where can I purchase alum from
1 Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit and vegetable crispness. 2  Alum is used as the acidic component of some commercial baking powders. 3  Alum was used by bakers in England during the 1800s to make bread whiter.n Alum Block sold as an astringent in pharmacies in India. 1  Alum in block form (usually potassium alum) can be used as a blood coagulant. 2  Styptic pencils containing aluminium sulfate or potassium aluminium sulfate are used as astringents to prevent bleeding from small shaving cuts.