Polyurethane Varnish Love It or Hate It

Oil based polyurethane is the perfect finish for tool handles like this knob & tote set and it doesn’t have to look like plastic.

I like polyurethane varnish. There, I said it and I mean it.

I’m sure at one time or another we have all heard that “‘poly’ gives wood a plastic look”. What if I were to tell you that that is simply not true? Well, it isn’t true. I use polyurethane varnish professionally on a regular basis and I have never had a customer complain. You can surely end up with that plastic look with polyurethane if you don’t use it properly. Poly’ is like any other tool in your tool bag. When used properly it can be a dream and if not it can be downright ugly.

Let’s take a look at what varnish is actually made of. The main components of any varnish are, resin, a binder, and a solvent. Now there are a lot more chemicals used in the manufacture of varnish by different manufacturers, but these are the main components of all modern varnishes. The main resin used in modern varnishes is urethane or polyurethane, which is a mix of different types of urethane resin thus the poly designation. Before the use of urethane resin most varnish manufacturers used phenolic resins, and some still do, however, the overwhelming majority of modern varnish makers use urethane resin so it is pretty hard to find a varnish that isn‘t polyurethane based. The binder in modern varnish is usually linseed oil and mineral spirits are most often used as the solvent.

Polyurethane varnish offers a very hard, moisture resistant finish which is just what you want for your furniture isn’t it? In order to avoid that plastic look thin your polyurethane varnish at least 50:50. For the first coat or two a 40:60 mix of varnish to thinner is even better. Oil based polyurethane varnish is thick and it has a tendency to sit on the surface with subsequent coats building to that plastic look you want to avoid. By thinning the first coat or two heavily the varnish is allowed to penetrate the wood. Two or three more coats thinned to 50:50 will afford all the protection you need without the build up that full strength varnish gives.

Another thing you can do to avoid the plastic look when using polyurethane varnish is to stay away from high gloss finishes. The high gloss polyurethane varnish can have a tendency to look like plastic. Leave the high gloss finish to the French polish. French polish is a method of finishing that achieves a very high gloss with very little build. It is the heavy build of finish that gives that plastic look. When using polyurethane varnish I stick with a satin sheen. This imparts a rich appearance with none of that plastic look.

The picture above shows a plane tote finished with oil based polyurethane varnish. It doesn’t have that plastic look. I use polyurethane on these totes because they are in severe service and need a hard durable coating that will stand up to body oils, grit and abrasion. Don’t perpetuate the falsehood of polyurethane as so many people have done. Get a small container of good quality satin sheen oil based polyurethane varnish. Thin it as I have described and try it out on a small project. You will find that polyurethane can give you a first class furniture quality finish that is hard, durable and moisture resistant and you will have another tool in your finishing arsenal.

As always thanks for stopping by and please feel free to leave a comment.

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About R & B ENTERPRISES

Professional furniture maker and restorer. Dealer and collector of vintage and antique woodworking tools.
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2 Responses to Polyurethane Varnish Love It or Hate It

  1. J. Pierce says:

    thanks for the comments, Bill. Finish can be hard to do right, and sometimes it’s tempting to ignore the parts that are “less fun” for some folks. I love oil finishes for some things to, but it strikes me that the when folks give up on poly after a couple bad experiences and just switch to something easier but less durable, it’s like giving up on dovetails after a failed attempt and just using rabbet joints on every drawer – rabbet jointed drawers are fine sometimes, but you have to know what a project needs and when, and lot of times it’s worth slogging through learning a new skill to get the most out of whatever you’re doing.

    also – I have some of your handles on one of my Miller Falls, and I love the finish – not only does it look and feel great, it’s held up awesomely. I’m tough on my plane handles, I guess, because my Lie Nielsen is already pretty grimy, and pretty much bare wood at this point. The finish on your handles is still holding up, and hasn’t been treated any different (and that plane probably gets more use) To say nothing of the quality of the handles themselves.

    • Thank you for the kind word Joshua. You may be interested to know that I am working on tote and knob sets for the LN planes right now. I don’t know what type of finish LN uses on their wood, but mine will use polyurethane. The lesson here is not to take someones word for things. Try things for yourself. Don’t perpetuate falsehoods.

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