After cleaning brushes, I pour the thinner in a gallon bottle that I
mark "Old Paint Thinner". The paint solids go out of solution and
solidify in one mass, leaving clear thinner that can be used again for
cleaning. I would not use this for thinning paint though. It does take a while
for the action to take place. When the mass of solidified paint solids
gets close to filling the bottle, you can take it to a hazedous waste
disposal facility.
