penetrating primer ?

[Ether Jones]

Last summer I removed the treads from my exposed porch stairs, scraped and wire-brushed them down to bare wood, let them dry in the sun for several days, then painted them with an oil-based primer, and when that cured, I applied a topcoat of latex labelled for use on exterior porch horizontal surfaces.

Already this year, the paint (and primer) is flaking off in large chunks. These stairs are exposed to sun and rain.

When I was applying the primer, I noticed that it was very "sticky", almost like glue. At the time, I thought "man this stuff is great; it's never gonna come off".

Now I'm wondering if perhaps a primer should instead be very thin, like a stain, so that it soaks into the wood and gets a good toehold, and provides a suitable chemical surface for tenacious adhesion of the topcoat.

Is there such a product? Need brand name and product name.

[Norminn]

If the wood was weathered, it should have been sanded down to new wood. Did you use shellac-based primer? Dries fast.

[Ether Jones]

I'm looking for a penetrating primer - one that will soak into the wood like a deck stain does... not just lay on the surface. Does such a thing even exist?

[Banty]

Possibly not - if a primer is formulated to bind to the surface and make a paintable surface, the need for that quality would prevent creating a formulation that would allow penetration as well. In order to penetrate, it can't be stopped on its way by binding to what its passing.

I'm not a paint expert, but I'm a materials engineer, and this strikes me as be one of those kind of problems which have an inherent tradeoff. But I may be wrong...

Banty

[Norminn]

Any good primer should adhere if the surface is prepped right. Failure of the paint is easier outdoors, of course, and all surfaces of the wood need to be covered in order to slow that down, including ends and underside. Might be time to replace the wood and paint it properly before installing it. Easier said than done :o)

The "sticky" primer stumps me - I've used alkyd, water-based and shellac-based - the only one that approaches sticky was the shellac based, because it dries faster and brushing too much could make it seem sticky. You can thin a primer, according to the amount stated on the label, but most are better not thinned. Was yours an old batch?

Outdoors, wood that isn't finished on all sides can absorb moisture through the end grain fastest, and through the underside. The moisture then makes the paint loosen. Oil primer is probably more compatible with raw wood because wood always has a bit of oil in it, some more than others (redwood, cedar).

[Tom The Great]

Is it possble, that the wood isn't up to grade for painting?

I have some boards on my deck that unless completely sealed top and bottom, they swell and contract and oil based sealants still flake off on NON-traffic surfaces in two years.

later,

tom @

[NickySantoro]

Two things... I suspect there was some contamination it that original primer. Do you recall the brand? This product has served me well. All the majors make an equivalent. Benjamin Moore Fresh Start® Moorwhite® Penetrating Alkyd Primer 100 FWIW YMMV

[RicodJour]

Paint is not a single material, it is a solution. The solvent does the penetrating and the resins and pigments impart the film coating's durability and color. The oil in the oil-based primer does penetrate the wood. Water-based coatings will also penetrate, but the depth of penetration with either oil or water-based is not very deep at all. Probably 1/16" or so, maybe even less.

Many primers are described by their manufacturer's as penetrating primers. I suspect that either the OP's paint was old/bad, as I've never heard of a sticky oil paint right out of the can, or that the wood wasn't fully dried/prepared.

R

[Nospam]

Moisture will seep into the treads from anywhere exposed opening no matter how small (such as where the treads are nailed). Once water get into the treads, the sun will then bake the treads forcing the moisture to the surface, and thereby cracking/blistering/peeling the paint (including primer).

Robert

[Ether Jones]

The "toner" deck stain I use on my deck soaks very deeply into the wood and does not peel, even though I treat only the exposed side of the wood. My deck is a southern exposure and gets merciless sun and rain and snow, and high foot traffic.

So I guess what I'm looking for (for my painted porch steps) is a primer that soaks in like that, AND provides a chemically suitable surface for tenacious topcoat bonding.

It wasn't my idea to paint the porch. The previous owners painted it. It is a large wrap-around so there's no way I'm gonna strip the whole thing or replace all the boards. I'm pretty much stuck with paint.

The unexposed low-traffic areas are doing fine; it's just the breezeway area (which gets lots of rain and foot traffic) and the three sets of exposed steps (which get sun, rain, and heavy foot traffic) that won't hold the paint.

[RicodJour]

Stain doesn't peel. It wears/washes away. You could use a solid body stain on your porch, but you'd still have lots of preparation to do.

R

[Ether Jones]

It is my understanding that clear stain, toner, and semi-transparent generally do not peel. But solid-color stains DO peel. Just search alt.home.repair for posts containing the words "deck" and "stain" and "peel".