My painter wants to dilute my Kilz (waterbased) undercoat to make it
work better in his spray gun. This is exterior application on OSB.
For protective coverage does this mean in order to get same protection
that more coats need to be applied..or is this incorrect thinking?
My correct e-mail address is gno52 (not gn52)
Fake adddress given to avoid spams
Yes...You are correct....I used to be a Paint Chemist..Retired now....It
will reduce the 'Solids' of the paint...so when the 'volatiles' are gone for
a particular 'thickness' shall we say...........There will be 'less' of the
solid left ..thus thinner dried coat....So 'Yes' you would have to apply
more coats..depending on how far he 'dilutes' your paint....
- Nehmo -
What did you do as a Paint Chemist? Did you have some particular
education in the field? And besides being a chemist, do you have any
actual experience painting?
I'm studying paint and stain now, and I'm amazed at how widely opinions
of professional painters differ. I don't have the experience to tell
Yes...I am (or was)..an Industrial Chemist...I am now retired....I worked 24
yrs in Research and Development.....I formulated paints..to shorten the
query for you....I worked for Large World wide Paint Companies.....I have
worked on Automotive ,House Paint,Industrial Coatings,Marine Paints,
Industrial Maintenance Coatings..etc , etc,..Does that give me any
I was answering a simple 'query' !
It'll be fine IFF the paint's instruction include being able
to spray it, and if the instructions are followed. To spray
paint, it's almost always necessary to thin it to get it to
operate correctly in a sprayer, and the manufacturers know
that, and indicate on the can if it should not be thinned.
It's not true that more coats need to be applied although
the logic would seem to say that. If a gallong brushed on
covers x00 sq ft, and a gallon sprayed on covers the same
x00 sq ft, then that is exactly the same coverage. And
that's what you'll get when the manufacturer's instructions
are followed, especially by a professional painter.
All that said, I have a personal aversion to latex primers:
I feel you should be using an oil based product. But that's
No it's not. If you brush on the gallon straight from the can, you get a
gallon (4 quarts) of paint on the surface. If you add a quart of water
(just to make the math easy), then you have 5 quarts of "paint". If you
then spray on 1 gallon of this to the surface, you are only getting 4/5 of a
gallon of original paint on the surface (in terms of solids.) You'd have to
spray on the entire 5 quarts on the same surface to get the whole gallon on
there, and this will often result in dripping (especially since the paint is
If your painter has to thin the paint then he is most likely using air to
an airless sprayer would not need to be diluted .Use a .015 tip and go for
"If latex paint were ment to be thinned, the water would already be in the
"fsteddie" <epearlatprexardotcom> wrote in message
Yes...I agree with you...You can spray (and if the painter were really
Professional)....Airless Spray.....No need then to 'thin' the paint out and
drop the 'Solids' and the 'Volume Solids' ...<G>........Let...Nehmo...learn
about more than Just 'Paint and Stain'.....Let him learn about 'Application'
..OF..The 'Paint and Stain'.....I hope they also train him in this as well
It's correct, to a point. Most manufacturers provide a dilution ratio
for spraying, but common sense is usually fine. Dilute by half, spray
twice. Or similar. As long as the coverage rate of the original
paint is used (in other words a 400 Sq Ft coverage for a can of paint
isn't used for 800 Sq Ft just beacuse you thinned the paint) the end
result is pretty close to the same.
The kicker is that many paints are actually applied heavier than need
be, so dilution may vary. In addition, absorbtion by substrate can
affect coverage as well. Plus this is a primer, where solid coverage
is less of an issue than with colors.
When all is said, it's hard to apply too much paint and it costs far
more for labor than paint, so an extra coat because you thinned the
paint is cheap insurance of good coverage.
That's not the point. The point is labor costs money. They charge by the
square foot knowing how much time it will take them. It takes more time to
do 2 coats than 1. And their charge reflects this. i.e. it would cost less
if they didn't have to.
Diluting will reduce solids per unit of volume. Diluting liquid
finishes is a common necessity and typically calls for more
applications for same coverage. Wood finishers frequently dilute a
varnish for wiping it on instead of brushing and EXPECT a thinner
final coat when dry. Don't see any anomaly in your thinking.
I would be more worried about my painter. I can't imagine a
professional painter using anything other than an airless for an
exterior paint job. I can't imagine an airless that can't push
Keep the whole world singing. . . .
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