Tanning is the process of converting putrescible skin into non-putrescible leather, usually with tannin, an acidic chemical compound that prevents decomposition and often imparts color. Tanning leather involves a process which permanently alters the protein structure of skin so that it can not ever return to rawhide. Making rawhide doesn't require the use of tannin and is made simply by removing the flesh and then the hair by way of soaking in an aqueous solution (often called liming when usin… (More on Tanning)