Simple polyurethane finish is tough and pretty

A lot of folks build nice wood projects only to struggle when applying a finish. The trouble is that the instructions on the back of the can are pretty sketchy. Here’s what they don’t tell you, and don’t worry, it’s no big deal. Follow these steps and you’ll leave the wood glowing and the surface buttery to the touch.

First a bit of context. Basically there are two types of finishes: thin oil finishes that make the wood pretty but don’t build up much protection, and film finishes like polyurethane and shellac that also beautify the wood but also build up a protective layer. Choose a film finish for any project that will see some wear and tear, like the coffee table in this blog.

Polyurethane is the easiest film finish to use. First of all, choose the quick-drying, oil-based kind. The only reason to use water-based poly is if you want the wood to end up whiter looking (water-based dries very clear, but isn’t as durable; oil-based is tougher but has a slight yellowing effect, which is nice on most woods.) Secondly, choose the satin type. It won’t end up shiny and sticky looking like gloss poly does.

After that, the main keys to success with any finish are all about sanding–before you apply it, and between coats. Get that right, and watch for drips along the way, and you’ll be amazed at how good your new project looks. Here’s the path to happiness.

A good finish is all about wood preparation. Sand up through the grits, from about 120 or 150, depending on how rough or bumpy the wood is, to 220 grit. Use a sanding block under the paper or a random-orbit sander like this one. It doesn’t matter which. Just be systematic and thorough.
A piece of flexible rubber mat makes a good backer for sanding these curved edges.
Satin polyurethane has a flattening material in it that makes it less glossy, but this stuff will settle to the bottom of the can. Stir well before starting, and occasionally as you go.
Disposable foam brushes work well for polyurethane. Elevate a panel like this and don’t try to do the bottom until the top and edges are done and dry. Dip the brush, unload it in a central area, and then spread the finish out with smooth strokes.
To avoid drips, make sure there isn’t too much finish in the brush when you get to the edge, and fly off the edge lightly.
Edges are next. To avoid drips below, you probably don’t even have to dip the foam brush again before doing these edges. If you do, dip it lightly.
Just to be sure there aren’t any drips hanging below, I wipe the underside of the edges with a clean paper towel. Now let the panel or project dry before flipping it and doing the surface or surfaces you couldn’t get to. Same process for those, even if that means finishing the edges twice.
Sand between coats! This is a critical step that a lot of people pass by. The first coat will raise some wood whiskers and be pretty rough, so hit it lightly with 220-grit paper and a sanding block just until it feels smooth. Then wipe, blow, or vacuum away the dust. That’s critical too.
Next coat is just like the first coat.
You’ve got just one more coat to go for most projects. Before this one, fold up the 220-grit sandpaper and hold it in your hands as you make a light pass over the project. This way you’ll be sure to get into little valleys that a sanding block might miss. Then get rid of the dust, apply that last coat, and enjoy!

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