At First Blush

by Alan Noel

With the way things are going here in the Southeast, with virtually no humidity in the air, no rain, and temperatures on the rise, applying most any finish in this environment should surely go very smoothly without any drying problems, other than a little dust that might find its way into the finish.

Usually though, particularly in the South, but all over the U.S.A. as well, heat and humidity can cause a few problems. Such as when finishing materials like shellac or brushing lacquer dry too fast and do not flow out smoothly; or varnish dries slowly and unevenly when the humidity is very high and there is virtually no air movement; or worst of all, blushing.

Blushing occurs when moisture gets trapped in the finish due to condensation and as a result gives the appearance of a whitish, cloudy haze. Blushing occurs most often when using lacquer or shellac because of their very fast drying characteristics that can trap moisture during the application process.

    Here are some tips to help with these problems:

  • Safety first. Work in a well ventilated area.
  • To even out the drying of varnish, place a fan close to the project, blowing away from it. Air movement is the most important thing to remember when it comes to oil finishes.
  • After drying, sand and apply another coat of finish with a little mineral spirits added to slow down the drying time and to aid flow out.
  • When using shellac, an easy way to slow down the drying is to add one ounce of pure gum turpentine per quart of shellac. Be sure to use pure gum turpentine, not a petroleum substitute.
  • Brushing lacquer is best slowed by adding a lacquer retarder specifically designed for the particular product you are using, although most any brand name product can be used with good results by following the instructions on the can.
  • When working with lacquer, allow the finish enough time to dry thoroughly. Often the blush will disappear after the film has dried completely.
  • If blush remains in the lacquered finish, it can be eliminated with a light rubbing with fine steel wool or a gentle wet sanding with mineral spirits and very fine sandpaper. Also, an additional top coat of lacquer will make the blush disappear.
  • A dried shellac finish can be gently rubbed with a lint free cloth and denatured alcohol to soften the finish which will allow the blush to escape, or an additional top coat will do the same.
  • Unfortunately, if none of these steps work, you will have to strip the finish and start over or seek the advice of a professional.
See Previous Newsletters Subscribe to Our Newsletter

Copyright © 2007 Highland Woodworking, Inc.

Highland Woodworking | 1045 N. Highland Avenue, NE | Atlanta | GA | 30306 | 404.872.4466