Painting question

[Random]

I'm currently rebuilding some 80 year old windows on my glassed in porch. This involves stripping the paint and replacing most of the window putty, which was badly deteriorated. I did half the windows last year and am in the final stages of the remaining half.

Of course, as the windows were stripped to the bare wood, I'm starting with a primer. Last year, I used a water based (latex) primer and finish coats. Both were rated for exterior use. Because I was disappointed with its durability, especially where the windows came in contact with the frame, I decided to use oil based paint on this year's windows.

I had no problem finding an oil based primer, and it seems to be solidly adhering, although it is obviously too early to judge its durability. I'm now ready for the finish coat, but the well-stocked home improvement store I tried had little in the way of suitable oil based paints, except for primers.

Was this a fluke, or does everybody use latex paints these days, except for primers? Also, any tips for improving durabilty when painting windows, which by their nature are removed and reinstalled every year, which leads to wear where they touch the frame?

[Inky-]

Oil based paints are pretty much out of favor these days for a lot of reasons.

(1) Speed of drying.
Oil based paints don't so much "dry" as oxidize, that is to say bond with oxygen to form a simple polymer. This process, depending on the pigment added, can take from days to months. So, in order to make the paint dry faster either chemical dryers are added (cobalt siccative, mostly) or the oil can be boiled and mixed with solvents. Both options are stinky and toxic, and lead to the problem of...

(2) Durability
Drying oils, especially chemically treated mass-produced commercial grade flax/linseed oil, gets more and more brittle with age. Oil films expand and contract more with temperature changes than latex or acrylic films and are also more prone to microbial and fungal rot.

(3) Changing your mind
One of the biggest problems with oil-based paints is that once you start using oil paint on a wall, furniture, windowsill, etc. you can't go back to using latex paints on it. Even after being dry for years an oil painted surface can be too smooth and non-porus to accept a coat of acrylic without sanding.

So, thats why oils have fallen out of favor.

[pluto]

I think you're a victim of our easy cleanup era. Your average homeowner isn't going to take the time to clean his painting equipment with mineral spirits when he can wash them up with soap and water.

Just a guess, but the fact that you could find the primer but not the paint makes me think there's not much difference in performance between oil- and latex-based paints. It makes sense that primers would differ, since one of the main features of primer is penetration, but for paint the main features are coverage and durability, which (I'm guessing) are about the same for oil or latex. If not, there would be painting contractors out there offering a premium service, using oil-based paint, to their customers who are more concerned with a long-lasting, quality paint job even if it costs a little more.

OTOH, you might try a paint warehouse rather than your local home hardware store. They might have some specialty brands for fussy people such as yourself. But it sounds like it's going to cost a little more.

[Inky-]

Oh! Forgot to mention why oil-based primers are still around.

Some woods (pine mostly) will bend and warp when exposed to even the relativly small amount of moisture from a coat of water-based paint. So an oil primer is used to seal the grain. Primers (like gesso) are usually mixed with something porous like talc or titanium dioxide to give an abrasive "Tooth" that will take later coats of acrylic paint.

[Random]

Thanks. That makes sense. I'll stick with the latex finish coat.