Paint coming off, what caused it?

[thudpucker]

Confronting failure's post reminded me of some Old boats I've owned.
A 53 Chris Craft, an old Cedar boat, old plywood, other old planked boats.
Some houses I've seen as well.
All had the same characteristics.

The paint is separated from the wood, leaving a nice well sanded finish with a thin chalky light colored coating of some kind.

The old CC had been painted a dozen times or so. Roughly knocked off the curling paint and repainted on top whatever was there. Thats fine. From 30' or so it looked great. I'm not holding anybody's feet to the fire over trying to make an old Hangnail look like a new effort.

It's the thought that my next paint job on a new piece of wood might look like that in a couple years is just killing me.
I'm actually scared to try anything for fear of getting it wrong the first time and not being able to fix over the end result.

This is going on a little Jon boat. Plywood for the most part. Porch n' Deck paint.
I wonder if treating the whole works in Wood Oil might be a better start than just primer and paint?
What'll make it stick so well that no part of it will ever peel?

[alan white]

Just prime and paint. Use alkyd primer and paint. Paint lets go because moisture gets between paint and wood. A lot of times the other side of the wood isn't properly sealed.
Make sure the wood is dry and clean before priming. Any cracks or scrapes allow moisture to enter and migrate behind sound paint. Seal all scratches and points of water ingress as soon as they appear.

[thudpucker]

Thanks Alan, that sure simplifies things.

Did they have the Alkyd primers back in the 50's?

Or more pertinent, what did they use for primers back then?

Would it be helpful to soak the wood with Wood Oil to help the Alkyd primer sink in further?

[PAR]

Alkyds are all they had in the 1950's No, contaminating the surface with oil wouldn't be particularly helpful, unless you can insure it's raw, unsealed wood, in which case I would use a 50/50 mixture of turpentine and linseed oil, with a few ounces per gallon of Japan drier to expedite the drying time. This isn't necessary for a good alkyd primer, but some find it reassuring for some reason.

[thudpucker]

Good explanation PAR. Thanks a bunch.

[Petros]

paint continues to cure over long periods of time, becoming harder and more brittle. The older formulations tended to shrink as well, the combination causes cracks in the surface that would allow moisture below the surface, allowing the wood to swell, compounding the problem.

One way to prevent the moisture penetration is to put new coats of paint over the old. Eventually the build-up will start cracking and falling off after many years of repainting. That when it is time to strip it off (heat gun works best) and starting over with fresh paint directly on the wood surface.