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Spraying Latex with HVLP



 
 
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  #1  
Old May 23rd 11, 05:19 AM posted to rec.woodworking
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Posts: 2,091
Default Spraying Latex with HVLP

I have a Graco 3 stage HVLP. Love it for shellac, lacquer, poly, dye,
etc. I bought a bigger tip. I have a 2qt pot that takes pressure from
my compressor then a material line out to a gun which has the hvlp air
also. It blew the BIN primer well but the Latex\Enamel Semi Gloss was
almost to heavy to spray but I got a decent spray after tweaking the
flow\air\etc.

I am getting small air bubbles in the paint. Just pin head sized but
lots of them they don't pop and end up leaving nibs once dry.

I know this setup is barely strong enough to blow latex but wondering
if anyone has any ideas. I did use some flowtrol. Not sure if that was
the issue or if I should use more or what.

I am pretty sure I had the gun and lines clear of the alcohol from
cleaning the bin and I sprayed one side of 6 cabinet doors and was
still getting bubbles although tweaking to lees paint seemed to help a
bit.
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  #2  
Old May 23rd 11, 05:39 AM posted to rec.woodworking
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Posts: 160
Default Spraying Latex with HVLP

SonomaProducts.com wrote:

I have a Graco 3 stage HVLP. Love it for shellac, lacquer, poly, dye,
etc. I bought a bigger tip. I have a 2qt pot that takes pressure from
my compressor then a material line out to a gun which has the hvlp air
also. It blew the BIN primer well but the Latex\Enamel Semi Gloss was
almost to heavy to spray but I got a decent spray after tweaking the
flow\air\etc.

I am getting small air bubbles in the paint. Just pin head sized but
lots of them they don't pop and end up leaving nibs once dry.

I know this setup is barely strong enough to blow latex but wondering
if anyone has any ideas. I did use some flowtrol. Not sure if that was
the issue or if I should use more or what.

I am pretty sure I had the gun and lines clear of the alcohol from
cleaning the bin and I sprayed one side of 6 cabinet doors and was
still getting bubbles although tweaking to lees paint seemed to help a
bit.

I'm no expert in the field of painting but did a kitchen cabinet painting
job for a customer, used Zinnser BIN which I love and then sprayed water
based enamel with a HVLP guy. The job came out excellent to my standards and
the customers. I found thinning the with water worked well. Also found out
the hard way when spraying cabinets, work outside in not the other way
around or you will get over spray drying on paint thats drying causing a
rough finish and lots of sanding. I'd stay away from latex if you're
planning on sanding it. Latex does not sand well. I would not use latex
except on walls, not on cabinets or doors.
--
"You can lead them to LINUX
but you can't make them THINK"

Man. 2010.1 Spring
KDE4.4
2.6.33.5-desktop-2mnb
  #3  
Old May 23rd 11, 04:43 PM posted to rec.woodworking
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Posts: 10
Default Spraying Latex with HVLP

On 5/22/2011 9:39 PM, Rich wrote:
SonomaProducts.com wrote:

I have a Graco 3 stage HVLP. Love it for shellac, lacquer, poly, dye,
etc. I bought a bigger tip. I have a 2qt pot that takes pressure from
my compressor then a material line out to a gun which has the hvlp air
also. It blew the BIN primer well but the Latex\Enamel Semi Gloss was
almost to heavy to spray but I got a decent spray after tweaking the
flow\air\etc.

I am getting small air bubbles in the paint. Just pin head sized but
lots of them they don't pop and end up leaving nibs once dry.

I know this setup is barely strong enough to blow latex but wondering
if anyone has any ideas. I did use some flowtrol. Not sure if that was
the issue or if I should use more or what.

I am pretty sure I had the gun and lines clear of the alcohol from
cleaning the bin and I sprayed one side of 6 cabinet doors and was
still getting bubbles although tweaking to lees paint seemed to help a
bit.


....I can't get latex to spray "right" out of my hvlp, either. I
ended-up at HD and, too cheap to go for the real deal, bought a Wagner
"Paint Crew" airless for a couple of sheets. It works like a
champ...little bit of a mess, but the results are pro.

cg
  #4  
Old May 23rd 11, 05:38 PM posted to rec.woodworking
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Posts: 2,091
Default Spraying Latex with HVLP

I would not use latex
except on walls, not on cabinets or doors.
--


Well, at Home Depot I bought what is labled as enamel semi-gloss as I
heard it was a little thinner than latex. The guy at HD told me even
though it says enamel it is still latex. Then at Lowes I saw their
interior semi-gloss enamel say latex elsewhere on the can. I am
confused but that is pretty normal.

I can do the cabs I am building by hand but I want to install 11 new
pre-hung 6 panel doors and I did two as a trial effort and the nad
painting (I used a brush) took way too long. I did it in saw horses,
one side at a time, two coats, forever. I was hoping spraying would be
fast and nice.

I wonder if some of this Rust Oleum oil based paint would be
appropriate? I used it to paint part of my truck and it was thin
enough to spray nicely.
  #5  
Old May 23rd 11, 05:57 PM posted to rec.woodworking
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Posts: 6,062
Default Spraying Latex with HVLP

On May 23, 12:19*am, "SonomaProducts.com" wrote:
I have a Graco 3 stage HVLP. Love it for shellac, lacquer, poly, dye,
etc. I bought a bigger tip. I have a 2qt pot that takes pressure from
my compressor then a material line out to a gun which has the hvlp air
also. It blew the BIN primer well but the Latex\Enamel Semi Gloss was
almost to heavy to spray but I got a decent spray after tweaking the
flow\air\etc.

I am getting small air bubbles in the paint. Just pin head sized but
lots of them they don't pop and end up leaving nibs once dry.

I know this setup is barely strong enough to blow latex but wondering
if anyone has any ideas. I did use some flowtrol. Not sure if that was
the issue or if I should use more or what.

I am pretty sure I had the gun and lines clear of the alcohol from
cleaning the bin and I sprayed one side of 6 cabinet doors and was
still getting bubbles although tweaking to lees paint seemed to help a
bit.


I have sprayed, supervised spraying and problem solved spraying issues
for decades.
Not always successful but somewhat educated I suggest that latex, when
sprayed, should have a serious whack of power behind it and that
spells: airless. Flowtrol is your friend, so is a bit of water.
Temperature and humidity are huge factors as well.
I seldom comment on spraying techniques as there are so many variables
that will/can drive you nuts.

Think about it... that stuff is rubbery (In the UK they call it
emulsion) so to atomize it requires power.
Yes it can be sprayed successfully, I have on many occasions, but you
need to stop thinking that **** as being paint. The 'aint' component
of the word sums it up.
  #6  
Old May 23rd 11, 08:03 PM posted to rec.woodworking
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Posts: 2,091
Default Spraying Latex with HVLP

The 'aint' component
of the word sums it up.- Hide quoted text -


Nice.

I think I'll look for some oil based "solution" (pun).
  #7  
Old May 23rd 11, 08:42 PM posted to rec.woodworking
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Posts: 5,892
Default Spraying Latex with HVLP

On Sun, 22 May 2011 21:19:00 -0700 (PDT), "SonomaProducts.com"
wrote:

I have a Graco 3 stage HVLP. Love it for shellac, lacquer, poly, dye,
etc. I bought a bigger tip. I have a 2qt pot that takes pressure from
my compressor then a material line out to a gun which has the hvlp air
also. It blew the BIN primer well but the Latex\Enamel Semi Gloss was
almost to heavy to spray but I got a decent spray after tweaking the
flow\air\etc.


I had trouble with my HF HVLP conversion gun spraying sg latex enamel.
I couldn't buy a larger tip so I thinned with floetrol. It finally
shot OK after I warmed the mixture to 100F or so.


I am getting small air bubbles in the paint. Just pin head sized but
lots of them they don't pop and end up leaving nibs once dry.


How close are you spraying?


I know this setup is barely strong enough to blow latex but wondering
if anyone has any ideas. I did use some flowtrol. Not sure if that was
the issue or if I should use more or what.

I am pretty sure I had the gun and lines clear of the alcohol from
cleaning the bin and I sprayed one side of 6 cabinet doors and was
still getting bubbles although tweaking to lees paint seemed to help a
bit.


It sounds almost as if you're flowing so much liquid that the air is
foaming it before it hits the project. It would take a whole lot of
air pressure to do that, though, I'd WAG.

Have you called either Graco or Flood about it yet?

You also didn't state how you mixed the floetrol into the paint, but
bubbles in paint usually don't transfer whole through a gun. Good
atomization should take care of that.

--
Doubt 'til thou canst doubt no more...doubt is thought and thought
is life. Systems which end doubt are devices for drugging thought.
-- Albert Guerard
  #8  
Old May 26th 11, 08:01 PM posted to rec.woodworking
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Posts: 2,615
Default Spraying Latex with HVLP

Hmmmm.....

Let me preface by saying this is my own practical experience, and
anyone else's may differ.

First, a three stage gun/turbine like a Graco is plenty of machine to
spray latex.

Time to woodshed the gun/material setup.

An HVLP is different from a an HVLP CAS gun, which is what most folks
have. In theory, these are the same because they both use a lot of
air at low volume. Similarites stop there. The "connected to my
compressor HVLP gun" is simply a different look at the classic high
pressure guns.

Yours (in my mind) is the real HVLP, although I do love my two CAS
HVLP guns. The biggest difference is that almost all turbine guns use
about 5psi pressure to push the paint in front of the air cap, as
opposed to letting gravity or a 100% siphon system feed the gun. With
that in mind, poor mixing technique can indeed introduce bubbles in
your spray material. Not a problems with the old high pressure guns
as they literally did atomize the paint, blowing into tiny droplets.
After careful examination of a recently sprayed surface, you will see
that turbine HVLP is more of a controlled splatter. Today's finishes
are made with the sprayer in mind, and are most forgiving I have ever
seen.

With all that in mind, here are my suggestions based on my 12 year
love affair with my 4 stage Fuji HVLP, and a brief but productive
affair with a pal's 3 stage Turbinaire.

- Toss out the Floetrol. That crap is relic of the past, and is only
used by people like me when they have an open can that has started to
cure. YOU don't need it. I haven't bought that stuff in 10 - 12
years, and no professional painters under 65 use it. Trust me,
today's paint formulations assume a professional will be spraying.
Call your coatings rep; he/she will confirm

- Make sure you are using the best quality coating you can afford.
Sherwin Williams, Ben Moore, etc., all have a top line that is great.
When using my buddy's borrowed Turbinaire three stage, I was able to
spray the top line SW semi gloss enamel with no thinning. A lot has
to do with particulate size, colorant, and the base material used in
material formulation. (For example, SW is zinc oxide based, and
Glidden is clay based)

- Try shooting without thinning. Could be a surprise there. If you
need to thin, don't overdue it. (Although I have hit SW top line
enamel 20% before with no ill effects!)

- Thin good finishes with filtered or distilled water. A gallon
costs .99, and it will do almost five gallons of paint. Cheap.

- Turn the gun air OFF. Start a test shooting batch with a 10% thin.
Open the coating feed about 3/4 of the way. Slowly open the air
pressure till you get about a half feed. Spray a test area on a piece
of primed or previously painted wood or sheetrock. This method won't
work on bare wood. You should spray out a nice, but thin coat. In
another area, open the the pressure valve a bit more, and see if you
are still getting a good coat. Wait about 20 minutes and check to see
if you have bubbles

- if you do, toss out the paint in the gun and clean it well. This
shouldn't be a big deal since you are thinning by volume; you only
need a small batch of about 4 oz each to get an accurate batch sample

- Reduce to a new mix of 15%. Repeat. While all guns and shooting
conditions aren't the same, most seem to prefer about a 10% to 15%
thin, with the pressure at about 1/2 to 3/4 open. I installed a
regulator gauge on my gun though, as I couldn't always tell where I
was with a face full or respirator. Since you are doing this
professionally, I would strongly suggest you do the same for the sake
of repeatability

- I have found that a 1.7 tip works best on my buddy's gun for latex,
thinned as above dependent on spraying conditions. On my Fuji with a
1.8mm aircap, I spray enamels unthinned unless it is really cool where
I am spraying

- Some finishes shoot betterhan others, so I would try a quart of top
line products from different manufacturers and see which ones you like
and your equipment like. I can't stress enough that unless your gun
is actually broken, you have an excellent setup that you just need to
practice and test with coatings to make sure you have it all as good
as you can get.

- Watch your technique. HVLP guns are actually set to spray patterns
similar to our old high pressure guns. If you are newer to spraying,
it is important to find your gun's sweet spot. As a general
guideline, for this kind of spraying, your aircaps will work best at
about 8" from the surface. That isn't much, but it is also one of the
reasons you have such efficient material transfer. It is also the
reason you use lower pressure; the material doesn't have far to go.
It is easy to hit the surface so hard you get bubbles. But think it
through; a thinned finished with too much pressure will almost always
yield bubbles.

An easy way to tell you have too much pressure is if you spray and
find yourself in room full of drift, or you are using the same amount
of paint as you do with an airless or high pressure setup. The
bubbles are just another indication of too much pressure. It sounds
to me like you haven't thinned enough, and your pressure is too high
to try to make up for it, slinging the paint on the surface.

Make sure you are as close to that 8" as possible when testing.
Even an inch makes a difference one way or another, and the actual
sweet spot for my Fuji is about 8 - 9".

Finally, if all else fails, check this out:

http://www.spraytechsys.com/literatu...P_training.pdf

It is one of the most comprehensive, intelligent discussions of
practical HVLP use I have ever seen. Good stuff. And while the cap/
orifice tables won't be the same for your fun (such as size 4, or size
3, etc.) since they put the actual orifice size on one of their
charts, you can call Graco and they will tell you the equivalent.

Let me know if any of this helps.

Robert
  #9  
Old May 27th 11, 12:43 AM posted to rec.woodworking
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Posts: 2,091
Default Spraying Latex with HVLP


Let me know if any of this helps.

Robert


Well, this gives me some hope. I thought if I could find an oil based
enamel it would be thinner but it seems I can only find it in quarts
and like rust oleum, which says for metal substrates only.

I'll try buying some better paint than the home depot stuff and see if
I can get something to work.

Interesting you say "cap" but Graco sells a needle and an insert. The
cap is reused but I assume it is the same, the orifice is in the
threaded insert. I got the biggest one they say my gun will push. The
next bigger turbine will push the biggest but maybe thinning will
help.

Yes, I was at about 8 inches. I think I will try much less material
and slow down or do more passes to let it build.
  #10  
Old May 27th 11, 04:46 AM posted to rec.woodworking
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Posts: 2,615
Default Spraying Latex with HVLP

On May 26, 6:43*pm, "SonomaProducts.com" wrote:

Well, this gives me some hope. I thought if I could find an oil based
enamel it would be thinner but it seems I can only find it in quarts
and like rust oleum, which says for metal substrates only.

I'll try buying some better paint than the home depot stuff and see if
I can get something to work.


I would urge you to burn $35 - $40 and buy the best enamel you can get
your hands on (really, how much is your paint cost per project?) and
then sit down with a tablet and write down temperatures, a guess at
humidity, the amount of thinning, and the pressure you shoot at.
Before found a gauge I liked, I used to screw my pressure all the way
down to closed, and simply count the revolutions I used to open it. I
took a file and cut a groove in the knob when it was straight up so I
would have a reference. It worked well, but a gauge is better.

Interesting you say "cap" but Graco sells a needle and an insert. The
cap is reused but I assume it is the same, the orifice is in the
threaded insert. I got the biggest one they say my gun will push. The
next bigger turbine will push the biggest but maybe thinning will
help.


With most sprayers, a cap is part of the system. If you buy within
certain sizes, one cap will take care of different sized fluid
needles. So when you buy from different manufacturers, they think
differently; some say a fluid needle/opening will effectively use the
same sized air cap, which will blow out the same pattern from the same
holes. You adjust your finish from there.

Others think that using a 1mm needle size (the one I use for dyes)
requires a different air cap than the one you would use for latex,
typically a 1.7 to 1.6 mm fluid size. Different air caps not only
handle different amounts of air, but they also shoot different
patterns of air into the fluid stream. Since I have a Fuji, I tend to
call them air caps as they only sell a few needle sizes and they all
come with different caps.

Yes, I was at about 8 inches. I think I will try much less material
and slow down or do more passes to let it build.


I actually had to resort to a spacer stick to make sure I was spraying
at the correct distance. I would spray for a bit, then the gun would
move back to about 10" or so, which was great for my high pressure
stuff. Or even to 12". I tend to adjust the distance of the gun
based on the amount and look of the coating on the surface, which is
not the way to shoot HVLP.

I hope you post a follow up.

Robert
 




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