Flexner on Finishing

How to avoid them and then fix them when they do occur.

Fixes for common finishing problems.

No matter how experienced or good you are at wood finishing, you‘ll still have problems now and then. Here are some of the most common and how to avoid and fix them.

Brush Marks and Orange Peel

Brush marks and orange peel are the problems that cause woodworkers to like the wipe-on/wipe-off finishes so much. Finishes such as oil, wiping varnish and wax are essentially foolproof. The problem is that they are too thin to offer much protection against moisture.

So how can you eliminate or, at least, reduce brush marks and orange peel to get the maximum protection? The easy solution is to thin the finish more. This is pretty logical, actually. If the finish were just the thinner, the problem would be solved. There wouldn’t be any build, so no brush marks or orange peel. It follows that thinning to somewhere between the thickness that is causing the problem and just the thinner should produce minimal brush marking and orange peel while still producing adequate thickness.

If you are spraying and using a compressor rather than a turbine, you can also turn up the air pressure. Doing this will atomize thicker finishes better. I have not found that using a more expensive brush eliminates brush marks. They happen anyway.

Fixing brush marks or orange peel after they have occurred is also pretty logical. Sand the surface level and brush or spray another coat that is thinned more.

The Finish Won’t Dry or Harden As It Should

The most common reason finishes dry slower and sometimes never reach the hardness you expect is working in cold conditions. So figure out a way to warm the area you’re working in.

There are also some other things you can do depending on the finish you’re using. You have more control of the drying with lacquer than other finishes, which is one of the reasons lacquer (including catalyzed lacquer) is popular with professionals. To speed the drying of lacquer thin it with acetone rather than lacquer thinner. Acetone evaporates much more rapidly than lacquer thinner, so the finish dries quicker.

With shellac you don’t have a choice of solvents you can use. The usual cause of slow drying, other than working in low temperatures, is using shellac that is too old. Unlike lacquer and varnish, shellac has a shelf life. It used to be that Zinsser Bulls Eye, the only remaining supplier of already-dissolved shellac put the date of manufacture on the can. They no longer do this. So your choices are to go to another store or catalogue that you think has a faster turnover so the shellac will be fresher, or dissolve your own shellac from shellac flakes and use it within a year or less.

Varnish, including polyurethane varnish, and water-based finish that

1 Brush marks occur when the finish is too thick (left). So thin the finish more to eliminate them. You may have to apply more coats to get an equivalent build.

2 Orange peel occurs when you spray a finish that is too thick (left). To eliminate orange peel, thin the finish or increase the air pressure to your spray gun.