How to apply oil based polyurethane WITHOUT the pits and bubbles.

I solve this by applying a furniture quality “fast dry” wiping stain. I use a local manufacturer’s proven product. It has the advantage of drying in the lighter colors in about 4 hours, and the darker colors always dry overnight. The quick drying solvents in this type of stain make it a bit trickier to use. It contains fewer binders, so you have to be really careful the next day when you walk on this stain. The poly, if brushed too vigorously, will wipe away this type of stain. But I am a seasoned professional, and can handle these limitations. I can in most cases, stain and coat the same day. I always apply the stain with lint free rags, and vacuum after the stain is dry, and brush on the poly full strength. The reason for this full strength coat is simple; I have to build my finish over the stain quickly, so that when I scuff sand (or screen) between coats, I won’t rub out the stain. The binder in the stain has helped fill the wood pores a bit, and the extra fine sanding has made the first coat of poly on the stain go on quite smoothly. So in this case never trowel a finish over a wood stain, and never add thinner to it either. I’m going to do a separate article on sanding and staining floors, once I get enough requests.

And now, once you are quite certain that the fist coat of finish is quite dry, you can proceed in the screening. Use your buffing machine with the handle low to the floor, you don’t want to gouge too much finish off the wood, after all this is only a thin coat. If you have stained the floor, and are buffing the first coat, you must take even more care. Run the buffer in a corner first, and I suggest you dull the screen by sanding the screen itself. See if you are removing too much finish and are thereby removing the stain to the bare wood. This is a delicate operation. On the one hand you want to scuff the finish. Poly just will not stick to itself otherwise. But you don’t want to sand though the finish into the delicate stain. You may have to hand screen the floor instead. That’s why I always apply a smooth but heavy (500 sq. ft. per gal.) coating over my dried stains. But I still take care, and that’s why I charge almost double to sand and stain a floor. It’s a risky job.

Run the buffer in both directions never stopping in any spot, just a nice easy back and forth motion. Go with the run of the wood, and then repeat again against the run of the floorboards. This assures you that all low spots on the floor will have the finish well scratched. Next, get on your hand and knees and scuff sand the floor in all the areas that the buffer couldn’t reach, and make sure to go all along the edges. This gives you a chance to see if all the pits, lumps and blobs are sanded down smooth and flat with the surrounding finish. You may have to gently scrape out some blobs, and really sand those pits until they are not visible. The more fussy you are now the better the next coats will come out. This is precisely why you need a really dry finish; else all this scuff sanding will just make a gummy mess. Be patient.

One you have a 100% scuff sanded finish, and it feels as smooth as a baby’s behind, you can start cleaning up. Vacuum twice again, with your industrial vacuum. Get into all the corners of course. Now you can tack rag the floor. I use white lint free rags (yes you can get lint free cotton rags at most big box stores, expensive but worth it). Choose the most lint free in rag in the box, and wet it well with paint thinner. In this case paint thinner is just right, it dries at just the right rate for cleaning the floor. Fold the rag in a long narrow bundle and using both hands on your knees wash the floor in a back and forth sweeping motion as you crawl backwards. I wear my ProKnee kneepads so even after 23 years on the floor; I can still do this with comfort. And hey, I’m not here to tell you the easiest way to prep a floor, just the best way.