Oakum's a preparation of tarred fibre used in shipbuilding, for caulking or packing the joints of timbers in wooden vessels and the deck planking of iron and steel ships, as well as cast iron plumbing applications. Oakum was at one time made from old tarry ropes and cordage of vessels, and its picking and preparation has been a common penal occupation in prisons and workhouses. In modern times it's made from virgin hemp fibers. White oakum's made from untarred materials. The fibrous material us… (More on Oakum)