use acrylic medium instead of water if you want to preserve the paint's binding properties better.
One thing people don't always mention: don't assume the paint's ruined just because it separated badly. Even if it looks like concrete at the bottom, there's usually nothing actually wrong with it - it just needs proper mixing. The real trap is adding too much water at once. Start with tiny amounts and stir between each drop, because once acrylic gets too diluted it loses its grip and won't adhere properly to your surface. If after stirring and adding a little liquid the paint still feels off, that's when you can consider tossing it, but most old separated acrylics come back to life pretty easily.
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