Paint Can has green water?

Question

I have a paint can that is dry, but other than that, there is a green water like on top of the paint, I just was curious onto what is it? The paint has condensed into a clay like, which, cannot be used as paint no more.

Answer 1

The paint is made up of water (if it is water base) and oil (if it is petroleum base) and pigment. As paint ages, the pigment and the base start to separate mostly because they are two different masses. (like mixing oil and water... if you leave the combination sit long enough, you have a band of water and a band of oil.) If you add temperature fluctuations or a loose seal on the can, the water will start to evaporate. As temperatures drop the water will condense inside the can, which will cause the pigment to become more 'solid'. (The green is caused by some residual pigment and water mixing... unless the paint is some color that does not have green in it. If it is not green pigment, it is mold.)