Polyurethane over red oak

[Prashun Patel]

Hi. I'm Shawn. I'm a long time lurker, first time poster. Searched for answers to this, but could not find:

I'm finishing a red oak bench that I built from 1x stock and oak plywood. Stained (Minwax oil) and polyurethaned (gloss).

Problem: I have some 'pits' in the oak grain that refuse to fill up.

I sanded to 150gt unfinished, then stained, then poly'd. I sanded 320 and 400gt wet in between poly coats (thinned to 75-90% with spirits). Used an excellent brush. No bubbles or drips.

Now, I'm trying to rub out the finish and I see pits all over the place on the 1x stock (about as long but 1/2 thin as rye bread seeds). The plywood doesn't have the same prob as badly.

I tried aggressively sanding down the finish with 320gt, but I went thru to the wood.

Was I supposed to fill the grain before or after staining? If I do it b4 staining, won't I impede the stain's ability to penetrate? If I do it after staining, won't I risk sanding off the stain when I sand down the filler?

Or is this just par for the course on red oak?

BTW, my oak's from HD. Does that have anything to do with it???

Thanks in advance,
Shawn

[Steve Schoene]

While wood from Home Depot is often sub-standard I doubt that has anything to do with your situation.

Red oak has large, deep pores. (They virtually run the entire length of the board). They are a challenge to fill. If that is your goal, it is easiest to use a pore filler. One sequence is to 1) stain or dye, 2) lightly seal, 3)apply pore filler, wipe off excess before it dries fully This way you don't have to worry about not getting the pore filler to accept stain. There should be very little pore filler on the surface to sand. With oak, especially red oak, two applications of pore filler may be needed, 4) let pore filler cure, 5) apply varnish top coats.

Filling the pores with the top coat can work, but as you saw, sometimes it is hard to avoid sanding into the wood. With oak, it may well take a double digit number of coats to fill the pores fully. I hope when you mentioned how you tinned the varnish it meant that you added from between 10% to 25% thinner, if it was the otherway it would take for ever to fill pores. Use as little thinner as possible, just enough so it will flow out and let bubbles pop. (There will only be the equivalent of a few coats left on the surface. This is the hard way.) You should use a clear coat that sands better than polyurethane varnish. One possibly is shellac, which can then be overcoated with a varnish if you need extra protection. Use dewaxed shellac if you persist in top coating with polyurethane varnish or use a water borne top coat. Traditional resin varnishes will adhere to shellac with without the wax removed.

A little careful application of your stain--possibly with some touch up with a small brush, may give an acceptable fix to the sand through. It's tricky, and hard to get perfect, but if it's in an inconspicuous location you will be OK.

[Prashun Patel]

Thanks, so much, Steve.

LOL: I was thinning properly (75-90% pu + 10-25% spirits).

I'll use a pore filler next time.

Newbie questions here: Why seal between stain and pore fill coat? Also, since the pore filler is a different color from the stain, wouldn't I have to stain again after the fill coat? So wouldn't the sequence be like this? :

stain
seal
fill pores
stain
seal
top coats

[Joe Chritz]

You will be unlikely to get a smooth top with oak in which you don't see the pores filled. It is the nature of the beast so to speak. Some fillers can be stained and others are colored when mixed up.

You seal with shellac before filling to keep the filler from staining the wood and to help it scrape off better.

I haven't even found a filler I really like for tops, although I don't have much experience using them. If I want a smooth top I opt for maple or cherry.

Joe

[Steve Schoene]

It's a challenge, but I wouldn't say its an impossibility. It almost certainly calls for two applications of oil-based pore filler, spaced at least a week apart so that shrinking of the first has been nearly completed before the second coat of pore filler. I like to tint Behlen's Pore O Pac with artists oils. The tint can make the pores lighter or darker than the surface in between, or even be a contrasting color entirely, such as purple filler on a yellow dyed surface.

[Prashun Patel]

Thanks all for the help!!!

[Noble Bowes]

at some point u needed sanding sealer