What, exactly, is pickling salt? If a recipe calls for it, may I use instead a coarse sea salt to which no anti-caking agents or other substances have been added? And if so, should it be used at a ration of 1 to 1? Thank you. ;o)
measure by weight instead of volume.
Kosher salt is a better substitute. The reason to use canning/pickling salt is to keep the color bright and green. Using any other salts can make your brine cloudy or darken your pickled vegetables. (From a long time canner!)
As much as I tinker with recipes (even when baking), I follow recipes for preserving/canning to the letter. To further insure that my name isn't in the headlines for killing my family with botulism, I only use recipes from trusted sources, such as university home economists, Better Homes and Gardens and the Ball/Kerr glass companies.
As Christina advises, the only substitute for pickling/canning salt is Kosher salt. Not only do you want your finished product to look good, you also want a properly-made brine to kill off any nasty spores before they kill you.
1/2 cup pickling salt = 1/2 cup plus 2 Tablespoons Kosher salt.