Borax is used in some taxidermy work to preserve small skins for mounting because they do not need to be flexible in a mount. It stays there and never moves so it does not need to do anything. This is curing a hide and it remains flexble until it dries on the form. Leather, be it grained or grain on, if it is going to have to move, needs to be dressed, or tanned in order to keep it pliable. Although borax is a great preservative for small mounts lacks the tanning qualities of any of the commercial "salts" and acids that preserve the hide and oils that coat the fibers to keep them from bonding together and stiffining the hide. If all you want is a skin to tack up on the wall or lay in front of a fire place for a rustic look, dry preserving will work for a while. But it wont be pliable and will shrink and curl over time making it a hair on "rawhide" If its going to be tanned into something of use, ie leather or a robe, it needs to be pickled, tanned, oiled, and broken down. Using salt to draw the moisture out of the hide and retard the bacterial growth to keep the hide from rotting has been accomplished for thousands of years. As I wrote before, I deal with hundreds of hides every year from ringtail cats to horses, buffalo, elk, and many others and the best way I have had to keep them ok until I can tan them is flesh them down completely, all flesh and fat using salt to help the blade catch, then resalt, dry and store. Borax and instant preserve are good for what they were intended for, but the only way to have a nice robe, or rug is to tan the hide.