Superabsorbent Polymers (SAP) are polymers that can absorb and retain extremely large volumes of liquid. Amazingly, water absorbing polymers (hydrogels) can absorb and retain up to 500 times their own weight in water. Their absorbency is determined by the type and ratio of cross-linking agents used to make the gel. Low density cross-linked SAPs have a larger absorbent capacity, while the higher cross-linked SAPs have lower absorbent capacity but form firmer gels.