Finishing is hard. You spent hours matching the grains, cutting and fitting, perfecting joints, sanding to mirror perfection, and then you apply the finish and the trouble starts. You end up with bubbles, brush marks or worse. It’s easy to blame the brand of finish but the reality is that most problems involve operator error. They usually have very specific causes that can be remedied without buying more finish.
The first key to success is a clean work area. You can’t get a flawless finish if there’s dust in the air or dust on your project. Start by cleaning the project and the work area thoroughly. Its best to wait a day after sanding and cleaning to be sure all the dust particles are out of the air. Even be sure you have clean, dust-free clothes. Any ambient dust will result in nubs in your finish that will have to be sanded smooth and recoated.
Here are some other common finish problems and fixes:
- Brush marks occur when the finish is too heavy and can’t flow out and level or if you go back over finish that is already drying. Avoid them by adding enough of the appropriate thinner to allow the finish to flow. To remove brush marks, sand with 220 grit sandpaper and recoat with thinned finish.
- Runs and sags are caused by gravity. You can avoid them by applying thinner coats, especially on vertical surfaces. If you get a drip, wait for the finish to dry before working on it. Otherwise you may expand the problem by leaving brush marks over a wider area. Scrape the excess off with a razor blade and/or sand it down with 220 grit sandpaper. Once the surface is level you can recoat.
- Cracking or crazing is caused by too heavy application. It can also happen when working in hot conditions, causing the finish to dry too quickly. Sand the area with 220-grit sandpaper and recoat. If temperature was a factor, wait until the temperature drops and then spread a thinner coat.
- Uneven sheen occurs when the particles used to flatten the sheen are not evenly distributed before the finish is applied. Stir thoroughly and often during the finishing process.
- Finish won’t dry or harden after the recommended drying time. It feels gummy or tacky. Causes may include a work room that is too cool or naturally oily wood that interacts with the finish. Try raising the room temperature. If doesn’t dry you’ll need to strip the finish. If the problem is oils in the wood, try wiping with naptha just before applying finish. Or seal it first with shellac or a fast drying spray lacquer and then recoat with your finish as needed.
Those are common finish problems. We’ve all been there – a bad finish can really ruin your day. But don’t let the difficulty of finishing keep you from starting. With some extra care and attention you can get those special holiday projects ready in time.
