aggressively thinning latex paint?

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quickly quoth:

Just paint the fucking boards and shut up, already!
Sheesh!
Steve
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Ether Jones wrote:

pigment your paint will be as strong but with less pigment per volume.
Paint has three essential functional products (sometimes lots more chemicals): pigment, binder, vehicle. Pigment is the color you want. Usually ground up stuff. Binder is what holds it together when it is dry. Vehicle is what makes it liquid enough to get from the can to the brush to the surface, and makes it run out flat. The pigment, without the binder (or thinned too much) would make it like milk of magnesia, white dust on the siding :o)

Quality paint rarely needs thinning. To thin it too much is to weaken it's ability to stay on securely.

them in one foot lengths. Lay the 16 pieces of cut boards in four rows of four. Should cover 16 square feet. Now pick them up, throw away 8 of them. Use the remaining 8 pieces to cover the same area.
Your thinned paint has binder spread too thin, I'm thinking. Might work.
Here is a link to additives, Floetrol (water base paint) and Penetrol (oil base). Penetrol is only one I have tried, for spraying. Works beautifully.
http://www.o-geepaint.com/cgi-bin/FrameIt.cgi?url=http://www.floodco.com
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Norminn wrote:

The question on the table is, *why*. See further discussion below:
EtherJones wrote:

Norminn wrote:

Your example is flawed; it is in no way analogous to what I wrote. Please reread my example more carefully. In my example, there was no binder "thrown away". Both boards have exactly the same amount of binder (and pigment) on them. So what makes one "weaker" than the other? Are you claiming that the added water somehow prevents the binder from polymerizing properly? And if that is what you are claiming, where did you learn this? Could you please cite some technical references.
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Ether Jones wrote:

I thought my example was pretty good, to illustrate that the diluted binder has fewer molecules to hang together and cover your wood. If you want a treatise on paint chemistry, go find one. You obviously understand factors that made your paint job fail, so why pursue methods that aren't recommended? I do exterior painting in the fall, when conditions are optimum for what I want to do. Dry, not too hot, not too cold, and comfortable enough to do all the right prep work. Have cleaned up lots of other people's sloppy work, so I consider that valuable experience. Common sense serves better than intimate knowledge of the chemical compounds, it seems.
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Norminn wrote:

The thinned latex has exactly the same total number of molecules of binder as the unthinned latex. Read the example again. Adding water does not reduce the number of binder molecules, it just increases the number of molecules of water.
Because the second portion has additional water, it is thinner and therefore more coats will need to be applied to use it all up. But once it's all used up, you've applied the same total number of binder molecules to the second board as you did to the first.

I've been looking. Haven't found one yet.

Because I want to understand WHY they aren't recommended. I like to understand why I'm doing what I'm doing. If the label on the paint can says "Do not thin", I want to know why. By knowing "why", I can determine under what circumstances it might actually be permissible, even beneficial, to thin (even though the label says "no").

Common sense is good yes. But sometimes what passes for common sense is a collection of urban legends and anecdotal experiences. That's why it's good to ask "why". I'm not saying that's true in your case. You seem to have some substantial experience.
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A thought just occurred to me which might be germane to this discussion. Perhaps someone familiar with how latex paint works could comment.
My understanding is that latex paint binder consists of monomers in water solution.
When you apply a coat of latex paint, and the water dries, the monomers come out of solution and begin to bond together into polymers. This bonding action forms the strong film. Once the polymers form, they are no longer water-soluble. That's why the film is water resistant, even though the original vehicle was water.
Now, what happens when you apply a second coat of latex? Obviously the process repeats itself. BUT, in addition to bonding with EACH OTHER, do the monomers in the second coat ALSO bond EQUALLY EFFECTIVELY with the polymers in the first coat, to create one seamless film (assuming the first coat was kept clean) ? Or, is the bonding between the monomers of the second coat and the polymers of the first coat only PARTIAL, so that what you get is two SEPARATE films which are bonded together, but the bond BETWEEN the two coats is not as strong as the bond WITHIN each coat?
If the latter is true, it would explain the difference between boards one and two in the example I gave in an earlier post. The first and second boards would have the exact same total film thickness, but the first board would have fewer, thicker layers; and the second board would have more, thinner, layers. What this means in practical terms as far as the quality of the paint job is still arguable I suppose.
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Ether Jones wrote:

thinning the paint too much with water keeps the molecules from bonding because they are spread too far apart. Reason I used the cut boards (molecules of paint binder) example - you can't cover the same area with half the material, whether microscopic or macroscopic. Capiche?
The boards you refinished likely had some moisture in them, having been washed two days before. Not washed, but without impermeable finish, they would be damp from being outdoors. Boards fastened onto a deck, without being finished on all sides, would hold moisture. So, when finish is applied, sun hits the deck, the moisture expands and the paint film blisters or cracks.
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Because it IS film. i.e. part of the binder. But it flows better. Anyway, to fill cracks and other small imperfections, buy a paint specifically for the job. Sherwin Williams sells PrepRite High Build Primer/Surfacer, or even Block Filler (which is meant for concrete, I don't know how well it would work on wood). Other companies probably have similar things.
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jeffc wrote:

No disagreeing with you, but where did you get this information? There is no information on the product label, and the MSDS lists no ingredients at all.

I have looked and looked, and asked many contractors and paint store gurus, and no one has been able to recommend such a product for the application at hand. Remember, this application is for exterior, horizontal, previously painted, weathered, wood, exposed to sun, rain, snow, and heavy foot traffic. If anyone knows of a specific product name and manufacturer for a product like jeffc has mentioned, please post it.
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Just do what I did. I wrote to the company and asked them to please send me the private patent information that contains all their ingredients and trade secrets. They sent them to me immediately.
Steve
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Steve B wrote:

The sarcasm is misplaced.
If you don't know what's in the product, don't be telling people you do.
By the way, patents are not "private". If it was patented (which it is not), that information would be publicly available.
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wrote

Good God, Man. Do you beat dead horses for a living, or just for fun?
Steve
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Do what the deck paint label says, or call the manufacturer. For oil deck paint the usual recomended way by manufacturers that is printed on labels is thin the oil paint with thinner. Ive only thinned latex to make it original in thickness after it has thickened by air, Ive never thinned to spray. The usual max recomended thinning of latex is 10% for spraying. Each product is different, follow its instructions. Your previous failures may be to damp a wood [ use a moisture meter ] I do. Or to hot in sun, to humid, to cold etc etc. Or even crappy paint.
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m Ransley wrote:

Just got off the phone with the tech support person for the latex I am using this year. What she said surprised me but also fit the facts of my personal experience. She said DON'T USE PRIMER. When I asked why, she said there ARE NO PRIMERS that hold up well to foot traffic. Well, that certainly is in agreement with my previous experience, and would explain why the paint on my porch steps failed so quickly.
Two years ago I oil-primed and latex-topcoated the porch steps, and the system failed after one year. The paint was adhering to the primer, but the primer was peeling from the wood. The latex I used back then was Dutch Boy Porch and Floor, and the label directions said to use an oil primer, so I did. In an earlier post, I speculated that the reason for the failure might be that the "conventional wisdom" (latex topcoat over oil primer) did not apply to what I was trying to do (horizontal wood exposed to weather and foot traffic). Looks like that might be correct.
The porch and floor latex I am using this year (made by Sherwin Williams) does NOT say to use an oil primer, or any primer for that matter.
The tech rep also said that even though the label says "do not thin", it is OK to thin with water up to 12% FOR THE FIRST COAT ONLY to improve penetration into hard-to-reach places as long as there is a second, unthinned coat applied.
At any rate, the next couple of years should be interesting to see what happens. One set of steps I power-washed, let dry, and painted with no primer, just like the label said. On a few of the steps I thinned with water for the first coat. The other set of steps I disassembled, planed, power-sanded, and applied paint/primer/stain/sealer in many different combinations to see which would hold up better.
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On Tuesday, September 5, 2006 10:03:57 AM UTC-4, Ether Jones wrote:

Mr. Jones, I commend you on your patience & methodology. Both on how you h andled this thread, as well as your experiments with your steps.
I am disappointed however, that you have never posted the results/findings of your investigation. Although I can hardly blame you based on replies & feedback you were getting from other posters. But I would appreciate very much for you to kindly share what you have learned.
You express yourself clearly & concisely, your questions are valid & pertin ent and your logic has been sound. You have a genuine thirst for knowledge & a hunger for the truth. You are not ego-driven like nearly all of those who commented on your question (I can't say "answered" because none did, a nd even saying "responded" seems to imply more relevance & substance than m ost posts contained)- you were merely seeking information, which in the end you were able to obtain on your own. It is rather disturbing how poor the average/typical levels are for such ba sic skills as reading, comprehension & short-term memory, which this thread exemplifies. It's baffling to me why everyone seemed to get so worked up, trying to turn it around & criticize the question or you- even resorting to swearing & name calling all because THEY were unable to answer your questi on or even provide any truly useful, pertinent information. People can be so ridiculous, silly & ignorant.
In any case, thank you! I found the information you shared very helpful and informative.
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On 12/12/2014 11:49 AM, snipped-for-privacy@gmail.com wrote:

!!!LOOK AT THE DATE!!!!
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The best technical explanation is simply that there are products made specifically to do that, and they are going to do a better job than using water.
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jeffc wrote:

Well no offense jeffc, but that's certainly not a technical explanation and not very helpful.
BUT... if you find answers like that satisfying, more power to you. Vive la difference.
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I guess I'm stupid. I totally understood what Jeff was saying. I do the same things when traveling by airplane, going over a bridge, or turning on the lights.
I really don't have to understand everything that makes them work, and I sure couldn't explain it to a Piled High and Deep type of person in a conversation, but then, I'm just one of those stupid nontechnical types.
Steve
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Ether Jones wrote:

This thread has a distinct odor of troll .. why don't you take your vast scientific conversation to a paint chemist at a paint company? The whole idea behind paint is to keep wood from getting split, cracked and weathered, so we yokels on ahr share our experience to try to help others. Paint products that I am familiar with say "don't thin more than 10%", "sand weathered wood", "apply to clean, dry surface", "prime bare wood", etc. Since painting is a good deal of work, the preparation being the most tedious, we haul out the brushes and tarps and get the job done before the item to be protected turns to crap. You have been offered good faith advice, but challenge everyone who replies. By the time you get around to doing the project, the house will be falling down.
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