Boats have been varnished in one way or another for hundreds of years and yet despite all that time and practice, it appears that there is still no agreement about what's the best stuff to use. Every year there seems to be some newer or better varnish available but despite that some old boys are still varnishing boats with finishes that look like glass using just the most basic and old-fashioned varnishes.
This is a quick overview of just some of the clear-coating varnishes that I know about and that I have used in the last few years.
Basically they all fall into two kinds, modern hard varnishes and traditional supple ones. If the boat moves (plank on plank….not through the water!) by which I mean any old clinker or carvel boat then you really have to use traditional varnishes, but if the wood is stable, as in most glued and moulded boats then you can use either traditional or modern varnishes.
The other thing to consider is that sooner or later you will want to remove the varnish, how ever well it was originally applied. Believe me, removing polyurethanes is about as hard as getting the knickers off a jehova's witness on your first date, whereas removing traditional varnish is as hard as….at which point maybe I should drop this rather dubious metaphor.
Traditional Marine Varnishes
These are the traditional one-pack varnishes. As a general rule they fall
into two types, the standard varnishes (made mainly of alkyd) like International
'Original', Blakes 'Classic No 1' and some other cheaper varnishes like
MBM 'Prima' which I rather like.
Then there are the Premium Traditional Marine Varnishes like International
'Deluxe', Joton 'Ravilak' from Norway and the best Varnish in the World,
the Dutch 'Epifanes'. These varnishes tend to have a higher tung-oil content,
be darker in colour and are certainly more expensive. They are not difficult
to use and certainly have 'good body' as they say (they not me....what
kind of anorak do you think I am).
Mono-Urethanes & Single Pack Poly-urethanes
There are quite a few of these, (International 'Schooner' & Epifanes
'Mono-urethane' are two) however the only one that I have really used
much is the Blakes 'Single Pack Polyurethane' and that's just great! Quite
a few of them (including the Blakes single pack) are based on cyano-acrylates
(like SuperGlue - which is why they are so hard) and use the moisture
in the wood to cure them. I am a real fan. It sets like rock (so you can
polish it - which you can't do easily with traditional varnishes), dries
quickly, is not particularly temperature dependant not too hard to get
off again (but no where near as easy as the trad varnishes) and although
harder to apply than the traditional varnishes, is quite easy if you follow
my 'Idiots guide to Varnishing'.
Twin-pack Polyurethane.
Mmmmmmmm, I do not deny that there are some boats out there that are varnished
with twin-pack Poly-urethanes....and that they look gorgeous.....and I
know that they will last twice as long and all that.....But I am afraid
I just can't bring myself to recommend them, well at least not for a 'classic'
boat. So why? Well the problem is that they are so strong, you can never
get them off again, well not without destroying the wood underneath. A
heavily worn area of mahogany would be OK, but your chances of getting
it off your thirty year old ply deck without destroying it is not high
at all. It also just does not look right to me.....I can't really explain
why, you can certainly get a wonderful glass like finish, but it somehow
looks like solid Perspex rather than giving that golden depth you see
when you look down into your pint of Bass, with the evening light refracting
through....ah now I am getting all romantic....the thought of a few coats
of Epifanes does that for me....sad case I know. Oh, and did I mention
that they are next to impossible to apply well. Well that's a bit unfair,
you can do it if you can get all your work into a confined and controlled
space. A friend had 3 attempts with one make of very expensive and very
swish varnish, until in the end in total exasperation he rang up the suppliers
who informed him that all his problems were down to him applying the varnish
in a too cold and too humid an atmosphere......so he wrote down the recommended
temp and humidity and then made a quick call to the Met office.....yup
you guessed it...the Met office reckoned that on average they would not
expect more that 5-6 days a year with those conditions.......mmmmmmmm....I
normally varnish outside, so you can see that twin-packs are not really
quite the thing for me.
Epoxy Coatings
Really these are just the same as the Two-pack poly-urethanes. Everything
I said about them is also true of Epoxy varnishes. They are just as hard
to work with.....maybe worse, although I have worked with these quite
a bit (even outside at times, not that the results were anything to be
proud of). They are very prone to going white if you work too late in
the day and the due comes down a bit early. Any rain is guaranteed to
totally ruin your finish and if it all goes wrong and you have to sand
it off........then get ready to take a whole day out of your schedule....it's
hard....and it takes forever. At least it's marginally easier to totally
remove, although this depends on the make of epoxy. Epoxy is easily softened
with just a little heat. I have used one make of epoxy varnish (SP.....if
you really want to know) that on a real hot day actually melted under
the covers and stuck to the cover in long strips when it was pulled off.
Hey, at least it was easy to get off with the hot-air gun! Makes you think
though, painting your carbon spars in white might not be such a bad idea!!
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Remember epoxy does not like getting wet before it really hardens.....leave it too late in the day, and it all goes 'orrible |
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And I do mean horrible, so when it is this bad, you are just going to have to sand it right back and start again...don't panic, it can easily happen....it wont effect the final result, but it will take you a bit of effort to get it back in order |
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Wood Stains
Now for me, when I think of a wood stain, I think of the spirit based
dyes that we use to put back in a bit of colour into our faded decks when
they have seen just a bit to much summer sunlight (without enough varnish)....but
for some Wood stains are a complete coating system......and there are
those that swear that these systems like the Dutch Sikkens Cetol system
provide a better level of UV protection, for longer and cheaper than any
other system, after all they are designed for coating exterior wood on
houses, where they guarantee many years protection against all UV. They
might be right....although these coating systems are still alkyd based,
they have quite the highest solid content of any system I have considered
here, which means that they need less coats and indeed should provide
a higher UV protection, which is I admit is the really important thing.
But then, I havn't used these....considered it....been and looked at the
cans...but always chickened out. I know people who have used them, and
it seems that for large areas (big boat hulls etc) it can be real good,
but I do know people who have used them on smaller areas, more under close
inspection who have been less than happy. One of the problems is that
the sheer level of solids makes them less than completely clear, in fact
(well they are stains!) they have a coloured base (in various wood colours).
When this colour is even, there should not be too much problem, but sometimes
you can see the streaks of colour in the stain.....and this can be very
ugly indeed.
Wood Oils
These finishes (Deks Olya and International Dex 1&2 are typical, but
there are others favoured by some boat-builders) were mainly developed
by the Scandihooligans and are really good for boats that are going to
spend a lot of time getting wet and living in wet conditions. O.K. I will
admit it up front, I have never used any of these, so please take any
of my thoughts with a big pinch of salt! Mind you I will give them a go
when I have the right boat. I have been very impressed with the results
that I have seen on some mates boats. They normally come in two parts,
the first is a penetrating oil that sinks right into the wood and becomes
a natural barrier that actually makes the wood itself waterproof. This
first layer, never really sets or goes hard which is what makes it remain
such a good water repellent. Some oil finishes leave it at that, but it's
pretty horrible without the second layer on top. This layer makes a chemical
bond with the soft layer in the wood but provides a surface that you can
build up to a little depth on, to provide a bit of a shine. However it
is still pretty soft and is not really able to provide the kind of depth
of surface that we expect from the traditional varnishes. Of course it
is this softness which is both annoying, but also what makes it so effective
at moving with the wood, never cracking and just goes on keeping the water
out, which after all is what it is supposed to be doing.
Misc Varnishes and other stuff
There are some strange ones too, like a few water-based varnishes. Blakes
have one called SeaTech. Fraid I havn't used it….so I can't really
pass comment, but I like the idea of a water based system. Burgess Marine
also do one called Hydrosoll. It is part of a complete system of water-based
wood seals made by the original inventor of Hammerite. As I said, I am
not mad on wood stains, rather than varnishes, but it does sound like
an interesting system and I must get around to trying it sometime. You
can see more at: http://www.woodsealer.co.uk/
Another thing I have tried….and others claim give that perfect finish it to use a wet-edge extender, these are additives that you add to the paint to make them take longer to dry, which gives them more time to flow out and level out to a perfect finish. The one I have used is called Owatrol, it does do what is says on the tin……I mean it does take longer to dry, and does flow out better, but this is a mixed blessing, it also means there is longer for it to catch dust, longer for it to run and really slows down your varnishing or painting. If you have a perfect place to work and you want to just apply one thick coat, rather than two thinner ones, it can help…..but personally I don't use it anymore as I reckon you can thin the paint, extend the wet edge, apply two coats and do all that in the same time as one coat of Owatrol improved varnish takes to dry. It can also be useful if you have to paint in the middle of a summers day when its got a bit hot…..but I reckon you still need to add a little thinners as well.
Primers
Or what do you put down on the wood under the varnish.
Any primer, clear or coloured has the same purpose, to make a decent bond between the wood and the coating system above it.
Traditionally the easiest way to do this (and of course in those days, there wern't any clear primers) was to use a thinned varnish that was supposed to sink into the wood.....OK that's the theory, but let me ask you something....when you took off the old varnish...did you see any evidence of the old varnish sinking into the wood? No.....you didn't .....and No varnish (or primer) however thinned sinks any measurable distance into your wood.....sorry....but the primer is just trying to make a good bond to the outer layer of the wood. Now I admit that thinning your varnish most probably does make it a bit better at that.
But that was the traditional way, and although I would still do this for a real vintage boat (like my old Merlin) for anything else I would use one of the much better and harder 'clear primers'. These will provide you with a much more secure bond between the wood and the coating system and I heartily recommend their use.
I am aware of two clear primers: International Paints Universal Clear Primer (UCP) and Blakes 'Woodseal' . I think they are pretty similar. Both are expensive with UCP a little dearer. If forced I would say I think that UCP is a teansy weansy bit better.....but I don't think there is much in it and since I use lots of the Blakes Single Pack Polyurethane....I normally use the Blakes Woodseal too. They are both really hard, but I just slightly suspect that UCP makes a better bond to the wood.....although I would be the first to admit that I have absolutely no proof of this and mainly use the Blakes stuff anyway....which is just fine.
Applying them is just identical to applying the varnish on top, just remember that the stuff is HARD! Do make sure that if it is going to need sanding, you do it quite soon before it really cures too hard. Also remember that once it goes hard, it can be difficult to get the next coat to adhere properly. So if you let it go beyond the recommended coating times you will need to really sand it well before putting another coat on. All in all, I would always recommend that you try and put on the next coat just as soon as the previous coat has been through primary hardening (within the over-coating times).
How many coats? this will depend on the flatness and preparation of the wood you are coating. But you certainly need 2 coats. One to seal the wood, then once sanded flat again, another too seal all the exposed wood. Personally I think it is best to keep applying primer followed by sanding until you have got the surface as nice and flat. If you are still substantially sanding between coats, then keep using the primer, until it is really flat.
So that is the primer, what varnish do you put on it. Well any of the
varnishes, either two-pack, single-pack, or conventional will happily
go on top of either of these primers. I often happily work with a clear
primer to get a good flat base and then totally finish off with traditional
varnish. No probs!