I am putting this spalted beech top on an old sewing machine base. My wife will use her sewing machine on it so I am wondering about the best finish. It can’t be anything that might leave residue on material and needs to be tough enough for light bashes like dropping scissors etc. I think polyurethane varnish would do this, but it often yellows timber. I have thought about Osmo but have never used it. Any other options or advice would be appreciated please?