Latest News: Forums Technical Getting a good varnished finish on ply decking etc

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  • #3746

    I read somewhere that to get a really good varnished finish on a wood deck you should apply epoxy based resin to the bare wood.

    [ Just realised the somewhere was in a post a bit lower down the forum!, but any updates or alternative advice still welcome!]

    I have now reasonably successfully stripped the paint from my wood decks, which I think are probably original and are coming up not too badly under the sander.

    MY query now is what is the recommended procedure for the varnishing process?

    At a boatbuilders i visited, (Winder boats, Keighley, ) they recommended the SP 320 clear epoxy which is UV stable over any of the other epoxy resins that are available, including the SP 106, which is described as general purpose and certainly not UV stable. The problem they said was short shelf life with the 320 version so they didn’t stock it.

    So my questions are;
    1. how many coats of epoxy shall I apply?
    2. can I then varnish on top and is international yacht varnish oK?
    3. are there any alternative ideas?

    PS; had a look at the international sites but the references to products seem to be to ones that are not available in the UK.




    There are several possibilities. The best looking result would definitely be old style linseed oil and turpentine but that wouldn’t be very practical. As a good second manufacturers have created a combination of modern polyurethane varnish and old fashioned linseed oil. The best known brand for this sort of varnish is “Epiphanes”. A third choice would be a pure PU varnish, made by almost all mayor brands.

    However, none of the above is very durable, though very beautiful it does need regular re-varnishing or at least a yearly touch up to keep the protective coating in mint condition. Lately I have discovered the blessings of two pot varnish. It is very durable. Most treated surfaces on our Wayfarers will last for ten years or more. Only the spots where the ropes chaff would need a more regular touch up. The down side is that two pot varnish is a little dull and does not have the showroom shine we like to see on our boats. But a combination of varnishes is very possible. That is why I would choose the following:

    At least two coats of two pot varnish for maximum mechanical protection.
    A few layers of Epiphanes for good looks. Add layers until satisfied with the gloss. Note: on new work you may want to put a few extra layers, see description on the pot.

    The secret of a good coat of varnish is in the preparation, good degreasing , fine sanding and cleaning. And yes, it is hard work but in the end you will be rewarded by a professional showroom shine. Applying the paint is easy, just follow the directions on the pot. It takes only 10% of the time to actually paint, 90% of the time goes in preparations.

    I don’t think there is much difference between brands, in fact most come from only two chemical multinationals (AKZO-NOBEL and DUPONT). Avoid no-name brands often found in the large DIY superstores. Those so called “Yacht paints” are easy recognized by the absence of a description of what is inside the pot. It is my belief that the manufacturers use these El-cheapo brands to dump failed brews. By not telling us exactly what is inside they can put anything in it. Hence the quality may vary between pots. In other words, while your neighbor may have very nice results with a no-name brand, there is no guarantee that you will get similar results. All well known brands have an exact and detailed description of the contents such as “polyurethane varnish” or “polyester” (two pot paint), solvents used and their percentages, etc. It is a bit like beer, the well know quality beers mix their failed brews with good beer until it is drinkable and then sell it cheap as a no-name brand.

    A final tip: visit the web sites of the well known brands. Most offer a booklet for free with loads of information.

    Brands I have used in the past on my W’s: Epiphanes, International, Sikkens, Hempel.


    Using 2-pot varnish years ago (before epoxy finishes became sensible and normal) I applied between 12 and 15 coats! The first one was about mostly thinners, with just a little varnis: that soaked into the wood very quickly and dried in about 30 minutes. The next had a bit more varnish, and so soaked in a little less, the third coat was almost the recommended mix. These are all applied on one day. At that stage, the gain in the wood has risen, so you can rub down again with 800-1000 or so wet and dry and get the surface very smooth. Then 5 or 6 more coats, another rub down, and then the final 5 or 6 coats. The final coat is again VERY thinned (as long as it doesn’t run!!), as this gives the quickest drying, fewest flies, best looking surface.

    But these days, I would go with 2 coats of epoxy and 2 to 3 coats of normal one-pot polyurethane varnish.


    @JordanChris wrote:

    Using 2-pot varnish years ago (before epoxy finishes became sensible and normal) I applied between 12 and 15 coats!

    Never dilute two pot varnish! It may become dull due to solvent enclosure. Also it may get porous if the solvent evaporates and leaves tiny holes. Modern two pot varnishes (epoxy as well as polyester) bond well to wood and there is no need to soak the wood. It will only make the wood heavier and your wallet lighter. All two pot varnishes protect the wood sufficiently after just one layer. A second layer is used just to be sure and it is virtually impossible to get a smooth surface with just one layer. (I am mainly repeating the instructions that are on the pot here).

    Classic varnish is of course a different story. But even then you should be able to get a good thickness of coating in five layers. A varnish that is well adjusted to the brush (or rather the pressure of a brush) should dry without stripes. If you need 15 layers you are sanding too much in between layers or the varnish is not adjusted to the brush, often too much white spirit has been added or a wrong brush is used.

    Varnish (and paints) are tixotropic. That means they get thinner by the movement and pressure of the brush. The effect can be adjusted by adding white spirit. A large brush needs thick, almost syrup like, varnish and a small brush needs thin, more water like, varnish. The trick is to adjust the varnish to the brush in such a way that the brush stripes disappear a few inches behind the brush but before the varnish thickens again, and also it should thicken before it starts to run. Obviously the pressure applied by the person painting plays a role in the process as well. A well adjusted varnish/brush results in layers of maximum thickness without stripes or runners.

    When I apply one pot PU varnish to bare wood I use 50 % white spirit with quick brush strokes (or a quick roll) to avoid deep soaking of the wood. The idea is just to close the pores of the wood with a minimal amount of varnish. The white spirit will evaporate leaving just enough varnish to close the wood pores. Sometimes it takes two coats to fully close the wood pores. Then pure varnish goes on with just enough white spirit added to adjust it to the brush used. PU varnish will stick to most sorts of wood perfectly without the need to soak it. Teak and a few other greasy sorts of wood can’t be varnished in this way, they need some extra preparation but those woods are a problem with all varnishes including two pot varnishes.

    I always aim to use as little white spirit as possible to get my layers as thick as possible. With this technique I seldom need more then five layers to get sufficient coating thickness and a true showroom shine. And also white spirit has a negative effect on the end result. That is another reason to use it with care.

    Thinner (often Toluene or Xylene or a mixture of the two) or Nafta are only for spray painting (or for cleaning our brushes). they have no or very little effect on the tixotropy of the varnish and therefore are unsuitable for brush varnishing.

    If a varnish is not adjusted well a roller will not help, it suffers from the same effects as a brush. When using a roller we also need to find the perfect tixotropy just like with a brush. If you can’t get a perfect finish with a brush a roller does not help and visa versa. whether to use a brush or a roller is op to your personal preference. Some people find it easier to distribute the varnish evenly using a roller. More important is to be quick end firm because the white spirit will evaporate and if we brush or roll too long the tixotropy will change to the point that we cannot get a good result anymore.



    I never realised there was such a huge amount of information and opinion about applying varnish! I was thinking of spraying as well, due to my neighbour being a paint technologist and having a degree in the subject and another friend having some spray gear. (But seriously, I think I will stick to a brush ) and I have now ordered some SP system UV stable epoxy on which I intend to apply a coat or two of varnish to finish

    But thanks to all who have replied and shown interest.

    Graham Smout


    THANKS, Swiebertje

    GREAT to see such a knowledge being shared. I (we) now know so much more than we did before.

    Colin Parkstone

    Lets not forget the place that can ruin all your work on the deck tops, the underside of the decks!!
    If your going too do all this work ,take the time when the boat is upside down to varnish the underside of the decks.
    Use the same varnish as the top so that if it finds its way through to the top decking,and it will, it will match and blend with the deck coating.

    CP 😀


    When (??!!) i get to varnish the newly fitted decks, what quantity of varnish will I need? ie, how much shall I buy? I’ve come across two on line suppliers; the price for SP Ultravar 2000 varies by 100%. Any one have any warning regarding problesm with suppliers?


    I would recommend you go down the SP route, they have a very good system of 3 coatings for your needs. If you call them I’m sure they will be more than happy to give you application information. From my experience I would opt for the following:

    2 coats of Eposeal 300, this is like water and will soak deep into the ply.
    3 coats SP320, the 2nd and 3rd coat can be applied before full curing to save time on rubbing down. This will fill the grain up and give maximum protection.
    2-3 coats of SP2000 ultravar for the UV protection.

    When putting all of these products together you need to adhere to their instructions carefully, the eposeal and the SP2000 are solvent based and the 320 is solvent free, therefore after you have applied the eposeal you need to make sure that all of the solvent has evaporated (usually about 60hrs in a warm environment).
    After putting the 320 on you should wet n dry sand the waxy top off and let it dry for about 24hrs then apply the SP2000, again multiple coats can be applied without sanding, however it is best to sand down before the last coat to get the best finish.
    As with any information like this it is always best to check the manufacturers instructions in full before purchasing.

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