White oak finish for outdoors

[Wally Knight]

I'm making new slats out of white oak for some metal benches for a friend of mine. She wants them painted painted black cause she doesn't like the gray tone they turn unfinished. The old slats are black and the paint has almost totally flaked off.
Searches say paint doesn't do well on white oak except for maybe marine paint.
What's the best thing to do for white oak?

[Steve Schoene]

The usual key for exterior finishes is to first use a good exterior primer before you attempt to paint. Also use the best oil based enamel you can find. Marine paint is of exceptionally high quality. I should point out that black can be a difficult color if these will pick up much sun. The black can get quite hot, and that contributes to paint failure.

[Michael MacDonald]

why not a marine varnish so the wood shows. the UV protection will keep them from fading so much...

[Prashun Patel]

The key to maintaining exterior finishes (in my short experience) is maintenance. I have yet to encounter a finish that is one-and-done. Paint is probably the worst offender.

I'm wondering if you can ebonize the wood using a dye or the old acid/metal trick. That, followed by an exterior oil finish reapplied annually?

[Steve Schoene]

Whether a marine varnish makes sense at all depends on how much sun the bench would get. If more than a few hours a day, then marine varnish, even the best of them, such as Epifanes, requires frequent refresher coats (annually in full or nearly full sun) and periodic stripping and refinishing (every 4-6 years or the year after you get too busy to do the refresher coat.

Paint, with pigment, has much greater longevity because the pigment prevents, not just hinders, UV from breaking down the lignin in the wood to which the finish has bonded. Light colored paint works best because it reflects more sun and stays cooler.

[Rob Fisher]

Whether a marine varnish makes sense at all depends on how much sun the bench would get. If more than a few hours a day, then marine varnish, even the best of them, such as Epifanes, requires frequent refresher coats (annually in full or nearly full sun) and periodic stripping and refinishing (every 4-6 years or the year after you get too busy to do the refresher coat.

Paint, with pigment, has much greater longevity because the pigment prevents, not just hinders, UV from breaking down the lignin in the wood to which the finish has bonded. Light colored paint works best because it reflects more sun and stays cooler.

Steve's got it. Light colored paint will work best outdoors. The better the paint the longer the finish will last. Depending upon sun/wind/rain exposure it will need to be refinished every couple of years (maybe 3-7 years?) to maintain the finish.

Rob

[Jeff Beecher]

The key to maintaining exterior finishes (in my short experience) is maintenance. I have yet to encounter a finish that is one-and-done. Paint is probably the worst offender.

I'm wondering if you can ebonize the wood using a dye or the old acid/metal trick. That, followed by an exterior oil finish reapplied annually?

May I ask, What is the "acid metal trick"?

[Prashun Patel]

May I ask, What is the "acid metal trick"?

You soak a 'wad' of steel wool in a 'cupfull' of vinegar for a 'day-or-two'. (all the quotes are bkz I don't find the percentages matter that much).

Then you strain out the steel wool; if you leave it long enough, it'll disintegrate. Paint it on a wood with some tannic acid content and it'll react to turn it grey to black. I've never tested how light-fast this reaction is, though.

[Jason Roehl]

According to a Purdue researcher (he has wooden panels in various places in this county), the longest-lasting exterior finish system on wood is:

1. Freshly sanded wood, but not too fine of a grit--this usually means that the wood gets treated in less than a week, though I prefer almost immediately, since Indiana is sunny and humid in the summer.

2. A clear, penetrating sealer on all sides.

3. A coat of quality, ACRYLIC exterior primer. I now use Glidden's Gripper, as it has stain-blocking properties. Oil-based primers, while good for their stain-blocking, are not very flexible, so wood movement breaks them down in pretty short order.

4. Two coats of a quality, 100%-ACRYLIC coating/paint. In my area, this means spending at least $30/gallon at a dedicated paint store. Avoid the borgs. For me, I find the best bang for the buck is Sherwin-Williams' Resilience (has very early moisture resistance--can be rained on in 2 hours above 50ºF), though I mainly use that in cooler temps, and go for Duration when it's warm outside. For a black acrylic, S-W has an acrylic "All-Surface Enamel" (it also comes in an oil version--avoid that!).

Avoid applying any of these products in direct sunlight, particularly when it's warmer--this causes too-quick drying and prevents proper bonding.

Exterior oil-based paint for most things is obsolete technology. There's just not much research going into it, and hasn't been for years due to all the emissions regulations. Exterior acrylics have come a very long way in the last 15-20 years, and even have made long strides in the last 5 years. They're just not your father's latex paints anymore.

But, hey, it's not like I do this for a living or anything... ;)

(Whoa! 2500th post!)