Tanning's the process of making leather, which doesn't easily decompose, from the skins of animals, which do. Often this uses tannin, an acidic chemical compound. Coloring may occur during tanning. Tanning leather involves a process which permanently alters the protein structure of skin so that it can't ever return to rawhide. Making rawhide doesn't require the use of tannin and's made simply by removing the flesh and then the hair by way of soaking in an aqueous solution (often called liming w… (More on Tanning)