You can also sand to take care of drips etc but proper application technique should avoid those.
Scuff sand floor between coats.
The finish on the floor in the photo at right is intact but a recoat won t help much.
4 x research source if you are scuffing bare wood or another surface in preparation for priming painting and or staining you will need something between p120 and p150.
Even easier for this step though would probably be a pole sander like the kind for drywall seams.
And now you ll have to sand the entire floor with 220 grit sand paper and clean all the dust up.
While it is physically possible to recoat floors like these and even have the new coat bond well the damage will still be visible through the fresh coat of finish effectively preserved under plastic.
This is an area where prevention is better than cure definitely applies.
In most cases you will scuff sand a bare surface before applying anything and sand again between coats of paint or sealer.
The only type of bond that is possible between coats may be a mechanical bond created by sanding scratches.
Use a very fine grit abrasive sanding with the grain of the wood.
Be careful with floors that look like they can be recoated.
It s true in my experience that most first coats make you look like a monkey s.
But you re correct sanding between coats of poly isn t stripping an old floor it s just scuffing up the previous coat of poly in preparation for the next one.
Sand the dried and cured first coat of polyurethane no sooner than 24 hours after applying it.
Charles recommends you watch the 3 trace co.
Here is what you should look for.
Sucks to be you.
The reasons you may need to sand between coats are to de nib that is to take off dust specs and knock the tops off any bubbles in the finish.
Use a fine grit paper and run it over the whole floor you don t need much pressure.
Just kidding but i truly do hate sanding when i don t have to.