# Spray finish streaking...



## Fram1024 (Jan 8, 2011)

I'm having an issue w/ my spray finish (topcoats) on the tops of my projects. I keep getting what appears to be a "streaking" effect (the edges of the spray pattern seem to be dull). It's only an issue on my bigger surfaced projects were I need to make multiple passes to cover the top surface. 

I'm spraying SW Cab-Acrylic Lacquer w/ a Fuji Mini-mite 3 w/ the gravity feed gun. I've gone through the process of adjusting the width of the spray pattern & the volume of the material I spray, but I still seem to be fighting the problem.....and its driving me nuts!!!

Any suggestions would be appreciated...


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## Tony B (Jul 30, 2008)

*Spray Technique*

The way to avoid overspray (dry spray) is to keep the entire surface wet all the time you are spraying. The idea is not to flood the surface but just the opposite. Spray on a thin tack coat all the way around the edge. Then go back around the edge with a full coat and immediately continue on with a quick coat on top. The quick coat on top should be a wet coat but still fairly thin. Without stopping, hit the edge again with a full coat and lay down a good wet coat on the top. Then moving quickly, criss-croos the direction of spraying the top, keeping everything wet, but not flooded.
This can be tiring on the arms, but the idea is to not stop until done. 
There are variations from the above that can only be determined by you and the size of the piece you are working. With pre-cat, you only want a final dry film thickness of about 4 mils. The above technique will get you close to that. Most pre-cat manufacturers recommend only one or two coats. 
I am not familiar with the Fuji system, but generally most hvlp systems require a slower movement than with conventional spray. 
Anyway, the general idea is to keep everything wet until you are finished with that coat and at the same time not get it too thick


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## RetiredLE (Jan 20, 2011)

The key is to hold the spray pattern before and after the material being sprayed. 

In other words, activate the gun and begin applying material just prior to the surface and end it just after - whether laterally or vertically. You are essentially spraying material into thin air.

Also, keep the gun at a 90 degree angle to the surface throughout the sweep.


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## cabinetman (Jul 5, 2007)

The dry edge could be from a weak output at the edges of the pattern. Try changing the pattern. It could be the distance from the work or the speed of your making passes, or fluid to air ratio. Getting this combination right comes with practice. Use a retarder, as it will allow the application to stay wet long enough for the next pass. In thinning the lacquer, you could use a "slower" lacquer thinner. SW carries it.

You might experiment with waterbase polyurethane. Lacquer used to be my finish of choice. I don't use it anymore in favor of WB polyurethane. Many pluses, such as no blushing, good coverage, durable as lacquer (IMO), easy clean up, less toxic, and dries almost as fast.












 







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## Blur (Feb 1, 2011)

Interesting to hear Cabinet man! Do you run into issues with the WB Poly raising the grain, and if so how do you deal with it? I'm curious as I'm sure you don't have any spare time to waste on extra steps on a project. Thanks for this really interesting info, so far I've generally avoided WB finishes because of some of the issues with them. Sounds like I might need to give them a second look. I'd love to hear anything else you have to say on the subject.


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## cabinetman (Jul 5, 2007)

Blur said:


> Interesting to hear Cabinet man! Do you run into issues with the WB Poly raising the grain, and if so how do you deal with it? I'm curious as I'm sure you don't have any spare time to waste on extra steps on a project. Thanks for this really interesting info, so far I've generally avoided WB finishes because of some of the issues with them. Sounds like I might need to give them a second look. I'd love to hear anything else you have to say on the subject.


I don't use any sealer, and I don't pre-wet the wood to raise the grain and sand it down. To tell ya the truth, I don't see it as a problem. Even with Red Oak or Mahogany, it's hardly noticeable. After the first few applications, I'll lightly sand with 320x. With the finishing regimen, whatever grain that gets raised, gets sanded down between applications.

I don't sand the first few coats, as I don't want to take off any color if there's a stain. I think the hoopla created by forums has made it a bigger deal than it is.












 







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## Blur (Feb 1, 2011)

Ok, that makes sense. You're basically burying the grain in the build of the film then leveling the finish so any variation from the raised grain is eliminated. Cool. If you don't mind one more question, how do you clean up your gun after using water base? After using solvent based finishes, I just spray some of the thinner for a bit to clean out the gun (probably not the "officially right" way but it works fine. I can tell you painters in the autobody industry do it this way all the time anyhow...). Do you have to strip down the gun and clean out the individual parts or is there an easier way with WB? I really appreciate the info!


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## Leo G (Oct 16, 2006)

Add a retarder to your lacquer. This will slow the drying down and keep it wet longer.


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