This is prepared by adding a small percentage of formaldehyde to a warm solution of gelatin, which is then whisked into a foam and freeze-dried. The porous product is cut into pieces of suitable size and sterilized by dry heat at 140°C. When pressed tightly onto a bleeding area, blood is taken up and clotting is encouraged by the large rough surface, which causes platelet disintegration. The sponge also acts as a plug by sticking to the underlying tissues and mechanically supporting the clot over the oozing vessels.

The sponge is nonantigenic and tissue reactions have been mild. The standards include a test for digestibility in acid pepsin solution. Since some microorganisms liquefy gelatin, it should not be used in septic wounds, nor is it suitable for arresting hemorrhage from large wounds. It is marketed as white or near-white, rectangular, very porous pieces that are extremely light and have a papery feel.