How to Apply Marine Varnish

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Wood sealed with marine varnish exhibits the colour and beauty of natural grain. Marine varnishes are usually re-coated annually. They are relatively high-maintenance and proper care requires attention to wear, use and ageing issues. Recoat varnish before you have issues like cracking and peeling and you will save time and effort in the long run. Prepare the surfaces properly and apply the varnish when temperatures are moderate for the best results.

Skill level:

Things you need

  • Heat gun
  • Putty knife
  • Detergent
  • Bleach
  • White spirit
  • Masking tape
  • Marine varnish
  • Sandpaper (120- and 220-grit)
  • Foam brushes

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  1. 1

    Remove old varnish if the finish is peeling and bare wood is showing. Chemical strippers are toxic and messy -- use a heat gun and putty knife to peel off old varnish. Be careful not to scorch the wood (>

  2. 2

    Clean the wood. Use a commercial wood restorer, brightener or cleaner, or household detergent. Get rid of any stains or discolouration and rinse well.

  3. 3

    Wipe down the wood with bleach. This will kill any mould or mildew that can crop up under the new finish. Dilute the bleach with water according to the manufacturer's instructions -- don't apply straight bleach to the wood.

  4. 4

    Wipe with white spirit. White spirit will remove any grease or silicone that will cause the new finish to lift off the wood.

  5. 5

    Sand the wood. First use 120-grit to get out lifted grain and stains, then finish sanding with 220-grit.

  6. 6

    Mask the area. Use masking tape to cover up any surfaces you don't want varnished.

  7. 7
  8. 8

    Recoat the finish. After the manufacturer's suggested drying time between coats, apply at least two more coats.

Tips and warnings

  • Don't wait for the finish to start peeling before recoating. Annual coating is necessary. Sand unblemished varnish with 180- or 220-grit sandpaper and wipe with white spirit before applying a new coat. Built-up finishes should be completely removed every five or six years.
  • It is easier to apply varnish under conditions of low humidity and moderate temperatures (15.6 to 21.1 degrees Celsius). The varnish will stick better to the wood and drying time will be long enough to allow the varnish to settle into a seamless finish.
  • Read the manufacturer's safety instructions for all products you use. Follow protocols for safety including protective clothing and disposal of unused material.

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