paint and varnish

When it comes to finishing your project, it is not as simple as it used to be. A good quality exterior house paint was once a common recommendation, but coating technology has moved on significantly. There are now many options depending on the finish you want, your budget, skill level and equipment available.

Two-pack products can provide a very hard, durable and high-quality finish. They can also be more difficult to apply and repair, and many are best suited to spray application. Because they cure very hard, they are generally less tolerant of movement than softer coatings.

In our workshop we predominantly spray professional-grade two-pack products when we are aiming for an automotive-quality finish. This type of finish requires suitable spray equipment, careful preparation and experience, so it is not always practical for the amateur builder.

It is also worth keeping in mind that some linear polyurethane products cannot easily be polished or buffed. This can make minor application defects more difficult to correct after the coating has cured.

Single-pack polyurethane

For most amateur builders, a marine-grade single-pack polyurethane is an excellent middle ground. These products are easier to apply than two-pack coatings and can produce a very good finish using the roll-and-tip method.

For most applications, our recommendation is a good quality marine-grade single-pack polyurethane applied using the roll-and-tip method.

International offers a range of marine paints, primers and varnishes suitable for this type of work. If a suitable single-pack polyurethane is difficult to source, a good quality marine-grade paint is another practical option.

Varnish

Varnish is normally used where you want to retain the natural appearance of the plywood or timber. As well as providing the final appearance, varnish protects the epoxy underneath from ultraviolet light.

Epoxy itself has poor resistance to prolonged UV exposure, so epoxy-coated timber that will be exposed to sunlight should be protected with either paint or a suitable UV-resistant varnish.

Marine varnishes are readily available from marine suppliers, paint stores and many hardware stores. We have previously used products such as Bondall Monocel marine-grade varnish and Feast Watson Spar Marine varnish with good results.

As with paint, careful surface preparation and thin, even coats are important. Varnish can also be applied successfully using the roll-and-tip method.

Surface preparation

The quality of the final finish depends heavily on the preparation underneath it. Paint and varnish will often highlight defects that were difficult to see while working on the bare epoxy surface.

Before applying paint or varnish over cured epoxy, make sure any amine blush has been removed. Wash the surface thoroughly with warm water and a Scotch-Brite pad, dry it with clean paper towels or rags, then sand the surface to provide a mechanical key.

See our Working with Epoxy Resin page for more information about amine blush and preparing cured epoxy for secondary bonding or finishing.

Continue fairing and sanding until you are satisfied with the surface. A high-gloss finish will make hollows, sanding marks, epoxy runs and other imperfections much more obvious.

Roll and tip

The roll-and-tip method is one of the easiest ways to achieve a good paint or varnish finish without spray equipment.

  • Apply a thin, even coat with a suitable foam or short-nap roller.
  • Work in relatively small sections so the coating does not begin to cure before it is tipped.
  • Immediately follow the roller with a good quality foam brush or suitable tipping brush.
  • Use very light pressure when tipping. The purpose is mainly to remove bubbles and roller texture.
  • Maintain a wet edge as you work.
  • Do not keep going back over an area once the coating has started to tack off.

Several thin coats will normally produce a better finish than trying to achieve full coverage in one or two heavy coats. Follow the paint or varnish manufacturer’s instructions for recoating and sanding between coats.

Stain

If you are considering staining plywood or timber before applying epoxy, make sure the stain is compatible with your epoxy system.

Mohawk Ultra Penetrating Stain, previously sold as Behlen Solar-Lux, is one product that has been used successfully for this type of work. Other suitable products may also be available.

Producing an even stain finish on plywood can be difficult, particularly where different sheets or timber species absorb stain differently. Always test the complete stain, epoxy and varnish system on scrap material before applying it to the boat.

Other tips

  • Preparation: Spend the time getting the surface right before applying the first finish coat. Gloss paint and varnish will make defects more visible, not less.
  • Thin coats: Paint and varnish generally flow and cure better when applied in several thin coats rather than fewer heavy coats.
  • Cleanliness: Keep dust, silicone, oil and other contaminants away from surfaces that are ready for coating.
  • Temperature: Follow the coating manufacturer’s recommended application temperature and recoat times.
  • Test first: If you are combining products from different manufacturers, test the complete coating system on scrap before committing to the boat.

Further information

Chesapeake Light Craft has detailed information covering the preparation, painting and varnishing of epoxy-coated wooden boats:

Videos