priming woodwork

I read that the proper sequence for painting wood is:- primer, undercoat, topcoat. This is at least one more layer than I customarily apply ( to whit, the primer ). If I need primer, how does varnish cope without having one? Undercoat I understand in certain circumstances, as it seems to stick tenaciously to wood, and provides a consistent/sandable surface that the topcoat can sit on. Anyone out there know if I also need primer to get a decent result on repainting some old exterior pine which I have stripped and sanded? I want this to last a long time so will use primer if that gives me some kind of advantage.
Andy.
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If you're putting the timber outside again and want to keep the natural look of the pine, then give is a few coats of hot bees wax.
http://www.huddsonline.co.uk/household_and_diy_waxingoiling_wood.htm
But if you are going to paint, and you want the longest lasting solution, then this technique is best.
http://www.antifouling.com/uk/boat_painting_guide/bpg2001/boaters_guides/pages/p62_63_64_65.htm
(watch out for line wrap on the links)
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Sorry !!! Missed one:
http://www.canfixit.co.uk/feature/wood/exterior%20wood%20finishing/exwoodfinishing.htm
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BigWallop

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Mark B wrote:

Well strike me pink. Only primer undercoat and topcoat...
First, take yer wood. Its grainy knotty and full of noxious resins. You seal that off with knotting compound, or some other hard clear and turpentine proof layer. If you want mechanical strength you might even apply an epoxy glass layer, or sometimes just paper pasted on will do :-) This covers proes and provides a tough outer surface.
Then you need to get rid of the grain. That's lots of rubbing down, and something like sanding sealer maybe. When you have wood with the surface finish of polished glass, rough it up and put on the primer. One rub with that shows how wrong you were about the real flatness of the surface, as the wood grain shows through.
After about 30 coats of primer rubbed down each time you finally discover flatness has been achieved.
Now its time to think surface finish. If you are using flat paint, well then you can indeed slap that on, but gloss is a problem as it cannot carry much pigment and still look glossy, so slap on the undercoat that has most of the pigment in it. Now sand out all the brush/spray marks and runs.
.....
....
Oh. Yes Now paint it with the gloss topcoat, very carefully with a fine brush, or spray it.
You will have a piece of wood that looks like it came out of a luxury car showroom.
It will be indistuinguishable from metal, or plastic in appearance.
TNP, many days into sanding, filling, and priming a 28" span Mescherschmitt ME 109...:(

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I've recently discovered Crown Solo, so that's the undercoat bypassed.
mark b
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It doesn't. Varnish needs replacing at about 3 times the rate of properly done paint.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Further research on my part suggests that primer is ( as was suggested ) to seal the wood and prevent topcoats sinking in. Anyway, I managed to find a combined primer/undercoat paint so making life simpler.
It may be of interest that my research suggests that for exterior wood, the best paint topcoat, in terms of durability and resistance to flaking, is a water-based pure acrylic type, in gloss or satin. As preparing and painting exterior wood up a ladder is only slightly preferable to sticking pins in one's eyes, I thought I'd share this info.
Thanks for the replies,
Andy
London SW 12

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I use aluminium primer a lot but you do have to make sure the surface is clean - if in doubt wash down with sugar soap and wait till bone dry. Also you do have to follow on with the undercoat very quickly - next few days, or the primer will want washing down with sugar soap to get the undercoat to stick. I carry on applying undercoat - 2 or 3 coats, rubbing down lightly between coats until a perfect covering is obtained, and only then apply top coat - using it as a finishing 'varnish' on an allready perfect surface. A good paint job lasts years - 10 or more whereas varnish needs doing every year if you want to keep it perfect.
cheers
Jacob
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