Few things are as quintessential to the archetypal sailboat as gleaming, iridescent woodwork that is indicative of a recent coat with one of the best boat varnish products on the market.

Choosing a product and methodology to apply marine varnish to achieve such results is not as simple as it would seem at first glance however, and this guide aims to make the whole process easier for novice and seasoned boat-owners alike.

First things first, what exactly is boat varnish? Put simply, varnish is a chemical solution of three parts which includes a penetrating oil, resin, and solvent.

Boat varnish for exterior use, aka. “spar varnish” — aptly named because it was designed and envisioned as a flexible protective coating to protect a yacht’s wooden spar in the harsh (outdoor) marine environment — both protects and beautifies a vessel’s wood parts.

It does so by sealing the wood with a somewhat hard, yet flexible, clear protective barrier that can last up to three years of UV and element exposure in temperate climates for the most durable two-part product formulations.

These days, most high-end boat varnishes use tung oil and an alkyld or polyurethane resin. Of the two types of resin, polyurethane — either one or two part — is going to be much more durable and resistant to UV, abrasion, fuel/solvent spills, and impacts.

While a two-part product cannot be applied over a one-part product, a two-part product is going to last much longer and be far more durable. Hence for high traffic areas like cabin soles, a two-part polyurethane product cannot be beat for longevity and durability.

Boaters should be aware that the most onerous task of applying boat varnish is the surface prep, which requires removing all flaking previous coatings by sanding, washing with solvent to degrease the surface, in addition to taping nearby areas to keep the varnish off.

Because of that, I highly recommend using quality products over cheaper, lower cost options which will mean your boat needs revarnishing far more often.

International Perfection Plus two-part varnish

Best polyurethane boat varnish

International Perfection Plus (sold in the US under the Interlux brnad) is arguably the best overall marine spar varnish on the market. This two-part polyurethane formulation is not only the most aesthetically spectacular, but also the most durable and longest lasting when exposed to UV.

This two-part product is applied to bare wood after careful sanding and degreasing and can be rolled/brushed or sprayed. It uses a proprietary Interlux thinner and one’s results will be excellent if one follows the recommended procedures to the “t.”

Of all the boat varnish products on this list, this two-part product is probably the least DIY-friendly.

Reasons to buy

• Most durable marine varnish in terms of hardness and flexibility
• Best UV resistance
• Most beautiful (glossy) varnish if applied properly
• Hardness and longevity makes it a prime contender to redo cabin soles and floor boards (after proper surface prep)

Reasons to avoid

• Difficult application for inexperienced laymen
• Expensive

Buy International Perfection PLUS two-part varnish on Amazon (UK)

Buy International Perfection PLUS two-part Varnish on Gael Force Marine

Buy Interlux Perfection PLUS two-part varnish on Amazon (US)

Buy Interlux Perfection PLUS two-part varnish on West Marine

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Epifanes clear varnish

Epifanes offers quality marine paints and varnishes at reasonable prices and their Clear High Gloss Varnish is no exception. With 64% solids content (tung oil) and an alkyd base, this varnish is sure to be brilliant in terms of gloss with reasonable durability and longevity.

With one-part alkyd products, boat owners can expect up to two years of protection before maintenance is required if left out in the elements year-round. This product can be brushed, rolled, or sprayed.

Reasons to buy

• Affordable, quality one-part product
• High solids content results in very glossy finish
• Relatively easy to apply and achieve satisfactory results

Reasons to avoid

• Not as much UV protection as other offerings
• Not as impact or abrasion-resistant as other offerings

Buy Epifanes Clear Varnish on Amazon

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International Schooner Premish Varnish

A traditional marine spar varnish — albeit a good one — is Interlux’s Schooner Varnish.

With an alkyd base, 47% of tung oil solids, and UV inhibitors to boot, this product is a well-balanced one-part product that is suitable for a variety of uses. This product can be brushed, rolled, or sprayed.

Reasons to buy

• Affordable, quality one-part product
• Well-balanced product in terms of UV protection and solids content
• Relatively easy to apply and achieve satisfactory results

Reasons to avoid

• More expensive than Epifanes
• Not as impact or abrasion-resistant as some other offerings
• Not as much UV protection as some other offerings

Buy International Schooner Varnish on Amazon (UK)

Buy International Schooner Varnish on Gael Force Marine

Buy Interlux Schooner Varnish on West Marine

Total Boat Lust High Gloss Marine Varnish

Best value boat varnish

In recent years, Total Boat has become very popular offering products comparable—and sometimes superior—to the “big three” of Interlux, Petit, and Epifanes, at a fraction of the cost and their “Lust High Gloss Marine Varnish” is no exception. This one-part formulation uses linseed oil and a modified polyurethane base.

Reasons to buy

• Very affordable one-part proper “marine” varnish
• Does not require sanding
• Comes in matte for those seeking a satin finish
• One-hour re-coat time

Reasons to avoid

• Tends to cure quicker than most varnishes and therefore can cure before properly “flowing out”
• Requires 6-8 coats

Buy Total Boat Lust High Gloss Marine Varnish on Amazon (US)

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Cetol Marine Wood Finish

Best boat varnish for external teak

Cetol has been making alternative wood finishes for a long time. While this product does not have the aesthetic beauty of freshly applied gleaming varnish, it lasts far longer and stands up to UV better than every one-part varnish on this list.

When I had peeling varnish on my 1987 Ericson 38-200 sailboat moored in the tropical Florida Keys, I elected to use Cetol’s “Natural Teak” offering in lieu of varnish and found it incredibly easy to apply and long-lasting, requiring no surface prep to speak up but a quick hand sand and power wash. For outside teak, Cetol cannot be beat.

Reasons to buy

• Incredibly easy to achieve satisfactory results
• Affordable
• Long-lasting even when exposed to UV

Reasons to avoid

• Not as beautiful as real varnish
• Softer and less durable to impact/abrasion compared to most varnishes, especially polyurethane formulations

Buy Cetol Marine Wood Finish on West Marine

Miniwax Helmsman Spar Urethane

The last product featured on our list is Miniwax’s one-part polyurethane spar varnish. While not the most beautiful finish available, this product is durable (hard and abrasion-resistant), easy to use, and very affordable, making it a good choice for touching up one-part varnishes inside a boat’s cabin.

For repairing, touching up, or even redoing cabin soles, this would also be a decent budget option and therefore is included on this list. Unlike the many UV-resistant offerings on this list, Miniwax Helmsman is not very UV-resistant and therefore is not recommended outdoors.

Reasons to buy

• Very affordable, even for a gallon
• One-part polyurethane enhances durability and longevity over alkyd-based products
• Good for sailors on a budget needing to repair and touch up existing interior varnish

Reasons to avoid

• Not as beautiful as alkyd-based marine spar varnished
• Not very UV-resistant
• Yellows in sunlight

Buy Miniwax Helmsman Spar Urethane on Amazon (US)

Hempel Dura Gloss

Best solvent-based boat varnish

Hempel’s Dura Gloss Varnish is a urethane modified alkyd, ideal for interior use

On the downside, alkyd varnishes lack resistance to abrasion and usually only one coat can be applied per day, which can make varnishing a drawn out process.

The more expensive types are formulated to speed up cure times, improve gloss retention and generally last longer.

Buy Hempel’s Dura-Gloss Varnish on Amazon

Which type of boat varnish to choose?

Varnishing often appears to be a simple task, but there’s a bewildering choice of boat varnishes on the market, writes Rupert Holmes.

An understanding of the qualities of different types of varnish is needed to choose the optimum one for each purpose. This is particularly true for exterior woodwork which has to withstand the ravages of sun, rain and frost.

There are only a few basic types of varnish, although in many cases hybrid products are available, particularly alkyd/ tung oil and alkyd/modified urethanes that can offer a wider range of desirable properties.

Polyurethane boat varnish

Polyurethane varnishes are a harder option with good wear resistance, but they lack the flexibility of alkyds. In addition, they tend to sit more on the surface of the timber, so often do not adhere as well to the substrate, which can make them prone to flaking and chipping.

The lack of flexibility makes a pure polyurethane unsuitable for traditionally planked boats, but it can be ideal for plywood, as well as for cold moulded and strip planked hulls.

Polyurethanes are available as both one-pot and two-pot products, the latter giving a harder coating and faster cure, which allows multiple coats to be applied in one day.

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If you need to save the varnish overnight, take a look at this top tip on preserving two-part varnish in the fridge. However, they are a much more expensive option.

N.B. One-pot polyurethane can be applied over two-pot varnish but not the other way round.

Ultra-flexible single-pot polyurethanes, such as Coelan have an elasticity of more than 300%. It can also seal cracks, is highly resistant to impact damage and doesn’t need overcoating for several years and can last twice as long as traditional varnishes.

The biggest downside is that it’s four or five times more expensive than typical basic alkyd varnishes, so up-front costs are higher, although its long term performance means the total cost difference will be smaller.

Tung oil varnish

Tung oil is also frequently used in traditional varnishes: it soaks in well and, although a pure tung oil product will usually cure very slowly, the final finish is very tough.

Solvent-based varnish

Traditional solvent-based one-pot alkyd varnishes are ideal for use with traditionally built wooden boats. The coating is soft but flexible, which makes it resistant to cracking when used on timber that expands when wet and contracts in dry summer weather. Additionally, the initial coats tend to soak into the timber effectively.

Epoxy resin

Epoxy resin can also be used to coat timber, but generally has poor resistance to ultra-violet light, so a varnish needs to be applied over the top. Beware inexpensive ‘yacht’ varnish sold in DIY stores – the low prices are usually easy to explain in terms of extended drying times or poor long-term performance when used outside.

Dealing with surface damage? Don’t delay!

Whatever type of varnish is used, don’t delay on sealing any areas of damage. The key priority is to keep water out, so don’t wait until you have time and suitable weather for a full repair – touch in the damaged area immediately.

This may not have a silky smooth finish initially, but don’t worry. Even if it’s a few weeks before you’re able to do a proper fix you know there won’t be any further degradation.

Top boat varnish tip

A useful tip is to clean out one of the small match pots DIY stores sell to enable customers to test household colour schemes and fill it with varnish. They have a brush built into the lid, which never needs to be cleaned, thus making a quick touch up of damage a task that only takes a couple of minutes.

Find out how to get the best finish with these 8 top tips for varnishing.

Didn’t find what you’re looking for? Head to Amazon’s dedicated boating page for more marine products.