Thanks, OTH, you make a good point. I wouldn't get the concentrated stuff near the steel (or me) anyway, and it serves as a good warning to be aware when leaving any solvents in the bore for long periods of time. My electrolyte solution is 50/50 household ammonia and white vinegar, and I have left the cleaner running overnight on severely fouled milsurps without any problems, but the vinegar (acetic acid) in it serves as a buffer to balance acid/alkali. I assume the pH is around 7 (neutral) but I have not tested it. Now you've gone and gotten me curious. I should send a sample in with my daughter to her chemistry class to find out.