I am trying to refinish an old library card catalog (currently legless and used as a coffee table). It seems that originally, they must have gone without stain and used a sealer over natural wood. I have (in an inconspicuous place) sanded to bare wood, but it will not absorb stain. I have tried a chemical stripper, and denatured alcohol, still no go. I have tried oil based stain, water based stain, and gel stain. It simply refuses to take stain. Any suggestions?