Leather Gaskets, Anyone

Interesting question. Leather's cool for a lot of things. Gasket paper also absorbs liquids and swells, and it has the advantage of consistent thickness. Remember, the case and cylinder gaskets are shims designed to give proper spacing to your metal parts and is a lot easier to work with, not to mention availability. Cork is also a great sealing material, but where you need something strong, regulation gasket material is the way to go. Leather or cork would work fine on side covers and non torqued areas. I've used leather for cups in pumps and seals around non pressurized shafts, so there is a place to use leather for sealing.