Has anyone ever read the MSDSs on USA watch cleaners and rinses? http://lrultrasonics.com/msds/111%20Ultrasonic%20Watch%20Cleaning%20Solution.pdf http://lrultrasonics.com/msds/3%20Watch%20Rinsing%20Solution.pdf You are already using naptha. It ain't the naptha that will kill ya, it is that cigarette ya smoke in the shop. (Or that frayed wire on your cleaning machine). FWIW, I keep all unused cleaner, rinse and waste in the garage (detached). Because the stuff is naptha based, you can usually take it to the paint table at the landfill. In some states you can seal it in a paint can after solidifying it with kitty litter.