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

I started tacking between coats of poly 21 years ago, and doing this on your knees is the best way to clear that fine powdery dust that the vacuum cannot suck up. Let the solvent dry completely. Don’t coat over any solvent, this will interfere with the poly and cause bubbles. You want the second coat to be almost perfect. When the solvent is dry and before you coat the floor check for dust and debris one more time, with your hand. If it is still dirty, do one more tack ragging.

Now we come to the fun part, brushing on the finish. Yes I said BRUSHING. I quit using lamb’s wool applicators about 10 years ago, when I tried to clean one of these dirt collectors. After only 6 months of use (and cleaning between uses) I soaked it in solvent, and try as I might could not get all the dried caked finish globs and bits out of the interior of the lamb’s wool pad. Instead I purchased an 8″ Embee natural bristle brush, and have always been able to clean this free of all contaminants. I now also have a 12″ short bristle brush that I use on small jobs by hand. The longer nap Embee brush can be taped onto a pole and is almost as efficient as the old lamb’s wool applicator, without making the bubbles or leaving behind the junk. If you wish not to invest in $100 brushes at this time, I would recommend the 4″ Purdy brand bushes, with the unvarnished wood handle. You may have to spend 30 dollars on a brush like this but you will never wear it out.

Now here’s your floor-brushing lesson. Filter the finish into these large aluminum-roasting pans. I buy my floor finish in 5-gallon containers, so I just have to put a few layers of cheesecloth over the spout held on with a rubber band. You do need to filter these reactive type varnishes because they are always in some state of curing some dried film in the can. The older the can the more junk is in it. I pour the finish slowly into the shallow roasting pan, so I don’t create bubbles in the finish. The shallow pan will release the bubbles faster in any case than a deep bucket. If you are using a satin finish (which I always do) you will have stirred the finish gently before you pour, to mix up those flatteners.

Choose a game plan. You will want to do only a swath of finish that you can conformably reach across, so if your are applying the finish by hand with a brush don’t do more that a 3 foot by two foot area at a time. And if you are using that brush on a pole you can increase this to a 6 by 3-foot space. Of course each area will be one block in a series with the run with the floorboards. If this is parquet floor you will want your long swath of finish to be pointed at any windows, or parallel to a long wall. In either case keep the final brush strokes going always in the same direction for all coats. So, first wet the area by brushing in any direction, and then comb the finish once and only once in the chosen direction. You will have only brushed the finish twice, so have not created too many bubbles in the finish. You will have overlapped the previous area just a few inches, so as not to disturb this last patch too much either.

Do this slowly and deliberately, and if you are on your hand and knees (the best way to coat a floor if you have the really great Pro Knee pads). You should look at the light from the window reflected off the floor, this will show you what you really see what you have missed. Overhead lights, and coating a floor at night are not good at all. You need that angled light that only windows and strong sunlight can provide. I never start coating a floor past 2 PM. I just wait for the next day. Again I’m trying to tell you the best way to coat of floor, and if you are impatient, and rush through this second coat, you will have a lot more work to do before the third and final coat is applied. And if you are production floor mechanic I’m sure your eyes glazed over when you heard I brush on my finishes. Close the screen page now if you are too impatient to read this whole treatise. Your finishes will be forever bubbled and a pox on you.