Expert: Greg Scholl - 11/25/2011

Question
QUESTION: I am refinishing an oak dining room table that is about 35 yrs old.  I stripped all the old finish and stain off, then put two coats of stain on.  I am now applying Minwax oil based polyurethane as the final finish.  Problem is, I am on the 4th coat, and I am still getting imperfections that look like the poly is not going into some of the grain lines.  They are very small in size and not very noticeable.  The more coats I put on, the fewer of the flaws, but I am getting a little tired of so many coats.  I have been waiting 4-6 hours between each coat of poly.
Thanks for your help.

ANSWER: Hey Don, 4-6hrs. is not enough time between coats, you should wait at least overnight (12hrs.+), and touch the finish with a fingernail lightly to see if it's hard enough.The act of applying another coat too soon will soften the previous coat, and even remove some of it....were you careful to wipe OFF the stain coats you applied? Many people leave the stain too thick when trying to get a dark, rich color, especially on a hard wood like Oak....and that's a no-no, that can cause several issues....if one wants a darker color, it's best to employ a different stain like a dye or Gel or combination of the two on a hard wood.What you're describing sounds like the open pores of the Oak are showing, and that's normal for Oak...if you want a glass smooth, pore filled finish,(not common on Oak furniture), then you would have had to employ a pore filler in your finish schedule....post back with a pic if possible- regards- Greg

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QUESTION: Well since I have already applied 4 coats I can't stop now.  I will wait the 12 hrs between coats if I decide to apply more.  You are right that I think it is the open pores of the wood grain, as they are in line with the grain in the more coarse areas.  We did not use a pore filler (never heard of it# in the prep, and we did remove the stain prior to applying the finish.  In fact we had to do a fair amount of sanding and reapplying of the stain to get the color right #hard to get it even on oak).  Do you think we will be able to get the pores filled if we keep applying more thin coats of poly or can we use the pore filler now and finish over it?

ANSWER: Eventually the grain will be filled, but by that time you'll have an 1/8" of poly on it. The pore filler must be used before the finish, so you cant add it now. Remember, with poly, which is a modified varnish, each successive coat is it's own layer, so thin coats should be shied away from...a full, wet coat for each application. One way to fill the pores now would be to wet sand the dry finish (after 24hrs or more dry time) with some 400 wet/dry sandpaper and some water( take a Chinese soup sized container and fill it with warm water and add about 4-5 drops of a liquid dishwashing detergent as a lubricant) in long overlapping strokes drying as you go, until you've knocked back the finish, but be VERY careful NOT to sand through....as you'll ruin the stain coat.wipe it down with water and hand dry it.Then reapply another coat of poly...and so on....but open pores are the norm on Oak furniture for the most part, as it's difficult to fill them up fully.Are you spraying or brushing your top coats?

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QUESTION: We are brushing the poly on.  I have been dry sanding with 400 grit paper then wiping down with a tack cloth between all coats.

Answer
I bet your sandpaper is clogging fast, especially after only 4-6 hours dry time...you say 'thin' coats....does this mean you're thinning the poly? You should apply it full strength and only sand if it's rough to the touch (unless you're wet sanding to cut the finish back and reduce the open pores, of course)...