FAQ

Distilled solvent will reach such a level of purity that many hospital pathology laboratories distilled their spent solvent and re-used it for the original purpose.
If the distilled solvent is a mixed product containing more than 1 product, it is best to use it for “washing”. If it contains only 1 product such as “acetone, MEK, toluene, etc.” you can run a test and then determine if it is suitable for thinning.
Before doing so check your local regulations and find out if it is allowed.