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 thinning.
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 someth> I done a bit of finishing (cabinets) in the past. =A0I used high
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