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Avoiding "Stripes" in a Flat Finish
Question
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Get a 2' x 4' test panel and use a wet film thickness gauge and apply the product 3-5 mils wet. Ensure that you lap the gun 50% on each pass. Also start at the far end and work your way toward the fan. If this is already what you do, then I'm not sure what the problem might be other than bad finish or the surface isn't sealed properly.
From contributor J: A quick method to see if your pattern is uneven is to spray your gun with a horizontal pattern at a vertical surface. Don't move the gun. If it runs more on the outside of your pattern, it's uneven. You might need a new tip, or less fluid pressure. From contributor C: Uneven spraying is the problem you are dealing with. I would box spray it. Dead flat is a bit tricky. Stir just before you spray, coat very thinly, move fast, box coat (from two, three, or four directions). That ought to bring you home. You are either getting some strips too wet or too dry. Theoretically it can be done with passes all from the same direction, but practically speaking it is harder than it needs to be when done that way. From contributor G: How about thinning 5% and adding some retarder to your mix? From contributor T: Try putting on another coat. That should even it out. From contributor L: I have to agree with the overlapping of finish. In an airless, if your pattern is off even a little bit, it'll streak. From contributor P: Spraying wet on wet at 90 degrees (box coat) works for me. I've tried adding thinner and/or retarder, spraying heavy or light coats, holding the gun off the surface more than normal, making sure to keep the gun perpendicular to the surface, and overlapping each pass as much as 80%, all without getting consistently good results. It doesn't get better with added coats. Watch out for your total dry film thickness. Sand the existing coat back fairly aggressively before recoating - especially since you will be essentially applying two coats when you box coat.
From contributor T: Just a thought... Has anyone tried spraying in one direction only instead of the usual back and forth pattern? From contributor M: Maybe this is too obvious, but have you checked all the air nozzle openings? Are they perfectly clean? Just a small piece of dried finish will effect the spray pattern dramatically. Also the fluid nozzle should be cleaned, and make sure there is no dried finish in there either. Check the spray pattern on a piece of cardboard without moving the gun. Is the shape a perfect oval? If it is lopsided, there is a problem with the tip. From the original questioner: Thanks. I had him change out the tip because it was a little heavy on the outsides of the pattern. They came out a little better. One is consistently cloudy looking all the way through now. But thank you. Does anyone use different finishes for that dead flat look? We use SW Kemvar LF and that is all we have used ever. Would you like to add information to this article? Interested in writing or submitting an article? Have a question about this article? Have you reviewed the related Knowledge Base areas below? 
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