Baking Powder Gluten & Aluminium Free 12.5KG, Product Of Australia
Baking powder combines acid and alkaline substances that act together when in contact with moisture to create gas bubbles, which expand during baking to give a fine, delicate-textured result. It is sold in airtight packaging and great care should be taken to keep it dry, as any hint of moisture will set the chemicals working. When adding milk or water to a baking powder and flour mixture, you need to work quickly so that the resulting carbon dioxide has little chance to work.
*this description comes from "The Kitchen Handbook" Page 105