Furniture, Wood and Cabinetry Finishing - Water Based Polyurethane Base Coat
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johnCT
03-20-07, 07:58 AM
Hi all. I plan on using a water-based poly to finish a new oak staircase. The oak will not be stained and planned on using the WB for the improved color qualities. My question is regarding the Minwax base coat product they offer which is supposed to seal the wood grain preventing a supposed tanin reaction that will discolor the finish. At $42 a gallon, is this step really necessary? Also, what's the best way to apply the poly? Thanks.
clockdaddy
03-20-07, 03:15 PM
johnCT,
Using water based poly is no big deal. There is no need to seal the wood because polyurethane (whether it's water or petrol based) is it's own sealer. The water based poly is somewhat thinner and you will need to apply a few more coats in order to achieve that "showroom" look.
Make sure the floor and steps are thoroughly sanded and clean. Using a 4 inch brush suitable for use with water based finishes, start applying the finish by brushing with the grain of the wood. There may be times when you HAVE to go across the grain. Simply take the tips of the brush and run them with the grain to take out lap marks. Allow the first coat to dry thoroughly but no longer than 24 to 48 hours. Using 220 grit garnet sandpaper and sanding with the grain, sand the entire area just enough to make it feel slick. The best finishes are made by applying thin, even coats of finish and sanding thoroughly between coats. Vacuum the surfaces clean using a shop vac and proceed with your next coat. You'll probably need (if it's new wood) 3 to 5 coats of finish.
Be patient, mix your finishes thoroughly, follow the application instructions on the container and in a few days you'll have a nice finished floor and sore knees!!
Best of luck,
CD
Using water based poly is no big deal. There is no need to seal the wood because polyurethane (whether it's water or petrol based) is it's own sealer. The water based poly is somewhat thinner and you will need to apply a few more coats in order to achieve that "showroom" look.
Make sure the floor and steps are thoroughly sanded and clean. Using a 4 inch brush suitable for use with water based finishes, start applying the finish by brushing with the grain of the wood. There may be times when you HAVE to go across the grain. Simply take the tips of the brush and run them with the grain to take out lap marks. Allow the first coat to dry thoroughly but no longer than 24 to 48 hours. Using 220 grit garnet sandpaper and sanding with the grain, sand the entire area just enough to make it feel slick. The best finishes are made by applying thin, even coats of finish and sanding thoroughly between coats. Vacuum the surfaces clean using a shop vac and proceed with your next coat. You'll probably need (if it's new wood) 3 to 5 coats of finish.
Be patient, mix your finishes thoroughly, follow the application instructions on the container and in a few days you'll have a nice finished floor and sore knees!!
Best of luck,
CD
johnCT
03-21-07, 07:38 AM
Thanks a lot CD! So the WB poly by itself will not discolor?
marksr
03-21-07, 10:57 AM
Water based polys go on clear [some a little milky] and dry clear with no change in wood color. Oil base polys/varnish deepens the various colors in the wood and ambers some [especially with time]
groundbeef
03-22-07, 10:42 AM
Actually, the WB poly MAY release the tannins into the finish, and either cloud it, or discolor it.
Just because it's a poly doesn't mean it won't intereact with the oak. If Minwax suggests a sealer to prevent it, I would look into it.
BTW on onsealed wood, why not use the oil? WB poly on a stairwell is certainly not the best solution. Oil base poly would offer much greater resistance to scratching, and wear. Granted, it smells worse, but wears better.
I never recommended WB poly for floors just for that reason. Now, if you were using white wash, thats a different story, as the main advantage to WB sealer is its non-yellowing qualities. But on naked oak, you won't even notice any yellowing.
Its not like you end up with stairs the color of a curb (think traffic yellow) in 6 weeks. It will end up looking more natural, and give the stairs a mellow look.
Anyway, thats my $.02
Just because it's a poly doesn't mean it won't intereact with the oak. If Minwax suggests a sealer to prevent it, I would look into it.
BTW on onsealed wood, why not use the oil? WB poly on a stairwell is certainly not the best solution. Oil base poly would offer much greater resistance to scratching, and wear. Granted, it smells worse, but wears better.
I never recommended WB poly for floors just for that reason. Now, if you were using white wash, thats a different story, as the main advantage to WB sealer is its non-yellowing qualities. But on naked oak, you won't even notice any yellowing.
Its not like you end up with stairs the color of a curb (think traffic yellow) in 6 weeks. It will end up looking more natural, and give the stairs a mellow look.
Anyway, thats my $.02
clockdaddy
03-22-07, 12:40 PM
Minwax is interested in selling any product the can and encourage several things that are unnecessary steps.
I think you have a point and this or any finish should be tested in a nonconspicuious place. I've used the finish for oak furnishings as well as walnut (which is also highly acidic) and never had a problem. Now, that's not to say it's not possible. Twenty years ago I wouldn't have recommended WB poly for anything!! The advances with it and other water-borne finishes during the last ten years are now generations ahead of what they were then.
Thanks for bring out a very good consideration.
CD
I think you have a point and this or any finish should be tested in a nonconspicuious place. I've used the finish for oak furnishings as well as walnut (which is also highly acidic) and never had a problem. Now, that's not to say it's not possible. Twenty years ago I wouldn't have recommended WB poly for anything!! The advances with it and other water-borne finishes during the last ten years are now generations ahead of what they were then.
Thanks for bring out a very good consideration.
CD