Graininess in base coat

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PostPosted: Tue Aug 27, 2019 5:25 pm
Hi All
I am getting that sandy feel to my lacquer base coat that suggests I am spraying with too much pressure.
FYI, I used to paint with a Fuji Minimite 3, as described in one of my earlier posts, but I upgraded. (To me now, turbines are for painting houses.)
I bought an Iwata LPH80 124G minigun. (I make guitars so nothing big needed.)
I got the 2.5H/21gallon AC from HarborFreight.
I installed copper piping in a "lawn mower" fashion and lots of dirt, water and oil removers in-line. The gun requires only 14 PSI/1 bar. I set the output PSI on the AC at 40 PSI and then the input regulator at the gun to 1 bar. If I change any gun settings then I recheck my pressure and tweak back to 1 bar if needed. My distance to the guitar is about the width of my hand. I use the wall-of-air method to determine the distance. When I spray I notice I have almost zero blow back or over-spray. The spray looks so much more atomized than what my Fuji ever could do and I have a finish now that has very small OP. However, I am getting some graininess and I don't know why as I am spraying at the proper pressure. So, my question is...
Can I procede to clear coating now?
I'm thinking that once I start spraying clear that the clear coats will melt the grain of the base coats and thus do away with the graininess. I figure I can just wet sand out any graininess in my clear coats if that occurs.
I'm trying to avoid wet sanding the base coat.
PS: I love this new rig. I really feel like I am finally spraying with professional equipment now. The atomization is awesome. It blows the turbine gun away. Also, my AC is totally adequate for this gun.
Any and all replies are greatly appreciated.
Maplehead



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PostPosted: Tue Aug 27, 2019 10:07 pm
you say lacquer base is it truly lacquer and not modern base coat. that 14 psi at the gun is just a recommendation you can go up or down it depends on the viscosity of your paint. the graininess is it like its slightly wrinkled or are we talking orange peel ?
Jay D.
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PostPosted: Wed Aug 28, 2019 7:51 am
The lacquer is Mohawk Classic Instrument Lacquer. Pic shows contents.
I don't see any wrinkling. There is orange peel but much smaller in size than I am used to.
Do you think if I sprayed just lacquer thinner over the base that it would melt in and level it somewhat?
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PostPosted: Wed Aug 28, 2019 8:51 am
Okay....blew up the pic.s and ran some of our filters over it. I see two things....small consistent orange peel and what looks like "solids" (pigments/fillers) bits and pieces not linking to form a continuous dry film. That is the "grainy" problem. What are your shop temps. like? What are the temp.s of your surfaces. Are you thinning this at all or using retarder with it? Could be a problem with that color/mix as well. Mohawk blends in huge batches and stuff can set in inventory for quite some time especially colors that aren't that popular. Oh, and did you blend it with a stick or a paint shaker? I have an air shaker that we use on all their bulk pigmented stuff (quarts, gallons).
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PostPosted: Wed Aug 28, 2019 9:54 am
Darrel is on the right track I looks like its to dry, to fast of reducer or under reduced. post all your materials and how you mixed so we can see what your doing.
Jay D.
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PostPosted: Wed Aug 28, 2019 1:21 pm
I use the colortone lacquer pigments from Stewmac and I mix with a metal stirrer.
I used no reducer, just the lacquer straight out of the can and the pigment. The temps have been around 70 here and the humidity was around 50.
I set my fluid to about 2.5 turns from closed as Iwata recommends spraying as low fluid as possible.



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PostPosted: Wed Aug 28, 2019 3:59 pm
there is really no way that they can premix lacquer so that it will spray good at 55 deg. and 70 or even 80 deg.. at higher temps it going to dry to fast. I would try and thin it some with a real slow lacquer thinner. lacquer needs to go on fairly wet and at low gun psi. if you have enough build you can sand the base as long as its a solid color then clear. you'll need to sand it smooth, get all the texture off. you would be much better if you could buy the color unmixed.
Jay D.
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PostPosted: Wed Aug 28, 2019 4:33 pm
Yeah, everything Jay said there and...... if you are indeed making your own color coat here I think a shaker mixer is needed to get that pigment blended in so it's completely broken up for dispersion. If that was a powder or liquid pigment to clear mix made by us in-shop I would be stirring it in for about 5 minutes and putting it on my shaker for up to 15 minutes. If after 15 minutes you can squeeze some of the color between your fingers and see micro sized mashed particles it needs more mixing. A mini gun is definitely going to be more prone to unblended particles since the orfice size is smaller.
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PostPosted: Wed Aug 28, 2019 4:40 pm
Oy!
Thanks for the replies gentlemen.
It seems like every step forward I make I find out another thing I need to do or to purchase. Now a paint shaker? Ugh!

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PostPosted: Wed Aug 28, 2019 10:46 pm
It's been a few years back but all the hardware and paint stores had to switch over to totally enclosed paint shakers so a lot of the electric ones they used ended up for sale. I've seen them now and then on Craigslist, ebay, etc. going in the $25 to $100 range. Mine is an explosion proof air driven model. They are generally cheaper when new but can be "air hogs" as far as cfm when operating.
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