‘Hydrogel’ is the common generic name for the polyacrylamide class of polymers. These polymers typically have low density when dry, but have the capacity to absorb enormous quantities of water to form a stable gel which holds the water for an extended period. This completely non-toxic powder absorbs up to 500 times its own weight in water and is the ‘secret’ ingredient used in applications ranging from babies nappies to perpetual growing plants. Includes 500g of powder.