What goes on the wood first? Sealer/primer

At one time in my youth, I was so entirely too tired of scraping and sanding the old paint off wood boats.
I'd made up my mind to get some kind of Chemical that would penetrate the Softer parts of the Wood and also the Grain or Hard parts.
I wanted .030-.060 thousandths of an inch penetration. I didn't want any peeling or scalloping again ever!
So in a few years, a light sanding and a second coat would be all that was needed.

So I'm not a Chemist, and never persued that dream.

CPES sounded like the right way to go in 95 so I used some of that on two boats. Somehow the boats both got away so I dont know the end of the story. It was certainly good to work with though. I liked it.

Some body on this forum was saying CPES is not water proof.
I took that to mean it might not hold paint or primer or some such.

Fine! I'll just use the normal Paint method and burn the boat in a few years.

The Painting Question is: What goes on first, then what, and then what?

I lean toward Porch n' Deck Paint for the final coat. This is a cheap little Jon boat or a Pram. I still havent decided. But it's gonna be inside the barn most of its life. Hot and humid here, but not much direct sunlight.

 

The process should be. Encapsulate the wood in epoxy, build the boat, then a layer of glass and epoxy, then paint.

Basically epoxy will waterproof anything, but isn't UV stable.

 

I'm not arguing with you, but I never thought that was a good idea.
I was working with old wood boats long before Epoxy and F/Glass became popular.
I got some free Samples from a Paint shop in Seattle and tried it out on a Cedar boat.
I'll stick to paint.

 

CPES and other penetrating epoxies aren't water proof (not even close). In fact, many of the really good paints resist moisture vapor ingress better. Back in the 90's, it was thought the "way to go" but since, the jury has come in and it's usefulness has been shrinking in scope for many years now. Most progressive professionals don't even find a need for the stuff any more, though admittedly there are some occasions it's a reasonable product.

The decision to use epoxy, should come with a small ball peen hammer, to speed up the process. You give yourself a swat in the temple with the ball peen, then say "encapsulation". If you do this sufficiently enough before you purchase the epoxy, you might callous yourself up enough, to prepare yourself for the result of the decision to use epoxy.

By this I mean epoxy does several things, but when it comes to using it as a wood coating, you've crossed over a line that most don't realize initially. This line can be a huge, fat, goo filled beast and this is the point. For epoxy to effectively seal wood, it must stabilize the moisture content. To do this you have to have sufficient uninterrupted film thickness on everything: inside screw holes, particular attention to end grain, the whole 9 yards, which for most is way over the top, as to what they thought they were in for, when they made the encapsulation decision (hence the ball peen suggestion).

Some forms of boat construction just have to incorporate encapsulation. It's the nature of these types of builds, but not all builds require this and the boat will not die immediately upon toughing the water, if it's not encapsulated.

If you have a traditional plank on frame (plywood over frame included) build, then you probably don't need encapsulation. This doesn't mean you couldn't benefit from encapsulation, because you probably could, it just means you could live without it and your temples will be grateful.

The short answer to your question is seal it first, then paint. Now the real question is, what to use as a sealer. Well, a true sealer controls moisture content and the the best at this is epoxy (pull out the ball peen), but a few coats of a quality primer, followed by top coats works too, though it doesn't seal nearly as well as the ball peen method.

When I work on raw wood projects, I use thinned primer for the first coat. I cut it about 15% to 20% and let it "flash off" good, before the next coats go on. This lets the primer get a good "grab" on the wood fibers, so that subsequent primer coats have a nice bond. I also use a fair bit of primer, usually 4 coats. You see, if you sand between coats, you'll actual knock off one of the previous coats in areas, so I insure there's plenty of primer in place before top coating. Only the very first primer coat is thinned. No other thinning is required, because once the first primer coat is dry, the wood is effectively sealed. The only "thinning" I might do is to get good "flow" from a top coat and this is usually quite a small percentage, depending on environmental conditions mostly or if it's being sprayed.

 

Thanks PAR.
What do you thin the primer with?

In paint, do you get the Reccomended primer and Under Coat to go along with the outer coat?
I think my Outer coat is going to be Oil based Porch n' Deck.
Sombody also mentioned Latex out side paint. Any comment on that Latex stuff?

 

I have always used the paint system advised by the manufacturer, however some use oil based topcoat highly thinned for undercoat and gradually reducing the amount of thinners until full strength. This requires lots of sanding and painting but apparently works well.

A professional boatbuilder mentioned using "yard paint" which was all the oil based topcoats, undercoats, thinners and primers left over from various jobs and emptied into a 44 gallon drum. Worked well as a primer undercoat apparently!

 

"Yard Paint" reminds me of a big Garage I built. 22X52' and 12' Tall.
My neigbor said he could paint that in an hour if I'd do the holding a move the ladders for him.
OK to that, hey! What colors is gonna be? I asked. He said: "I dont know, something dark he thought!"
Ok, we did it from his 'yard barrell' and it was a dusky dark blue. Worked good and lasted a long time too.

I have some Brown in the barn, but I dont want any brown boat.

 

Lighter colours last much longer in a boat. This is especially noticeable over epoxy/glass, as dark colours encourage 'print through' of the glass fibres.

 

really no such thing as a penetrating epoxy. Such products are just solvent thinned epoxies. They penetrate no more than the raw solvent would by itself. And when the rot it 'wet or damp' they don't drive out the water or make it disappear. At most they form a crust over it. Note that all 'penetrating epoxy tests' are done using sawdust etc where any liquid will 'soak in' an impressive amount.

there is a web site on penetrating epoxies. www.epoxyproducts.com/penetrating4u.html

 

Here's a Basic question.
What's the funtional difference between a "Sealer" and a "Primer"?
They sound the same to me. Something a bit thinner that will penetrate, and yet has a Catlyist that will bond to the Paint.

 

I've never used a "penetrating epoxy".

I just finished painting prefabbed parts for my new flybridge. On plywood panels I do the same procedure every time.

1. Sand and prep plywood.

2. Apply 2 coats of System Three Clear Coat resin. This is a 100% solids clear very thin resin that does indeed soak into the outer ply of the wood. It doesn't soak into mahogany or any of the hardwoods that I've used so I only use it on plywood.

3. Apply fiberglass cloth if necessary, otherwise apply a coat of System Three general purpose epoxy.

4. Fill weave of glass cloth with second coat of resin or, if not using glass cloth sand the initial coat of general purpose resin and apply a second coat.

5. Take a break before painting!

6. 2 coats Interlux Epoxy Primecoat. Follow mfg. instructions to the letter.

7. 2 coats Finish Paint (I like Perfection) and again follow manufacturers instructions to the letter. I just apply it with a good foam roller and don't tip. With the lighter colors this seems to work out fine as they self level very well.

The photos show how this works out.

I like the Clear Coat epoxy because it does indeed seal the ply. This seal may or may not make any difference with regard to preservation of the wood but I do know that it cuts my sanding time down considerably. The subsequent coats of general purpose epoxy don't absorb into the ply and therefore I can use less general purpose resin and sand less as a result.

It's just smoother.

Regards,

MIA

 

difference between sealer and primer (at least for me) is that primers have different allowed VOC requirements. So calling a product a primer or calling it a sealer could legally affect where and how the product can be sold.

 

Good answer Paul.
Later I'll go to a Paint Factory site and get a more difinitave answer.
I do hope that someday I'll start building my Boat and will still have all this info on a CD somewhere.

 

A bit of a sidetrack here...

I once did some work on a World War I era house, that was situated between Glendale and Hollywood (California). According to the family who had owned it from day one, all the interior plaster walls were originally covered with five coats of oil-based paint: a primer coat; two thirds primer and one third finish coat; one third primer and two thirds finish coat; and two finish coats.

They wanted the same thing done on the additions and alterations I contracted for. I'll admit the original paint job had held up admirably, but I had to give them a few reality checks. Today's paints are a lot better than the paints used in 1916; the relative cost of labor vs. materials has swung drastically since then; and blind 'authenticity' has its price.

A five-coat paint job, properly done, would have cost them more than the rest of the work put together.

 

The difference between a topcoat and primer paint is typically silica, spheres or other material. Primer has filler added, plus a higher concentration of pigments to block previous colors. Primers often have less vehicle and more solids, which is why they cover well, can be sanded smooth and seem "gritty" to the touch when dry.

A primer and sealer are essentially the same thing, except in application, unless you're using encapsulation techniques, which takes sealing to a whole different level. A primer can be used as a sealer and a sealer can be used as a primer (assuming not compatibility issues).

VOC content has little to do with what a product is called. Solids content and solids to vehicle ratio are much more important considerations then VOC's.