Do I use steel wool to buff before 4th coat?

Q: I just re finished my friends floor, white oak random, width 3 5 7. It was a pain to sand. We put a lite stain on and 3 coats of sealer, sanding in between coats, and 1 semi gloss. Now my friend wants another coat of semi gloss. Do I use steel wool this this time, before I put the last coat on?

A: I would need to know first what type of sealer was used. I use Poloplaz Fast Dry sanding sealer which is actually a fast dry polyurethane but is designed to penetrate well into the surface of the floor. It is a tough sealer but easy to work with. Generally 1 coat is all that is needed. You might use 2 as a less costly way to gain finish build. I then follow with Poloplaz Primero, generally gloss first and then satin or sheen of choice. These are all solvent based coatings, not water borne.

Never use steel wool with water borne.

Assuming it isn’t water borne, then yes each coat should be buffed or scratched to gain a mechanical bond between coats. You can use steel wool, though I haven’t heard of anyone using that in years with all the ‘revolutionary’ buffing pads now available to perform the task without leaving swirls or at least limiting them. I would start with the finest abrasive to see if it buffs sufficiently. That would be a 3M maroon pad with or without 180 grit sanding strips attached. If the finish is too hard to buff then I would move to a 220 grit screen. Still not course enough? 180 grit. Norton has also recently come out with a new pad (haven’t tried one yet) which comes in various levels of coarseness. Not suppose to leave visible scratch marks.

I don’t generally recommend more than 3 coats initially because it could slow down the cure of the finish. Always follow the spread rate, generally 500 sq. feet per gallon. Thicker coats are not better.