Will my finishing solvents go bad over time?
Do solvents, such as denatured alcohol, mineral spirits, acetone, or lacquer thinner, ever go bad or have a "best-if-used-by" shelf-life?
—Mark Thomas, Galveston, Texas
Mark, we posed your question to Bob Flexner, a leading authority on all things finishing, and he says that solvents—if stored in their closed containers—never lose their ability to thin or clean up finishes. However, if left open, solvents do evaporate.