Saltpeter, or potassium nitrate, is usually available in garden or home improvement stores and from pharmaceutical and food chemical companies. The place where a buyer gets this product depends primarily on the intended use.
Saltpeter that is used as fertilizer, stump remover or oxidizer for fireworks and rockets may be purchased from garden supply or home improvement stores. One brand of potassium nitrate to look for is Spectracide. Saltpeter that is used for curing meat such as ham and bacon or as medication for asthma and sensitive teeth must be food-grade and can be purchased from pharmaceutical or food companies such as Penn Herb Co. Ltd.