Any solution with a pH of 3.0 or lower will dissolve beer stone. Beer stone is calcium oxalate (the same compound as a kidney stone). The pH of double-strength Star San will get one there, but there are cheaper ways to dissolve beer stone. The pH of straight white vinegar is 2.5. A gallon is less than $3.00. Like, Star San, it can be sprayed onto a surface. The downside is the aroma.