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How I Apply Polyurethane To Cherry


This video and article are a deep dive into one method for finishing cherry that I quite like. If possible, I recommend watching the above video, though it is quite long, as I think you'll get a better sense of things like brush movements, and how thin to spread finish, and so on.

There are many ways to finish wood, and to finish cherry. This is just the way that I currently favour, when it comes to polyurethane. I work out of a basement shop, so I almost never use spray finishes, for reasons of safety and ventillation. I also almost use waterbased products exclusively for the same reason.

If you check the article links at the bottom of the article you can see some of my other web articles about finishing techniques for cherry.

Also, There are affiliate links at the bottom of this page, that you can use to find the products mentioned in this article, as well as some other finishing products which I've used.

Here are two sample cherry boards. The one in the front has been sanded with 80 grit sandpaper. The one in the rear, has been sanded first with 80 grit, and then again with 150 grit sandpaper.

You need to touch the wood to tell the difference. Both look fine, but the 80 grit surface is noticeably rough.. I start with 80 grit if I need to clean up tool marks, or if there is glue residue, or so on. It is the first pass. I then take a second pass with 150 grit sandpaper, which leaves a beautiful smooth finish.

I usually stop at 150 grit. Some people like to go further, going to 220 grit or more. But I find that this is good enough for my tastes, and polyurethane is a film finish, so it will cover over things.

End grain really can soak up the finish, and as such you want to pay particularly close attention to it when sanding. Often you will sand end grain one step finer (ie: go to 220 grit) than the rest of the project.

Waterbased polyurethane finishes are usually are milky white, and dry clear. I really like the Minwax Oil Modified polyurethane, which has a slightly darker tone in the can. Despite the name, it is a waterbased finish, but it gives that hint of amber colour that oil finishes are known for. This is my current "go-to" polyurethane.

Also in this photo you can see the yellow "Painters Pyramids" that I use when finishing. Something like this is essential if you want to be able to apply finish to BOTH sides of your work in one session. I apply finish to the non-show side, then flip the project over to apply finish to the other side. You need some sort of minimal contact method to support the still-damp side of the project. You can also use something like scraps of wood with nails/screws projecting through -- see the black board in the background. I used those for years. However I eventually decided to try the painters pyramids and I now use them all the time. They're light, they don't tip over, and they are all identical, so they are all exactly the same height. I bought mine at Lee Valley, but they are also easily found on Amazon and probably elsewhere. (I have affiliate links at the bottom of the page.)

I like to use inexpensive foam brushes. Do not overfill the brush. Just let the foam soak it up. If there is excess finish, just let it drip out of the brush into the can. DO NOT wipe the brush on the lip of the can, just let it drip. DO NOT "squish" the brush against the can either. You do not want to introduce any bubbles into the finish.

I tend to work with very light amounts of finish, as I would rather have to put on another coat, than to deal with drips and runs that you risk with a heavy coat.

Here I am laying on the first coat of poly onto a sample board of cherry. Just lay it on gently, and go back over it maybe once to smooth it down. Everyone always warns you not to "overwork" a waterbased finish. My perspective is that there is just no need to do much working. Just brush it out, look to make sure you have it covered, and then maybe touch up any spots that look like they might need some smoothing.

I usually wait till the brush is mostly used up before I apply finish to the sides. I really don't want drips. I will often run the empty brush along the bottom corner of the piece, as shown here, after I've applied finish, to try to catch any drips or runs that might be starting.

After the first finish has fully dried, I will sand it lightly with 220 grit paper. You must sand. The finish will raise the grain, and it will feel rough. You always need to sand between coats, but each successive coat requires less.

While applying the finish you will want to lean over and look at a sharp angle across the finish. Having a strong light will help. Look for spots that are missing finish

This blurry photo shows how, after I've completed applying finish to the back side of these drawer fronts, I pick up the boards by the sides, which have not been finished yet, and flip them over onto the Painter's Pyramids, so I can apply finish to the other side.

This is a photo of me preparing for the 3rd coat of finish. The process is roughly the same, but I switch to a lighter grit of sandpaper for the 3rd and subsequent coats. I'm using 320 grit paper here, and I'm sanding very lightly. Just touch the piece and you'll see how rough it feels. BUT EVEN IF IT FEELS SMOOTH you must do some light sanding/scuffing between coats of polyurethane, in order for the coat to properly adhere.

Here is a large drip of finish that formed after the second coat. I deal with that by pulling out a chisel and using that to slice off the majority of the drip.

(Next photo) I then turn the chisel vertical and use it to scrape away at the remnants of the drip until I don't see OR FEEL anything. If the drip is tiny -- like just small bubbles in the finish -- then I would use this as the first step.

(Second photo below) Finally I pull out the sandpaper and sand the area smooth. It is now ready to be re-finished. You might even sand through back to bare wood when dealing with a drip, which is one reason why you want to minimize drips. However, since this is just a clear coat of poly, with no stain, it is really easy to fix. Just apply more poly. There is no scraped-through stain to repair, it's just a clear coat. It's pretty easy to apply a bit more.

Each coat of finish will require less finish, as the wood no longer soaks it up. Here is a photo of me applying the third coat, and in this instance I only dipped the brush in the finish twice, and had enough in the brush to finish the entire side of these large boards.

Some of the Tools/Supplies Used In This Project: (Affiliate Links)


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See Also:

Aging Cherry With Lye

Cherry Finish Test