Can paint spoil

Answer 1

Most paints do, either by drying or by rotting. Egg tempera (real egg tempera) can be used for a few days and then it starts to smell bad, caseine paint too, unless lots of preservatives were added. Factory egg tempera and caseine paints contain preservatives to prevent it from rotting.

Oil paint should be kept away from oxygen, because that 's what makes it dry. (if partly dried, it won't make a good paint film anymore). For acrylic paint, it's more or less the same.

Answer 2

yes. after a period of time, it gets to the point where it is no longer efficiently usable. You can tell because it will have a strange texture and, if you try to paint something, it wont go on the wall right. (though, i cant remember if it gets thinner and watery, or thicker with a layer of liquid on top.)

Answer 3

Some paint can expire. I don't think that applies to modern enamel paint as long as it remains closed. In my experience milk paint will expire in a few years, even when not opened. This applies to a lesser degree in latex paints.

Answer 4

depends on type of paint and room humidity

Answer 5

Eventually, they will evaporate and sour even in a sealed container.