Dry cross-linked gelatin compositions are prepared that rapidly re-hydrate to produce gelatin hydrogels suitable as hemostatic sealants. Gelatin is cross-linked in the presence of certain re-hydration aids, such as polyethylene glycol, polyvinylprovidone, and dextran, in order to produce a dry cross-linked gelatin powder. The use of the re-hydration aids has been found to substantially increase the re-hydration rate in the presence of an aqueous re-hydration medium, typically thrombin-containing saline.