Rags are Better than Brushes for Oil Based Varnishes like Polyurethane
I think the easiest way to apply any oil based varnish like polyurethane is with rags. This works great with thick or with thin polyurethane, but thin varnishes are easier to manage. You can get a thin varnish by either using a wipe on varnish or by adding solvent to some thicker varnish. The type of rags that you select and exactly how you use them make a difference in how well they will work.
- Always use white rags to apply clear finishes because the solvent in the finish can pull the dyes out of colored fabrics. If that happens then the dye from the fabric can discolor the finish.
- My preferred fabric for applying finishes is something like tee shirt material. I usually buy a 5 pound bag of white rags, or sometimes I will buy a few yards at a fabric store. It’s ok if the material is a bit thicker than tee shirts as long as it is soft and lint free.
- I often start with a piece of fabric that is 8″-10″ square. I will use larger pieces on larger projects or smaller ones on smaller projects.
- This square of fabric is no longer just a rag. It is now a dedicated polyurethane applicator. It is important that it is flat and smooth without any wrinkles. Overlapping folds, wrinkles, and loose threads in the applicator can make it harder to apply a smooth and consistent film on your project. I always fold the edges and corners in toward the center to ensure that my applicator is working with me and not against me.
Folding the rag to avoid wrinkles and loose threads
Start with a square of fabric
Fold one edge into the center
Fold the opposite edge into the center
Turn the fabric 90 degrees and fold the next edge into the center
Fold the last edge into the center
Continue folding it into itself until the applicator is the appropriate size for the area that you are covering
Finally, pat the surface of the fabric with the sticky side of a piece of masking tape to remove any lint before wetting it with the polyurethane.
Applying Polyurethane with a Rag
Remove any dust from the board before applying the finish. I usually start by vacuuming the board to remove excess dust. A vacuum will still leave traces of dust on the board. Microfiber cloths have an electrostatic charge which helps to pull the remaining dust out of the pores. A tack cloth. is another great way to remove that last bit of dust from the wood.
Vacuum the board before applying the finish
A microfiber cloth really pulls the dust out of the pores
Dipping a brush or rag directly into the original container can introduce air and contaminants into the finish. Preserve what’s in the can by pouring the finish into a small container or bowl. Then charge the rag by dipping it into the bowl. Pouring the finish through a paint filter is an inexpensive way to keep any contaminants that might be in the can from messing up your finish.
Use a paint filter when pouring the finish into a small container or bowl.
Dip the applicator cloth into the bowl of polyurethane
It’s easy to get excess finish on the edges of the board. Starting somewhere towards the middle and working your way towards the ends will help to prevent this. It is also makes it easier to blend the finish into a smooth and consistent film.
It’s best to start somewhere towards the center and work your way out to the edges. This makes it easier to blend the strokes into one thin even layer of finish.
The first coat will soak in, so it’s OK to apply the first one a little heavy.
Sanding Between Coats?
It is only necessary to sand between coats if the previous coat is rough or if it has some other imperfections. I explain this more thoroughly in my article about polyurethane.
It’s easy to apply wipe on polyurethane in thin even strokes when using a folded rag as an applicator.
Placeholder photo until I have final
Continue adding coats of polyurethane until you get the look that you were going for.
Finish the finish
The most common wood finishing mistake that I see stopping after applying the last coat of finish. There are one or two usually easy steps left before you will see that perfect finish. And, that is something we call “Finish the Finish”. Even the most perfectly applied finish usually has just a bit of roughness on the surface. It might not even be visible, but you can feel it by gently moving your hand across the surface.
Fixing this is simple and easy, but it can make the difference between an ok finish and a perfect, fabulous wood finish.
It is best to wait until the finish is completely cured before proceeding. However, polyurethane takes up to 30 days to fully cure and I for one don’t have that much patience! Do let it sit for at least a day or two; hopefully a bit longer, but waiting just two days will improve your odds for success.
There are a few different ways to remove this small bit of roughness from the surface:
Burnish the surface with some paper. A brown paper bag is a good source of paper for this, but it is important that the paper is smooth because any folds or wrinkles in the paper can leave scratches. If you use paper for this then fold it similarly to the way that you folded the cloth applicator. Then gently rub it over the surface making sure not to over-do it. You will be surprised how much difference this can make.
Another way to burnish the surface is with white non-abrasive pads. Use these the same way as I described burnishing with paper (above). The not-abrasive pads are actually less aggressive than brown paper. So, this is a safer, but maybe less effective option.
I usually use very, very fine sandpaper. I prefer to use at least 5000 grit sandpaper, but 3000 grit works, too. Using sandpaper will cut the small nibs off, but burnishing as described doesn’t always remove them. Burnishing is more likely to push then down, than it is to actually remove them. It sounds like using sandpaper would scratch the surface, and if you were overly aggressive than it probably would. But, this very fine sandpaper is easy to use.
As with the brown paper, it is important that there are no folds or wrinkles in surface of the sandpaper. Then very gently move the sandpaper across the surface. By gently, I mean as gently as you possibly can. Barely harder than the weight of the paper itself. It is amazing how well, and how quickly this will clean up the surface of your finish.
The Last Step to a Perfect Wood Finish
The final step to a perfect wood finish is to add some wax. A coat of wax will ensure that your wood finish is buttery smooth. A coat of wax will also add a bit more sheen. Unless you want a dead flat finish, then a coat of wax is a welcome enhancement that significantly helps to the beauty the wood.
Most any paste wax will do the job and you probably won’t notice a difference from one to the next. My only caution is don’t use automotive wax because it can contain silicone or other chemicals that are not recommended for furniture.
A cheap can of paste wax will be visually just as appealing as the most expensive wax. One exception to that is Bees wax. It is a softer wax and it tends to have a slightly softer look, but it’s a very subtle difference that you might or might not actually notice.
A final thought
I hope that you are enjoying this Free Wood Finishing Class. I put a lot of time and effort into this, but I don’t mind as long as people are enjoying it. I have so much wood finishing content that it will take me a while to post all of it here on my website. Please let me know what you would like to see next!
