I think that the water problem is from limestone minerals in the well water, which will leave a slight residue of calcium on the barrels when they dry after boiling. This can leave lines of calcine which will inhibit the next application of the acidic bluing solution, causing variations in the next coat. Put some of your water in a polished stainless pan, and boil it off. The chalky residue is calcium carbonate.

hippie redneck geezer