How do I get the best results from my varnish?

If you’re applying over an existing varnish, ensure the surface is sound, if not the coating should be removed. Test for compatibility – To test if an existing topside paint product, or a varnish, is compatible with our two-part polyurethane products; tape a cloth soaked in Thinners No.9 to the previously painted substrate for 24 hours. If the surface is softened, it is probably not compatible. In this instance, unless stripping down to the bare substrate is an option, a one-part product should be applied. For bare wood, unless you’re using a clear surface primer, such as Interlux Clear Wood Sealer Fast Dry, we recommend thinning the first coat of all our varnishes. This promotes good penetration of the surface and adhesion of subsequent coats. After this first coat, the surface will appear rough – as the exposed ends of the wood absorb the varnish and lift – sand this smooth with a medium grit sandpaper.

Hints and tips?
  • Round the edges of any scrapers with a file to avoid gouging
  • Keep the sandpaper clean and change it frequently
  • Sand by numbers, finishing the surface with a progressively finer grit of paper
  • Varnishing is best achieved on warm, dry mornings – cold weather slows drying and moisture spoils the gloss
  • Always use a clean brush, previously used only for varnish
  • Always buy the highest quality varnish and brush available. This will ensure you achieve the most attractive finish
  • Clean new brushes before use
  • Test the finish on a spare piece of wood before applying to the boat
  • On large areas use a foam roller to apply the initial coat, followed immediately behind with a wide brush for the finishing strokes – this is best done by two people
  • After cleaning with the correct thinners, wash the brush in detergent and warm water, dry and wrap in greaseproof paper in a fine chisel shape
  • Alternatively, having cleaned and washed the brush, suspend by its handle to avoid any ‘fishtailing’ of the bristle
  • As the varnish ages in the can you may find there are lumps or contamination. Sieving the varnish into a separate container through cheesecloth, a paint filter or an old stocking is a good solution to this problem
  • Never apply direct from the can, as this will introduce contamination
  • Always pour the amount of varnish that you expect to use at any one time, into a separate container
  • Don’t use varnish which has been open for a long period as it will have picked up dust
  • Do not varnish wood when exposed to direct sunlight
  • Never leave bare wood exposed too long as it will absorb moisture from the atmosphere