How to Sand Spar Urethane

Properly Sand Spar Urethane

• 1

  Sand the surface smooth before the application of the spar urethane. The smoother the wood, the better the resulting finish.

• 2

  Apply the spar urethane. Spar urethane can be thinned with paint thinner or mineral spirits. A thinner mix may result in a smoother finish. If thin enough the spar urethane will level itself and erase brush or rag marks. Multiple applications of the spar urethane may be required.

• 3

  Sand the spar varnish between each application of the spar urethane. Allow the finish to dry and sand lightly with the finest sandpaper available (320 grit). Only sand with the grain of the wood. Do not over-sand. The idea is to smooth the previous coat of varnish, not sand it away.

• 4

  Apply the last coat of spar urethane with a lint-free rag. The wood is not sanded after the final application of the spar urethane.