blueman wrote:
"Mike Marlow" writes:
blueman wrote:
Ahhh my HF gun comes with a 1.4 tip... and as I am just now learning
that may make it come out to thin though I'm not sure I understand
the mechanics of it. So perhaps that is part of the problem...
Nope - the tip does not make it come out thinner - smaller tips
require thinner material. For a 1.4mm tip you would want quite a
thin material, or it will not spray it well. Start adding more
reducer (water for water bases materials) and test shoot until you
get a good pattern. Increment the amount of reducer by 10% or so
until you get t good, shootable mixture. Keep note of how much
reducer you are adding so that when you get to the point where it's
spraying well, you can reproduce that ratio of reducer to material
later on.
Does one that get into a bit of a paradox:
- Too thick means it doesn't atomize and coalesce properly
- Too thin means it sprays nicely but runs and sages unless coat is
applied thinly
I tried to correct this misunderstanding of yours in a past post. You are
too worried about how thick you are spraying it on. Don't be. Spray it on
like a layer of plastic you are stretching across the base material. If it
takes 3 coats - it takes 3 coats. If it takes 10 coats, it takes 10 coats.
Follow the manufacturer's directions for overcoats and just keep building it
up as necessary. The only thing you need to think about is imagining that
you are stretching a piece of plastic over the surface you are painting, and
making your spray application do that. If you are getting runs and sags
(and don't worry about that - I *still* shoot some once in a while), then
you're moving too slowly. Practice on scrap. Hear me? Practice on scrap.
Which would seem to mean that if I use my current tip, but thin then I
will have to put on more thinner coats.
Yup. You got it. No problem with doing it that way.
While getting a wider tip would spare the need for adding reducer and
would allow me to apply a relatively thicker coat without sagging or
running.
And bring about other problems like shrinkage. There is no short cut to
doing it right. It sounds like you're looking for the one shot finish, and
that does not exist. Yes - a larger tip will put more down at once, but
then drying times extend, shrinkage enters into the picture, and if you do
run - you really run... or sag. It's more about technique than it is about
tip sizes. You really have to practice with that gun on scrap and get the
feel for it.
I just shot a bunch of primer through a detail gun. Would not lay on a
heavy build coat with the tip that I had. So... had to reduce the mixture
and shoot slower in order to get a good we coverage. Oh well. That's what
you do. If you are looking for the perfect tip for the perfect spray
material, on the perfect target - you're going to be very disappointed. Mix
up something your gun will shoot and.... practice.
Am I understanding this tradeoff properly?
Yes, but my fear (and I may be reading you wrong...) is that you're looking
for a silver bullet. Spray painting is all about adapting to the situation.
Humidity, temperature, viscosity, and a lot of other factors, enter in on
every single spray job. That's why I'm so adamant about pushing your to
experiment, learn your gun, and practice. You can overcome any issue with
spraying if you understand your gun.
Also, would having the right size tip and/or right viscosity typically
allow me to lower the HVLP inlet pressure (I now have it cranked up to
about 30psi but ideally, I know I could or should go a lot lower...).
Yes. The first thing you have to do is get the reduction such that your gun
can shoot it. So - reducing it to the point where you can get your pressure
down is very important. You don't really have HVLP anymore if you're
shooting at those high pressures. You're blasting more material into the
air than you realize. Might just as well grab a decent siphon gun and have
at it. So, once you get the reduction right - you know what I'm going to
say...
--
-Mike-