Official Luthiers Forum!

hi every one......at the moment i am spraying with nitro and compressed air and im trying to hone my technique to reduce overspray......what sequence do you guys spray your acoustic guitars in to avoid overspray...i also find holding the gun at an angle helps me get a nice wet coat......

First you must understand that overspray is inevitable and somewhat desirable at times. When you make a pass with the gun you never want to start the spray or end the spray on the work piece. You always want to start off the work piece travel at a constant rate across and beyond it. When you first pull the triger air is the first thing out the nozzel. it takes a fraaction of a second for the finish to be atomised into the air stream. Pulling the trigger and starting the spray right as you approach the surface will cause spits and blow outs, ending the spray on the surface will induce blowouts and sags Ideally you want to start the spray 3”-4” prior to the surface and move the gun in a parallel plane to the surface. Not in an arc or sweeping motion. A sweeping motion produces much more over spray and changes the distance from the tip to the surface in the process.

So to answer your question directly the biggest thing you can do to keep overspray to an ideal minimum other than proper mixture settings is to use proper spray path technique.

Get a high efficiency gun e.g. HVLP.

My first spray I used a high pressure gun and within seconds my shop was filled with overspray. For my second, I went to HVLP and my shop stayed mostly clear to begin with and was cleared out by fan/filter within a few minutes.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Overspray where? You mean like getting overspray on the top/back when you are spraying the sides, or getting overspray all over your walls?

I like to shoot the back first, then sides, then top, althought the order does not matter much. For tops and backs i shoot overlapping coats with the guitar held vertically, then go over it again with overlapping coats horizontally, kind of like a grid. Similar for the sides, i spray lots of little blasts across the sides, then long blasts from tailblock to neckblock. The biggest thing to watch out for with the sides is a dry tailblock area, it is the hardest place to reach with the gun and can be neglected. I am describing spraying a guitar without the neck attached, with a handle screwed to the neckblock. If i am spraying with the neck attached, i do the body as described, then the headstock, then hang it up and shoot the neck shaft.

If the neck is not attached, i like to lay the guitar horizontally while it dries, the top and back self level better that way.

Thats how i do it, and it works well for me, but everybody kind of develops their own routine when it comes to spraying. I dont do anything special to avoid overspray, the finish will burn in to itself if a little bit of spray from the sides gets on the back or whatever.

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Jordan Aceto
Ithaca, NY