At My Wits End

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PostPosted: Sun May 20, 2018 9:15 am
Hi All
First time posting here and it’s a long one.
I make solid body electric guitars.
I started spray painting them 2 years ago.
I use the Fuji Mini Mite 3 with the HVLP T75G gun using a 1.3 air cap.
I use Cromax 2K urethanes: primer/filler, base and clear.
My guitar bodies are made of Douglas Fir. After final sanding and then cleaning with mineral spirits I spray them with Prep-All, and then just before painting I use a tack cloth on them.
I follow the 4:1 or 1:1 ratios and I add a couple cap fulls of slow reducer. I use an 80 - 90 degree activator and my spray booth is usually 60’s to 70 degrees. The main reasons here for my reducer/activator choices is to allow for a longer set up/leveling time. I spray close, approximately 4 inches away. This is to avoid drying droplets before they land on the guitar body. I try to start with a fog coat and then make the next coats more wet.
I have experimented with all of the above in various forms. The above gives me the best results to date. So what’s my issue I am trying to get on with here?
ORANGE PEEL!
I am primarily talking about OP in the last steps of painting, meaning clear coating.
No matter what I do I cannot get away from it. If I run out the **** fluid control nob so that it’s spraying as wet as can be, the clear will still have OP in it, (plus runs).
This is what frustrates me. To get rid of orange peel I must perform lots of sanding. Fine, I don’t mind the work, but every time I try to sand out the OP I always sand through. I have found it impossible not to. (I have tried many different sanding methods, the latest being using Micro-Mesh pads.) My theory on my sanding through is that it’s because of the first layer of clear. No matter whether I spray the first layer as a fog coat or a wet coat, the first layer will always have OP in it. Since 2K doesn’t act like nitrocellulose and melt the previous layer, I believe the next coats of clear just follow along with the previous coat’s OP hills and valleys, in addition to adding their own OP. So in other words. I must always completely sand off all additional layers of clear to get to the first clear coat because there’s OP there. Getting rid of the OP in the first coat translates to sanding through and having no clear left.
So what do I do?
I have been wanting/needing to start selling my guitars for a while now but I cannot get past my painting issues, and yes, they need to be 100% OP free.
Is the bottom line that I just cannot get an OP free coat down with a 3 turbine HVLP gun?
I believe continuing on, still experimenting, will begin to put me into the realm of insanity.
Please help.

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PostPosted: Sun May 20, 2018 3:47 pm
Can I assume that the Cromax clear you are using is a very high solids clear? If it is, your 3 stage indeed may not be up to the task of laying it down the way you want it. You always figure about 2 psi max per turbine stage so that puts you at about 6 psi at the gun tip. If your solids are up over 40% I could easily see you getting orange peel. Have you ever considered switching to a dedicated wood finishing system? I would recommend a high build hybridized wood finish like Hood's Magnashield. Magnashield contains polyurethane, melamine (think Formica), and some lacquer and can be laid down like glass on wood. Their system still uses different speeds of thinners, retarders, etc., so you can really tailor it to your turbine. Magnashield is even available in black or white which can allow you to create your own colors as needed. Your only other alternative would be to find a lower solids clear similar to the old PPG Omni 161 ( I haven't seen this around lately) which would work with your current turbine.
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PostPosted: Sun May 20, 2018 3:55 pm
Hi Darrel
Thanks for your reply.
Would this wood finish be as strong as the 2K urethane?
I’m reading other posts on here whereby you have commented about the fact that the auto paints are not designed for turbine systems because of the warm air. I’ve never done the ice bucket approach as most of my painting is out in my barn in freezing cold. The last six feet of hose is inside my painting booth at the 60 to 70 degrees. I figured the outside ambient temp in the barn helped chill the hot air.

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PostPosted: Sun May 20, 2018 9:38 pm
Turbine temps. are more of a problem with older turbine designs. Sounds like you are setup okay. I did hit you back with a pm concerning your other questions.
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PostPosted: Sun May 20, 2018 10:36 pm
I too have a Fuji 3-stage, and have found there's two things to watch out for when using turbines. Darrell touched on one, air temperature. The other is viscosity. The recommended mix you're using might be too thick for the turbine. Try using the viscosity cup that came with the Fuji and adjust accordingly. I think you'll find that adding reducer will help to lower the orange peel. Much of the reducer evaporates before the atomized mix hits the surface, because of the high turbine air temps...
"If you can't move it, paint it." - U.S. Army



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PostPosted: Mon May 21, 2018 5:00 am
Hi NightTrain
Thanks for your reply.
I do add a slow reducer. Not too much though as I don’t ant to mess too much with the manufacturers recommendations, and/or weaken the product.

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PostPosted: Mon May 21, 2018 8:31 am
And again.... what Nightrain is talking about there is true. Although you may "add" more reducer (yes, even more than is recommended) it will NOT make it to the surface because the warm air drives it off before it can even hit the surface. It does, however keep those droplets in their fluid state longer so they link up for proper flow out. This obviously does make the wet film build a little less. An answer to that would be to do the normal recommended coats, let that cure until the next recoat window, sand level, then do one final flow coat.
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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