I have just polyurethaned my hallway. The first two coats were allowed to dry for 24 hours each. Tonight there is this layer of oil on top of the urethane. It is not tacky, not still wet; it's just oily. I tried wiping it up, and more just keeps coming up. Is this a normal part of some sort of curing process? Did I do something wrong? I used Minwax's poly. Anyone who can help, I'd really appreciate it.