Q: I would like to change/darken the stained color of the stairs. Which product could I use over polyurethane without sanding or stripping existing coats? Would a stained polyurethane product work over the clear polyurethane as sort of a top-coat?
A: There are tinted varnish products. But this is applying finish and colour to the top of what is on your steps. There is no bond between the wood and finish. To me, this is like continually covering one floor covering with another. I have been in houses like this. There are multiple layers of flooring:tile, more tile, plywood, more vinyl, more plywood, hardwood, more plywood…..I don’t believe in quick fixes.