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Calcium and aluminum salts improve pickle firmness by combining the pectin to make the cucumber more resistant to softening. Alum (aluminum potassium sulfate) has been shown to cause a slight increase in pH and a significant increase in firmness when used at levels up to ¼ teaspoon per pint. Addition of greater than ¼ teaspoon alum per pint decreased the firmness (research done by Marilyn Swanson, Extension Food and Nutrition Specialist, University of Idaho). Alum is sold in the spice section of grocery stores. Too much alum will give pickles a bitter flavor and may cause digestive upset.

Pickling lime (calcium hydroxide) may be used in a lime-water solution for soaking fresh cucumbers 12-24 hours before pickling with vinegar, sugar, and spices. The lime-water solution must be drained after the soak and the cucumbers then washed at least three times in fresh water to ensure safe pickles. This washing is very important because lime is very alkaline and it is essential to remove the lime to be sure the pickle is safely acidified. Several recipes, which use a lime soak, are included in the USDA food preservation guide.

Lime used in pickling must be food-grade. Several food preservation companies now offer food-grade-pickling lime. Lime sold in lumberyards is industrial grade and may contain contaminants.

Water that contains calcium will help produce a firm pickle.