I know that the answer to the question "Which animal product can be softened with water?" is in "The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on rawhide, paper, or cloth. Within certain limits, the greater the water content, the greater its softening effect.". Can you tell me what it is?
The answer to this question is:
rawhide