aggressively thinning latex paint?

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Ether Jones wrote:

just paint the fucking board and stop fuckin around
you coulda been done by now damn nickel holding up a dollar
you sure don't ask for much for nothing do you
you're a real pill
"it puts the brush into the paint and paints the board"
"PAINT THE FUCKING BOARD"
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yeeha wrote:

I didn't want to be the first to use the "f" word, but, yeah. :o)
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wrote:

For your situation the most effective procedure is to use a slow drying oil based primer thinned slightly, allowing it to dry thoroughly, then topcoating with the finish of choice.
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NickySantoro wrote:

Can you recommend a specific brand and model of primer, which is explicitly rated for exterior wood floor and steps?
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You should be using Decking products, following instructions and not making up your own with the wrong product. Your past failures might be the wrong product, prep or aplication on a hot or damp surface. Get and use products designed for the job and do what they say.
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That may work for some here, but others insist that a person totally understand and comprehend what the paint is doing, why, and all the ingredients of said paint.
IOW, they do more thinking than painting.
Steve
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m Ransley wrote:

Most decking products are stains, not paint. Unfortunately, I'm constrained to use paint since the former owner painted the entire porch and I want it to match. Only the breezeway area (about 150 square feet) and steps need refinishing.
Two years ago, I essentially followed the advice you recommended above. The result was unsuccessful, despite scrupulously following the label instructions. I think I posted the details elsewhere in this thread. The paint started to fail after one year. I still don't know why for sure, although many here have suggested possible reasons, and the oil primer seems to be the likely culprit, even though "latex over oil primer" is the conventional wisdom.
Some folks say "paint all six sides", others say "no, leave the underside unpainted so the wood can breathe". I tried both ways and they both failed (six sides on the steps, only the top in the breezeway area).
Some folks say "use oil", others say "no, oil is too brittle and moisture-impermeable and will crack and separate from the wood as the wood expands and contracts due to moisture". I used latex over oil primer, as recommended on the latex label. Perhaps the "oil is too brittle" folks are right. That's my current working hypothesis at any rate.
So this summer I tried a different approach.
One set of steps I pressure washed to blast off as much blistering paint as possible. Let it dry and sanded it, then applied the latex with no oil primer. The latex is a high quality 100% acrylic latex paint rated for exterior horizontal surfaces exposed to foot traffic and weather. On half the steps I applied the latex unthinned (as per label directions), on the other half I used thinned latex for the first coat (in order to penetrate better into hairline cracks and the spaces between the boards) and then 2 coats of unthinned.
On the other set of steps I removed all the treads and risers, and completely removed all previous coating with a planer, edger, and belt sander. I used a different approach on each of the 12 boards, including replacing some of the boards with new wood; but in all cases I coated all six sides (that's why I removed the boards). For example, on one of the boards I applied the latex directly to the wood without a primer. On another I used thinned latex as the first coat, then 2 coats of unthinned latex over that. On another I stained the board first with Cabot semi-solid deck stain, then applied latex over that (yes, I know that conventional wisdom says don't do this). On another I used an oil-based water-sealing product which claimed it was paintable, then oil-primed and latex topcoat over that (letting each dry thoroughly of course). I kept a record of how each board was prepared. In a couple of years I'll see the results. Hopefully, at least one approach will endure.
I haven't re-done the breezeway area yet, but the plan is to do it the same way as the first set of steps mentioned above (power-wash to remove blistering paint, then apply latex without oil primer). Removing the breezeway boards to paint the undersides and edges and ends is out of the question. Using oil in this area is extremely inconvenient - after power washing, the waiting period for proper drying would be a real problem. Oil requires absolutely bone-dry wood. Any moisture stops the penetration. Latex is far more forgiving in this regard.
The one question that remains unanswered, and the one that has offended and/or angered some posters to this thread, is the issue of thinning latex paint with water. I was hoping there might be an old-timer or two here who understood this issue and could shed some light:
Many latex paint labels say "do not thin". The question I was exploring is whether this "do not thin" exhortation is universally true, or whether there might be extenuating circumstances wherein in would be permissible, even beneficial, to thin just the first coat, to improve penetration into nooks and crannies and spaces between boards, as long as an unthinned second (or even third) coat of unthinned is applied.
I tried to find a suitable water-based primer for this application but was unsuccessful. I looked at MANY paint stores and home-improvement centers, and spoke with a few contractors and painter friends. I have yet to find a water-based primer that is rated for horizontal wood surfaces exposed to rain and foot traffic. One guy swore by Zinser 123, so I bought a gallon, but when I got home and read all the fine print, it categorically stated "not for use on horizontal surfaces exposed to foot traffic and water".
I've also read that you should always use a primer and topcoat from the same manufacturer to assure they are compatible. I'm not sure if this is true, or if true, why.
If anyone knows of a water-based primer designed for use on previously-painted weathered wood which has been power-washed to clean it and remove loose paint, and which is compatible with Sherwin-Williams 100% acrylic latex exterior porch and floor paint, please post.
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Ether Jones wrote:

I think I've finally found a (partial) answer to my question; I'll post it here for the benefit of anyone else who might be interested:
The major solvent in today's latex paints is water. But they also contain small amounts of organic solvents, such as 2-(2 butoxyethoxy) ethanol and trimethylpentanediol isobutyrate, which function as "coalescing solvents". These coalescing solvents play an important role in the film formation, and apparently the RATIO of organic solvent to water affects the film formation. At least that's what the technical discussion in the link below appears to be saying. SO... the reason why adding too much water could be a bad idea is NOT that there is "less binder" in the thinned latex, but rather that the thinned latex has the wrong ratio of water-to-organic-solvent... and this apparently affects the chemistry of the film formation process.
more details at this link: http://www.dow.com/ucarlatex/coatingsconnection/archive/0311.htm
The proof is in the pudding, though, I suppose. Yesterday I blasted the breezeway area of the porch with the power washer. Large sheets and small flakes of old paint were flying everywhere. But the test patches where I had applied thinned latex to scraped-bare wood 3 days prior held fast and showed no sign at all of coming loose or wearing off. So the plan is to use thinned latex for the first coat to penetrate into hard-to-reach places (like between adjacent deck boards, and where railing posts sit on the deck boards, and hairline splits in the boards); and topcoat that twice with unthinned. I'll know by next year if this approach is better than the latex-over-oil-primer approach I used 2 years ago which failed in one year.
Thanks to all those who contributed.
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wrote: I'll know by next

If it failed it was due to causes as yet unrevealed, likely improper application or inadequate surface preparation.
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NickySantoro wrote:

Perhaps, but the application and prep were meticulous. All treads and risers were removed and thoroughly scraped, wire-brushed, sanded, and brushed. Primed with oil primer all six sides. Top-coated with 2 coats of porch and floor latex all six sides.
So the other possibility is perhaps the conventional wisdom of latex topcoat over oil primer is not universally correct for all applications. FWIW, I spent 30 minutes in a paint store this afternoon reading the label of each and every different exterior primer, both oil and latex (8 or so different cans). Not a single one of them listed exterior wood floors or steps as an acceptable application. Some of the highly-touted brands such as Zinser 123 and Kilz explicitly excluded exterior wood floors and steps.
It will take a couple of years, but my experiment with the backyard porch steps should be most interesting:
http://groups.google.com/group/alt.home.repair/msg/1f2d2dd773730bb1?dmode=source&hl=en&output=gplain
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You wont know with your experiment till it fails, what if it peals in sheets in 4 years, well it could. Quit experimenting and follow directions. Primer for decks is often paint thinned properly, properly is the key.
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m Ransley wrote:

That was the whole point of the message to which you were responding: WHAT directions?
Can you recommend (by brand name and model number) even ONE primer whose labelling explicitly allows usage on horizontal wood surfaces exposed to weather and foot traffic?
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Just add some mineral spirits. Whats so hard about that. Gasoline works too.
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On 23 Aug 2006 17:04:16 -0700, with neither quill nor qualm, "Ether

By overthinning the latex paint, you break down the chemical bonding of the "glue" base which holds it together. Any paint over the top would be more easily removed.

Jus' cuz.

Blistering and peeling are indicators of moisture damage. Since the primer came up, too, I'd wager that it was the wood which was still wet.

Make POSITIVE SURE that the wood is dry, the primer is dry [I'd use all oil-based if it was available, all latex (including primer) if not.] As you have seen, 2 days at 85F wasn't enough to dry the wood after washing. Also, make sure it's properly rinsed. Soap films can be really tenacious. Give it a week to dry AND protect it from dew.
Another possibility arises when you paint things out in the sun. It's best to paint while it's warm and dry, but not in the direct sunlight if at all possible. That, too, can cause blistering as the outside layer of paint dries more quickly than the inside, sealing in more moisture than it normally would. (I've only read about this part, not experienced it firsthand.)
Also avoid cheap paints. Good, durable, long-lived paint ain't cheap.
G'luck!
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I agree with Jonpa..., most of the information was useful and informative. The posters replying to the thread didn't seem to grasp the idea of what was being discussed, and offered little in that direction.
Mineral spirits? Gasoline? Just follow the directions? The reason for using primer in the first place is to fill in the bumps, creases, and other imperfections on the bare wood. The same is true of the primer you spray on your car's body to avoid rust.
My problem isn't decking, mine is beehive lids that absorb huge amounts of moisture from the respiration of the bees clustering in winter. The wet wood lifts the paint and flakes it off. Acrylic primer doesn't seem to work at all.
As for the date, we're aware of it, Philo. We're wishing for a followup to the experiment concerning the thinned paint as a primer substitute.
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snipped-for-privacy@gmail.com wrote:

Quilt boxes . That is , a shallow tray above the cluster that's filled with wood shavings or other absorbent material . Do you have an upper opening for warm moist air to escape ? If not , I'm surprised you don't have cold water dripping on the bees , a sure way to kill a colony . I use an inner cover with an outer that's covered by aluminum flashing , no paint on my covers .
--
Snag



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On Tue, 1 Mar 2016 02:00:35 -0800 (PST), snipped-for-privacy@gmail.com wrote:

The funstion you are referring to is the filler. A "primer" enhances adhesion of the paint to the substrate. Thinned latex isn't much good for either.
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