Check your spice rack! Baking powder often contains calcium carbonate. Look for “calcium phosphate” or “calcium hydrogen phosphate” in the ingredients list, too; these are related compounds. While not pure calcium carbonate, they’re good sources.
Eggshells are another excellent source. After boiling eggs, carefully wash and dry the shells. Grind them into a fine powder using a mortar and pestle or a spice grinder for easy use. Remember to thoroughly clean and dry the shells before grinding.
Antacids like Tums or Rolaids primarily consist of calcium carbonate. Check the label to confirm the active ingredient. Use these with caution, though, as they are intended for medicinal purposes.
Milk and other dairy products contain calcium, but not in the carbonate form. You’d need to process them further to isolate calcium carbonate, which is generally not a practical kitchen task.
