When I remodeled the old house, I redid the hardwood floors. There were
stains embedded into the wood from the carpet pads. They were usually
isolated is spots. One room i had to melt off the old foam. After light
sanding with the Varathane sanding machine, the spots were still
visible in to some extent. After experimenting, I found a way to get
rid of the spots. i used Oxi-Clean. 2 or 3 spoonfulls into about a half
to one gallon mixture. After applying one coat, wait and apply more
coats as necessary, and the fluid may have to be rejunivated. You
cannot see the final results until after it dries. It reacts
differently with different woods. On the main floor I did the prep.
After applying 3 coats of polyurethane, the floor looked terrible.
Actually turned blackish in spots. I was disappointed or at least for a
day or so. the wood turned beautifull after a day or two to three days,
and it continued to lighten up. Other floors didn't turn black at
first like the main floor, so I think the preparation and wood types
can vary the process. I just wanted to possibly recommend trying
oxi-clean on unfinished outside wood, but it has to be soaked on, and
not pressure washed, or at least thats how i view it. The drying
process is essential to the cleaning process. Several wet-dry
treatments will provide the most action.