Guess it contains the binder, so without as much heavy, ground up
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.
Well, try this: take four boards, each 12" wide by four feet long. Cut
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
The question on the table is, *why*. See further discussion below:
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
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.
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.
A thought just occurred to me which might be germane to this
discussion. Perhaps someone familiar with how latex paint works could
My understanding is that latex paint binder consists of monomers in
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.
I don't know anthing about monomers and polymers. By your description,
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.
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.
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
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.
The sarcasm is misplaced.
If you don't know what's in the product, don't be telling people you
By the way, patents are not "private". If it was patented (which it is
not), that information would be publicly available.
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.
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
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
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.
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
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
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.
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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