So-called hard waters should not be used in making a brine. The presence
of large quantities of calcium salts and possibly other salts found
in many natural waters may prevent the proper acid formation, thus
interfering with normal curing. The addition of a small quantity of
vinegar serves to overcome alkalinity when hard water must be used. If
present in any appreciable quantity, iron is objectionable, causing a
blackening of the pickles under some conditions.