Le Tonkinois -lakkausopas ja käytännön vinkit

Le Tonkinois Marine N°1 -lakalla sivellään puuveneen puuosaa venevajassa.

A steady pace is an advantage when varnishing with Le Tonkinois. Thin coats, a clean brush and sufficient drying achieve more than trying to finish with a few heavy coats. The warm colour of oil varnish and the possibility of local maintenance are reasons why many wooden boat owners return to it year after year.

This guide helps you choose between Marine N°1, traditional Vernis and their preparation treatments.

Marine N°1 or traditional oil varnish?

Product	Purpose	In practice
LeT Marine N°1	Glossy oil varnish for a boat's wooden parts	The manufacturer's marine option, including wooden parts exposed to weather and UV.
LeT Öljylakka / Vernis	Traditional general-purpose varnish for wood and suitable metal	A flexible oil-varnish finish; the application and existing treatment guide the choice.
Bio Impression	Priming bare wood and evening out absorption	Wood primer for Marine N°1; remove excess that has not soaked in.
Gelomat	Adjusting the gloss of the final varnish coat	An additive for varnish, not a protective finish on its own.
LeT Öljypetsi	Colouring wood	Test the colour before treating the entire part; choose the final varnish for the application.

These instructions concern varnished wood above the waterline. The boat's wooden structure, existing finish and location of use determine the whole system. Gloss or familiarity with a brand does not replace checking the substrate.

Practical tips to avoid the most common problems

1. Stir gently; do not shake the tin

Shaking can introduce air bubbles into the varnish. Stir gently according to the packaging instructions. Pour only the amount you need into a working pot and close the main tin. This makes it easier to keep the working varnish clean.

2. Do not load the surface with too much varnish

Dip the brush only far enough to keep application controlled. Work in small areas and check in raking light that varnish has not built up on an edge, in a corner or at the bottom of a vertical surface. A thick application is not necessary for good protection with oil varnish.

3. Finish once, then let the film settle

Keep a wet edge and finish with a light stroke along the grain. Constantly trying to improve a film that is already setting can make it uneven. Try out your technique on scrap wood first; it is easier to use a proven method on the actual boat part.

4. Plan for the entire drying period

Make sure ventilation continues after the working day. A closed space that cools down can slow drying even when it was warm during application. Do not sand nearby while varnish is drying. Outdoors, allow for evening dew and possible rain.

5. A smaller storage container can help preserve an opened tin

On the Merlin Rocket forum, users describe a thin skin forming on opened Le Tonkinois varnish. A practical approach is to reduce the air space above a remainder stored for a long time by transferring it to a smaller, tightly closing container suitable for varnish. Label the container with the product and required warnings. Store cool, dry and protected from frost according to the manufacturer's instructions.

If a skin has already formed, do not stir its pieces into the varnish you will apply. Check that the varnish is usable before starting. Clean the rim before closing: drying varnish around the lid makes a tight seal more difficult.

The Marine N°1 system for bare wood

Check the substrate. The wood must be sound, clean, grease-free and dry. Marine N°1's technical instructions specify a maximum wood moisture content of 15 %.
Sand and remove dust. Do not leave grey, soft or loose material beneath the new varnish.
Prime with Bio Impression. Let the oil penetrate, then spread or remove unabsorbed excess as instructed. Particularly absorbent wood may need several wet-on-wet applications.
Allow the primer to dry. The primer's own drying time and the waiting time for heavily saturated wood are not the same. The Marine N°1 system instructions allow 1–2 days for oil in thoroughly saturated wood.
Apply Marine N°1 thinly. For brush and roller application the product is ready to use: it is not normally thinned.
Wait before recoating. At +20 °C, wait at least approximately one day before the next coat. Apply no more than one coat per day. If the film is not dry, wait longer.
Build a film suitable for the application. The manufacturer recommends 6–10 thin Marine N°1 coats for a boat's exterior, depending on exposure. Apply these over several days with the required drying intervals.

The manufacturer's minimum application temperature is +12 °C. Cold, high humidity, heavy application and poor ventilation slow drying. Surface-dry does not mean cured for service.

Why does varnish wrinkle or craze?

In a YBW discussion about Le Tonkinois, a user described local network-like crazing on a mast and rudder. Recoating too soon, thick coats, sunlight and heat were suggested as possible causes. The thread does not establish a single confirmed cause, but it provides a useful checklist.

Was the previous coat really dry before recoating?
Was the film clearly thicker in a corner or on a horizontal area?
Did the surface become hot in the sun?
Is the damage in the varnish film, or is the wood beneath moving or becoming damp?

Do not cover a soft or wrinkled area with another thick varnish coat. Find the cause, allow the surface to dry, and remove or level the damaged film before repairing it. Repair damaged wood first.

Why do microbubbles appear?

In a Sailboat Owners thread, a user noticed small bubbles in Le Tonkinois Original immediately after lightly tipping off. This concerned that person's tools and working conditions; the account alone does not establish the cause of every bubble.

Try this: stir gently, use a clean suitable brush, apply a thinner film and reduce working of the surface after application. Also check that cleaning product has not been left in the tool or on the substrate. Change one thing at a time on a test piece to see what helps. Continually working a film that is already setting will generally not improve matters.

Intermediate sanding: a clean surface first

Sand out dust nibs, runs and other irregularities before continuing. Make sure the film is dry enough: soft varnish clogging the paper means the surface should not be rushed. Use the grit specified in the chosen product's technical instructions and remove sanding dust thoroughly.

Le Tonkinois instructions from different years describe intermediate sanding somewhat differently. There is therefore no general promise of “never sand between coats”. Your product's current system instructions determine the preparation needed for adhesion; sanding to improve smoothness is a separate matter.

Maintenance varnishing: a local repair may be enough

Boat owners value being able to maintain a sound Le Tonkinois finish before extensive deterioration. A small scratch or worn patch does not always require sanding the entire boat part to bare wood. Clean the area, check the old film's adhesion and make a local repair, feathering its edges before the maintenance coat.

Remove varnish that is extensively flaking or separating from the substrate. Do not assume general compatibility over an unknown alkyd, PU, two-component or epoxy finish: establish the system before starting. Maintaining a proven Le Tonkinois oil-varnish finish is different from switching from another coating.

Where do users' experiences differ?

In the YBW thread, some users praise the finish on a boat's exterior and its local repairability; others find traditional oil varnish soft under heavy wear. There need not be just one “correct” account. A hatch, step, mast and cabin trim face different loads, and Vernis and Marine N°1 are also different products.

Choose a system for high-wear areas according to the manufacturer's intended applications and allow sufficient curing time. Do not judge final scratch resistance immediately after the last coat.

Gelomat: adjust gloss at the end

Build the protective varnish film first. Add Gelomat to the final coat according to the manufacturer's instructions, not to the primer. Make a sample and measure the components consistently for every batch.

Matt: 1 part Gelomat + 1 part varnish.
Satin: 1 part Gelomat + 2 parts varnish.
Semi-gloss: 1 part Gelomat + 3 parts varnish.

Stir the additive thoroughly and gently. Repeating the same ratio helps prevent different gloss levels on adjacent boat parts.

Wood colour and supplies

When colouring wood with LeT Öljypetsi, the wood species, absorption and sanding affect the result. Make a colour sample and coat it with the same varnish as the finished work: a dry stain sample alone does not show the colour of the completed finish.

Marine N°1 and Bio Impression for a bare-wood marine system.
LeT Öljylakka / Vernis according to the application.
Gelomat to adjust the final coat's gloss.
LeT Ohenne for use according to the specific product instructions and for tool cleaning.
Varnish brushes and sanding supplies.

Continue here

Sources and practical experience

Technical content checked on 13 November 2026: the manufacturer's Marine N°1, Impression, Vernis and Gelomat technical data sheets, September 2026 download versions. The manufacturer's frequently asked questions provide additional guidance on selecting applications.

Practical experiences: YBW: local crazing, Sailboat Owners: microbubbles, Merlin Rocket: skinning in an opened tin and YBW: maintenance and wear. The product, age and conditions in each account are assessed separately; these are not confirmed fault diagnoses.

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