The hardwood ashes will not tan the deer hide, we use the hardwood ash to remove the hair from the hide before tanning, basically to make raw hide, the ashes in rain water makes a caustic solution (lye or caustic soda) the caustic soda water takes the oils from the hide making soap, the swelling hide can then be DE-haired with simple scraping (to make raw hide before tanning the leather... (if the hide is left too long in the caustic solution and warmer temperature where the reactions are intinsified, the hide itself can dissolve in the caustic solution) a hide left too long in the caustic bath can become holy raw hides. :lol:
Gloves are a good idea.
Glasses or a face shield are a must, caustic soda in your eyes is one way to easily go blind, as your eye ball dissolves. Even washing your eyes with water is not much help if you get caustic soda in them, it takes tons of water to neutralize a drop of caustic, and who in their right mind would want to pour acid in your eyes to neutralize the caustic in their eyes while the caustic is dissolving their eyeballs?
I never personally wear gloves when De-hairing or tanning hides, but my hands have always been so callused, the caustic solution just made my hands cleaner and a bit more softer by removing the harder callused skin.
The hydroxide or caustic solution will make soap from the oils in your skin, if left long enough in solution it can dissolve all of the meat from your bones.
Back in the olden days when men sailed in ships on long voyages, when someone died on the ship they had two choices of dealing with the body, to dump it overboard burial at sea, or sometimes they may have wished to store the body to be buried on land, which may take months to reach land. without refrigeration or a way to safely store the body (and not creating disease on ship) they would pack the body in wooden barrels of caustic soda (fresh water and wood ash), the caustic solution would eat all the flesh from the bones, they could then dump this soap overboard, and dry the bleached bones and haul them with them until they reached land for burial.