Last coat of Satin Polyurethane

[Stephan Ramirez]

Hello, I've been finishing two beech butcherblock tabletops for a desk I'm making. I have applied 4 coats of gloss oil-based poly to the bottom with 1 coat of satin oil-based poly as the final coat. The sheen of the satin is very consistent across the whole piece, but there are plenty of dust-nibs and imperfections (no brush marks though). In order to get rid of the imperfections I went over the whole thing with some 0000 steel wool, but it didnt really knock down the imperfections very much and applying enough pressure to get the nibs out with the wool causes spots that are obviously very different in sheen than the rest of the piece. I've read that I should wet sand with 400, 600, 800, and so on until I reach the sheen I want (satin) using soapy water as lubricant. Finally I read to use 0000 steel wool to apply a paste wax or wool lube (not really sure what this does). Should I try to take the satin coat off before rubbing it? Does the process I put for rubbing seem correct? Also, is it difficult to achieve a uniform sheen by hand like with the satin poly or should I just accept the imperfections and move on?

One final question, one of my tables has developed a concave warp, I'm guessing from only finishing one side so far and the unfinished side drying out from my exhaust fan pulling air over it. Should I just finish the unfinished side and wait a few weeks and hope the warp goes away or should I try to fix it some other way before I apply poly?

[John TenEyck]

Either of the methods you described to rub out the finish should work. I often use 0000 steel wool and paste wax to rub out a table top from gloss to satin. The paste wax (or wool lube) lubricate the steel wool. You could use soapy water, too, if you use synthetic abrasive pads or brass wool. The lubricant carries away the particles the abrasive cuts off as you rub and prevents them from damaging the finish. The key in any case is to use a block of wood, etc. on top of the steel wool, abrasive pad, etc. to keep the surface flat. That might be the source of your difficulties if you didn't use one.

I find it better to apply coats of finish alternately to a table top to prevent the warping problem you described. Where you are now I would go ahead and finish the other side so the same number of coats is on both sides then just wait. It should flatten out again once the moisture inside equilibrates. Keep the top elevated so air can circulate freely both top and bottom.

John

[Stephan Ramirez]

Thank you for the help. Since I still have the top to do, the side that matters the most, should I finish with a satin coat if I'm going to rub it down, or just end with gloss?
My process I think will finish the top and give that about a week or 2 to dry, then begin rubbing out the finish for the bottom to practice, then the top, maybe giving some time for the warp to go away.
For the actual rubbing out, would it make sense to wet sand with 400, 600, etc. using soapy water and then do the steel wool with wool lube, or should I just do one or the other? About how high of sandpaper grit should I go to get a satin, if that's the advisable method?
Using the steel wool with a decent amount of pressure in my hand seemed to make the satin coat glossy, but I am going to use my sanding block for the wool in the future. Again, thank you for the advice.

Edit: I guess the sandpaper portion would be considered leveling while the steel wool would be the rubbing? So maybe go up to 1200 with sand paper and then steel wool with lube?

[John TenEyck]

I only use gloss if I intend to rub out the finish. I use satin, or whatever sheen other than gloss, when I have no intention of rubbing it out. As you found out, when you rub satin it's easy to get a higher sheen. Seems counter intuitive, but it's not. What you are doing is rounding over the flatters, the particles added to finishes to lower the sheen, and that increases the sheen.

Rather than me confusing the issue, I suggest you read Jeff Jewitt's excellent article on rubbing out a finish: https://homesteadfinishingproducts.c...-out-finishes/

John

[Bennett Ostroff]

The rubbing out thing is such a pain and I never like the look. If it were me, I would sand smooth, do one more last coat of satin to get an even sheen, wait a week, then go over very lightly with like 1500 grit sandpaper and that should smooth it out adequately.

I’ve also done a final spray coat (rattle can) of Minwax satin oil based poly on some projects. A couple very light coats. Leaves a really nice sheen and dries very quickly with minimal dust nibs, and easy to smooth out. I usually do it a few hours after my final coat of wipe on. Mask and ventilation is a must.