Thanks for the detailed explanation.
It is my understanding that here in Arizona the moisture barrier is
reversed compared to homes in areas that are cold/freezing. Think
about it we run AC here, making the interior colder than exterior at
least 9 months a year. I don't run it at all if I can help it. but
you see the concept of the inside being cooler than the outside.
However, when working on the exterior wall to reposition the stove top
vent hood; the barriers looked like they were still set up for a
'freezing' climate. consisting of
joint compound skim coat
nylong netting[ chicken wire gaps
fluffy fibre glass insulation blown in between the studs
1/2 inch sheathing
two layers of tar paper
Upon running the stove top fan am convinced the house is, nor could
ANY house could be, tight enough to need super breathing requirements.
I don't think you'll have any problem either.
Not only is Arizona a dry climate, but cold air escaping through a hole
in your vapour barrier is going to warm up and absorb any moisture in
the walls, which is the opposite of what happens in the winter where I
I'm just surprised that it's taking three coats to get a decent looking
coating over your stucco. I expect that's because the first coat you're
putting on is acting as a sealer for the second coat. I think priming
with a latex primer would reduce the amount of elastomeric coating you
have to put on.
All acrylic and PVA resins have enough elasticity to stretch and shrink
with wood outdoors, and primers don't need to have UV resistance and
mildew resistance because they're meant to be covered by a top coat that
would keep the sunlight and moisture off of them. If you ever see latex
primers listed as an "Interior Latex Primer" or an "Exterior Latex
Primer", it's likely that the only difference is that the latter uses a
coalescing solvent that smells a lot, whereas the former uses one that
doesn't. In hospitals and commercial settings it's often important not
to have the latex primer or paint smell as the coalescing solvents
evaporate because some people can get headaches from inhaling those
fumes, and generally, the less the solvent smells, the less people will
be affected by it.
When I did the exterior walls as a SECOND coat over previous attempts,
I got these vertical 'llines' that show up because of pattern
recognition. Someone said wait a month they'll disappear, but I think
the lines come from a change in surface 'smoothness' which will never
change with time. They do seem to be diminishing with time, not sure
As an experiment, I painted only half a cupalo(sp?) tower on the south
side of the home. A week ago, I only painted half vertically because
of the height and difficulty to reach. Today I painted the second haf
and there is absolutely NO vertical line caused by an overlap! There
is an apparent change of color, which could be attributed to drying
time. We'll see.
So here it is. Wet overlap shows up, but dry overlap does not ?! That
makes no sense to me, but if it's true I'll simply adjust my painting
Both wet and dry overlap should result in the same increase in colour
density until you reach complete hide of the substrate colour. Once
you're at complete hide, adding more coats or more paint anywhere won't
cause any change in colour density.
Not sure I'm fighting 'colour density' because
1. the first coat just appeared 'blotchy', but appeared to give full
coverage, with any pattern underneath caused by variations of sun
bleaching, etc do not seem to translate through to change the
apearance of the first coat.
2. with a very solid looking colour, the second coat seems to have
these vertical stripes of overlap.
I don't see any pattern, well not much, burning through from the first
The more and more I look at this, the more and more I think I'm
fighting surface textural changes. Less coat - surface is slightly
rougher. More coat - the surface is slightly smoother. And, the eye is
quick to perceive a pattern, any pattern.
But, your point is well taken, I have completely discounted the
potential for colour density changes. From memory, the eye is supposed
to be more sensitive to colour shift than to light/dark shift. With
that in mind, it would explain why the first coat hasn't burned
through to the second, only the second shows. No, if colour density
were an issue, it should show up in the second coat over the first,
and does not seem to. I'm caught between hoping it's only a matter of
true curing/drying time and just careful applications.
I add Floetrol at 4 oz per gallon [recommended amount] and the paint
seems to still be sticky, gooey, and dry before I can go very far
along the wall. The paint even forms a slight scum on top of the
surface in the container. Keep in mind this is evening painting, and
is painting on the shaded walls, not in the sun, nor any surface in
the sun. So there should be nothing except our 10% humidity
accellerating the paint's drying.
No appears to have been done all at one time. Plus, thiis specific
area is not large, around 8 feet high by 10 feet wide.
I have seen their starts and stops, but this is not it. Their patterns
are horizontal. My painting patterns are vertical, since I paint from
top to bottom.
Why does that surprise you? If you overlap wet paint you are retarding what
was already there - partially dried - from drying further. It will,
eventually. In addition to difference in color, you will also get a
difference in sheen.
IIRC, you are painting over previous paint that is chalky. On an old house.
Lord knows how many coats of paint are on it but that old, chalky paint is
going to suck moisture out of the new paint. Put on a coat, moisture is
sucked; come back later and apply more paint overlapping the old and you are
going to get a stripe where they overlap because the overlapped area has
been sealed. Not hard to understand.
What?! retarding paint's drying changes its colour?! Difference in
sheen I believe. But that's due to the surface gumming up. I used to
use Easy OFF Window Cleaner, comes in an aerosol spray can, to lightly
mist the surface of latex and be able to brush over any variation
making it uniform, but alas, they've discontinued that product. Used
to be able to use that product to go back hours later nd still make
First, coat should be sensitive to what's underneath. That's why I
chose to water wash and physically scrub the old coat. Which did show
a colooured run off of chalky paint and dirt from wherever. I saw a
difference with the way the paint went on and recommend always
cleaning the base surface. But, the problem that prompted me to post
is NOT with respect to the first coat, but the second coat, which of
course is going over an almost acceptable surface of paint. Second
coat was actually an experiment. I don't want to do two coats on this
house, too expensive, and too labor intensive.
I didn't say that. I did say that paint can take many days to completely
dry/cure and that the color and sheen won't be uniform until that time has
Let me try to clarify...
1. First coat over existing, old, chalky paint. Coat dries - dries, not
cures - relatively fast because old paint absorbed some moisture.
2. Second coat, partially lapping #1. The lapped part is a different color
and/or sheen because the first coat under it has sealed the surface and the
lapped part is drying/curing more slowly than paint over the old, chalky
I'm trying a new section that has been physically scrubbed with brush
and plain water. We'll see what happens over that.
I hope all these problems are just a matter of drying. However,
Where I put the two coats has the 'decidedly' obvious stripes ONLY
from the last coat. Been drying since I started this thread.
On the tower which was difficult to reach so I painted one half side,
waited three days, painted the other half; has absolutely NO line at
the overlap, but does appear to be two diffierent colors! Oh well, win
one lose one.
Same thing...new paint will dry, next coat will dry except any overlap will
which dry more slowly. Ultimately, all will look the same assuming you
mixed the paint well.
Out of curiosity, why do you paint from the bottom up? Gravity is your
I thought I said I painted from the top down.
Don't get me started on my ability to use the English language! I
absolutely say the opposite of what I mean. In meetings, people marvel
at that trait.Up is down. Down is up. Spent too much, yeah.That kind
of thing.I say it's all part of dyslexia that is getting worse while
aging. What's really irritating is that with dyslexia the sentence
looks absolutely correct until finally noticed!
There seem to be 2 opinions on painting.
One is for stucco over concrete block which is common in the south. It
is very common to paint the stucco.
The other is stucco over wood frame. The advice is to redash, which is
the thin stucco material used as the surface on the original stucco.
Paint turns the stucco into a surface that requires relatively frequent
repainting. You don't have to redash very often. (I don't know why that
logic doesn't apply to cement block stucco.) Redash can be pigmented.
Thanks for your usual detailed information.
The advice on painting stucco, in particular, is do not use oil paint,
which prevents 'breathing'. The outer surface of the wall has to
'breathe' better than inside the house surface. It can be a particular
problem on older houses that do not have the vapor barriers common on
I would note there is also EFIS. Don't know if it is still being used,
but there were some horror stories, which may have been from improper
use, where there was extensive mold inside the walls. Very expensive to fix.
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