How to Varnish Like a Pro

Preparation for varnish work

To achieve a good finish, the condition of the existing varnish should be thoroughly checked to determine the extent of the preparation required.

  1. Look for areas of damage, separation or peeling or any other signs that the varnish does not have a firm hold on the substrate.
  2. Clean and prepare the surface by washing with Special Thinner 216 to remove any contamination. Then inspect again to ensure no damage has been missed.
  3. Depending on the condition of your wood, there are three categories to separate the different steps needed for you to varnish like a professional.
    • Varnish, good condition and no damage
      Sand with 220-320 grit wet-or-dry sandpaper and when dry, wipe with a cloth dampened with 333 (2333N if varnishing with Perfection).
    • Varnish, good condition and some damage
      These areas may be repaired using Interstain Paste Wood Filler Stain. Spot priming, spot varnishing and sanding may then be required prior to the full varnish job.
    • Varnish, poor condition
      If the previous varnish coating is cracking, peeling or showing signs of separation overall, it should be totally removed by either scraping, sanding or stripping with a chemical paint stripper such as Interstrip 299E.

Applying the varnish

  1. We recommend that the first coat of varnish applied is thinned up to 15-20%. This will promote good penetration of the surface and adhesion of subsequent coats.
  2. After the first coat has been applied, the surface will appear rough. This is a result of the exposed ends of grain absorbing the varnish and lifting. Sand smooth with a 220 grit sandpaper.
  3. Applying varnish with a brush is usually the best method, although roller application can be effective on large flat surfaces.
    • Brush out the varnish with firm strokes along and across the grain holding the brush at 90 degrees to the surface. Then tip-off by gently stroking the surface with the brush at 45 degrees.
    • Your brush should be used for varnish only.
  4. A minimum of three full unthinned coats is recommended for all varnishes. However, to achieve long lasting protection, you should plan to apply up to ten coats, depending on the system. As the number of coats increases, sand in between to increase the level of gloss and depth of luster.

The information provided here has been reproduced courtesy of Interlux. Wholesale Marine reproduced this information 08/14/2009.