I have another query. I had a sapele wood staircase installed in my house. Builders (with little experience of wood I think) varnished it, possibly without cleaning it first, and there were ugly whitish smudges. They sanded the smudges off partially but the wood retains a patchy 'unwashed' appearance. Before varnishing it again (and possibly aggravating the problem) I thought I'd ask for advice. Peter