How do you use alum water for pickling?

According to the USDA, alum may still safely be used to firm fermented cucumbers, but it does not improve the firmness of quick-process pickles. If you use good-quality ingredients and follow current canning methods, alum is not needed. If you do use alum, do not use more than 1/4 teaspoon per quart of pickling liquid. Excess will cause bitterness. For up-to-date canning recipes, contact your local county Extension agency.