Can I use #0000 steel wool for final polish of water-based polyurethane?

Question

I'm finishing my first woodworking project — a tabletop that I hope to mount on a sit/stand desk mechanism.

I've stained and applied 4 coats of Varthane water-based polyurethane in matte finish. I applied each successive coat after lightly sanding between coats with 400 grit sandpaper and achieved a finish I'm pretty content with. I'm now on the final steps and have a couple questions...

I'd like to apply a final protective barrier and achieve an ultra-smooth feel to the hand. I've read about using #0000 steel wool and polishing with automotive wax or carnauba wax. However, I'm a bit conflicted with some people advising against steel wool on a water-based varnish. I've also read in other forums that steel wool is not a problem on water-based varnishes as long as it is used on the final coat and it has been thoroughly dried. Can I use #0000 steel wool as a final polishing step? If not, what are my alternatives? I've read mixed reviews on synthetic wools, do you recommend them? What course grit?

Any recommendations are welcome. Thank you so much in advance!

Answer 1

Short answer, yes.

I should caution you that 0000 steel wool won't polish it per se, rather it will have the opposite effect of scratching the surface (they're very very fine scratches, but scratches nonetheless). So even lubricated by wax you'll be left with a somewhat satin or semi-gloss finish. If you want something glossier than this you should go another route.

Finishing sources are conflicted about whether you should use steel wool for the final dressing of a dried clear finish*. Bob Flexner, one particularly trustworthy source, recommends against using steel wool for denibbing and final flatting because it (along with other conformable abrasives) have more of a rounding-off effect than a cutting or shearing action.

So fine abrasive paper is to be preferred if a very flat surface is desired. You can modify this sanded surface subsequently by using steel wool, with or without wax, if it gives the look you like.

There is much info in previous Q&As here that touch on or directly answer some of your other queries (e.g. the use or not of wax, variability of drying and curing times, grit progressions should you choose to sand and polish).

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*Do remember that doing nothing at all to the finish (other than any denibbing that may be necessary) is an option. This is actually the ideal situation to aim for. In case you haven't read this tip before the rough side of brown paper can be used for this denibbing operation, it's just abrasive enough and shouldn't scuff any decent finish after it has had a decent interval to harden up.