bought a butcher block with almost perfect surface at a garage sale five-six years ago for seventy-five bucks. thought i got an awesome deal, til i got it home and realized it had been finished with polyurethane or something. after about 20 hours of sanding, i have a stain seeping up to the top which is obvious underneath. seems to be some type of oil. the top is about two and three-quarters thick. is there anyway safe to get this out and still be able to use the top for food prep? i purchased a butcher block conditioning compound before i found the stain, don't know if this will cure the problem.