I done a bit of finishing (cabinets) in the past. I used high
pressure guns and Nitro lacquer. The combination produced very nice
finishes with little or no effort or problems. Theproblem was that my
wife always got sick from the vapors.
I decided to switch to a Sharpe Cobalt HVLP gun (1.5 mm ) a few few
years ago with both Kem Aqua and/or Hydrocote Resisthane Plus water
borne lacquer. I have tried everything and have yet to produce a
surface comparable the Nitro ... operation.
I am currently working on a good quality birch ply cabinet.
My method of setting up the gun is to put about 35-40 PSI on the
compressor and change it until I measure a sustainable 10 PSI air
pressure at the exit of the gun's nozzle. The Hydrocote seems to take
20 seconds on a Ford Cup. The instructions say I can add up to 1/2
ounce of water in a 16 ounce cup (does not seem to be enough to have
any effect). I open up the fluid flow on the gun all the way and
thenback it off 2 turns - which prevents drips and runs on a vertical
surface. I get a nice spread of very well atomized lacquer. However,
the finish always ends up with a very fine orange peel surface instead
of a smooth continuous sheet of lacquer.
I have tried making two passes in a single coat; I tried opening up
the gun; I tried closing it down. Temperature is about 75-80 degrees
and not too humid - no blushing. I never seem to get the fine finish
I want. Today, it is a lot of sanding and rub out - and take whatever
is the result!
Anybody out there have a clue what's wrong and how to fix it?
It is hard to be a high pressure application of nitro lacquer. If I
were you I would consider going back to it and send your dear wife to
visit her sister while you do it. The vapors are no joke; but with
the right application technique you can mitigate them a great deal.
I am familiar with the Kem Aqua, but not the Hydrocote. Kem Aqua is a
good product, but I have never had it come out as good in the end as a
quality NC coating. Additionally, some of the waterborne products
really need a good sanding sealer under them to get a good finish, so
if you left that out, you might be in trouble there.
I would check the manufacturer's (Sherwin Williams Phone:
1-800-524-5979) and see what they say about the nozzle size on the gun
you are using. Most manufacturers indicate a nozzle size of somewhere
between 1.2mm and 1.4mm for lacquers. They can set you straight on
the tip size and the correct psi to spray. Remember though, they are
giving you general guidelines.
Compressor indicators are notoriously inaccurate for finishing. You
need to get a good line regulator and put it under the gun. This will
allow you to get more accurate readings at the gun, and you can open
your compressor up to 100 psi.
This will allow you longer, more consistent spray times without your
compressor cycling constantly to replenish the tank.
It may not. Trial and error is the only way to find out exactly how
that material responds to your setup. The finishes are so forgiving,
would thin and spray several different test setups with different
solutions to find what works.
Remember that you must take in temperature, humidity, etc. when
On your mechanical setup, thin with distilled water. Also, make sure
you have a oil/water separator under the gun (not at the compressor)
unless you have a short hose. Don't use the hose that you power your
pneumatic tools with, either. A lot of crap builds in those hoses
over a period of time.
Put a reference mark on the adjustment knob and on the gun body. Use
that mark to fine tune the spray pattern as you adjust your mixture.
Write down the settings and the mixtures for future reference, along
with the temp and humidity.
IME, with HVLP guns, the #1 reason for orange peel (barring
contamination) is that the material isn't thinned enough. Try
thinning your material more and putting on a thinner coat. Working
within the product's guidelines I think you can recoat the KA stuff in
something like 30 - 45 minutes (check that, though). That means you
can build your finish rapidly.
Don't make two passes with lacquer unless you know what you are
doing. It will build the product too thick, and will not allow proper
outgassing. This can cause your orange peel as well.
If it were me, after I got my mechanical stuff in order (gun
regulator, upped pressure at the compressor, new hose, separator) I
would thin the material about 25 percent and start there. If you are
shooting a clear formulation, there is nothing to desegregate, so thin
away. Forget measuring the output of the gun. A CAS gun will do
that for you. Get your gun pressure up to about 50 lbs, and open the
fluid slowly until you get the spray you want. You may have to go up
or down on the pressure and make a couple of different formulas when
thinning, but that should get you on your way.
Remember.... practice on scrap, not on your project.
Sorry I didn't read all of nails post, to many words, so I might
repeat. Also, just have general input because my one disaster with WB
material scared me away from it.
However, with nitrocellulose I found a cross hatch pattern is best. I
suppose this is similar with any sprayed finish.
Set up your flow so that one set of passes is not quite enough
material laid down. Then on every surface spray it twice. Once right
to left. Then immediatly top to bottom. The application of two
complete coats sprayed from perpendicular directions gives great
coverage and the amount of material laydown should be just enough so
the combination of two coats provides enough to flow outthe surface.
I would also look to see if you can something like flowtrol for WB
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