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| Spraying KTM-9 http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=12676 |
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| Author: | dubell [ Mon Jul 02, 2007 12:16 pm ] |
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It's been a while since I have sprayed. Last time was 10 years ago using Minwax water base finish. I played around all night and I am having trouble spraying a nice finish. The Rosewood Back and Cedar top are giving the most trouble. The finish has a "sandy" look and touch to it. I am spraying with a Devilbiss HVLP touchup gun....What in the world am I doing wrong? |
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| Author: | KenH [ Mon Jul 02, 2007 12:57 pm ] |
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sounds like overspray to me. If I am not mistaken, the KTM-9 is supposed to be brushed on, but I'm like you and would have to try spraying it on. The finish you seek should be easy to get using some rubbing compound on it after the finish has dried. I have had good luck using rubbing compund (meant for car finishes) and then Maguiars PlastX plastic refinishing compound for the final finish buffing. I do all of my buffing by hand. It is fairly easy to do. |
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| Author: | Dean [ Mon Jul 02, 2007 1:07 pm ] |
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hope this helps. Pebbling .-This fault, in which the material is deposited on the surface too dry, as a kind of dust, is usually the result of spraying at too high an air pressure which causes the solvents in the finish to evaporate from the atomised particles before the latter reach the surface. Orange-peeling.--.---This may be due to the material itself not possessing sufficient flow or to the use of unsuitable thinners. Again, it may be caused by the use of too low an air pressure in relation to the viscosity of the material, with the result that atomisation is imperfect. dean |
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| Author: | Tim McKnight [ Mon Jul 02, 2007 1:12 pm ] |
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You may be too far away givig the atomized finish a chance to dry before it hits the surface. Your travel speed can be too fast. You need to spray WET even coats with a 50% overlap. It is important to use a dessicant filter especially when shooting water borne finishes or you can get a blue-ish color cast. |
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| Author: | dubell [ Mon Jul 02, 2007 1:20 pm ] |
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I have a feeling the finish is drying before it hits the guitar. I did try moving the gun closer and turned the pressure down to 60 psi. This helped, but then it looked like I was getting orance peel. Do you think I should thin the KTM-9t with denatured alcohol? |
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| Author: | Tim McKnight [ Mon Jul 02, 2007 1:51 pm ] |
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If you are using a turbine as a source of air pressure then this could dry the finish before it is applied to the surface because the air temperature is often very warm. |
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| Author: | Dean [ Mon Jul 02, 2007 3:00 pm ] |
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Your pressure for hvlp should only be 4-12 lbs. Put a small regulator on the gun. pick one up at the HD. You should have a viscosity cup or viscosity drip stick. check at your better paint stores where quality guns are sold. they will tell you the standard viscosity for the tip you are using. you may need to change the needle and tip size. Dean |
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| Author: | Steve Saville [ Mon Jul 02, 2007 3:53 pm ] |
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Check your nozzle size, it might be too small. If you touch up gun is under 1.0mm, that might be the problem. I tried a water based product with a 0.8 mm and got exactly what you are describing. If you can't get it to run somewhat easily, then you aren't putting out enough finish. |
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| Author: | SniderMike [ Mon Jul 02, 2007 5:20 pm ] |
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I've just gotten a lot of experience (because of my mistakes) spraying Target Coatings USL waterbase lacquer, which I assume is pretty similar to KTM9. I would say your psi should be 30-40 coming into the gun if you are using a standard air compressor, and you should be using no less than a 1mm tip like Steve said. I get good results spraying about 8" away from the guitar. I would defninetly not thin with DA. Use water, unless you have retarder. I know Target has a retarder for USL, not sure about ktm. |
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