Hi All
So I've been trying to paint my solid guitar bodies now for about four or so years. I started out with single stage, moved to 2K polyurethane and I'm now using NC lacquer. My latest process is to sand the douglas fir with 180 grit. I then apply three to four AquaCoat coats to fill any anomolies and I sand in between each coat, usally with 320 grit. I then move to three coats of vinyl sealer lacquer and I sand after the last coat with 320 grit. So, bottom like here is that I feel the body is well filled, sealed and sanded smooth and ready for some color. Here's the thing. Without fail, the sides of the guitar always come out perfect. And I mean perfectly smooth with not a micron of orange peel, However, it's ALWAYS the front and back of the body that has the issues, (and the rounded areas), whether that be sandy texture from dry spray or orange peel. So my obvious question here is... Why? Why does the side of the guitar take the spraying perfectly? The only thing I can think of is that the fan envelopes the entire side as I go by. Maybe if I had a twenty inch fan and could make one pass over the front and one pass over the back, covering the front and back completely in onepass then things would be different. I have no idea. Your thoughts?

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My guess is that you are changing speeds of how you move your gun. The body coats also look dry to me. But I'm also suspicious about all the layers under the NC lacquer. I'm certain I would not start with a water based primer under those hot solvent based materials. I assume AquaCoat is water based with that name. But I would not start with Doug Fir either. Isn't it really tough to properly sand and not get a ripple from the early to late grain hardness difference?

Yes, it's a real PITA. I look for older, very tight lines and that greatly helps. The Doug Fir though is a great body and neck wood. It's very light but very stiff and it also has a nice tone to it when knocked. I haven't seen an issue yet with the AquaCoat under the vinyl sealer, but that doesn't mean there isn't one. As far as speed goes, it feels to me that I am going the same speed. I've sprayed about forty bodies now and the same thing always happens, leading me to believe that it's something else.

Sounds to me like your finish is drying to fast, it's the overspray from the previous
pass that's not melting in.
Slow the dry time down with a slower
thinner and maybe even retarder.

Hi Jim
But why would the sides go on so good, without OP?

Once again you're not getting what we are saying
The spray gun you are using is not meant to use for large surface
The edge looks good because that's the best you're going to get with that spray gun
You need to invest in a better spray equipment

With all due respect, most of my spraying time has been with the Fuji MiniMite 3 and its T75G gun, which is a regular sized gun. I used the 1.3 tip. I got the exact same results. Sides awesome, front and back not.

Another reason could be the fan pattern and not enough overlap on the faces. You could be getting a wetter coat on the sides if the center of the fan is wet, and a poor finish on the faces with the pattern too wide, dry edges, and not enough overlap. With all your questions on that gun, you should be running a ton of practice pieces. Playing with fluid viscosities, pressures, and fan patterns. Looks like you have a lot to learn with your equipment. Even just spraying water on cardboard will tell you a lot!

Maplehead
Sorry but in your other post you mentioned that you are using a minigun from Iwata
Now you're saying you're using a Fuji turbine
With a 1.3 nozzle?

So here what I think
Don't use a small touch up gun for large surface
As far as your Fuji,I would use a larger nozzle like 1.5 maybe 1.7
Maybe you're not setting the gun properly or going too fast on the larger area
Are you overlapping by 50%?
I used to have a turbine system and never liked it
I was getting poor finish and some dry spray
I think it has to do with the hot air coming from the turbine unit
Drying the material too fast at the air cap maybe?

Hi Mastercabman
No, I'm saying I used to use the Fuji, a standard sized gun than the Iwata, and that I got the same exact results then as I am now. (Realize I am talking about the sides coming out great while the front and back do not.) I purchased the Iwata for three reasons: One, it can output more PSI and my many hundreds of hours of research over the years suggested that PSI is the number one thing in regards with proper atomization. The Fuji at best gets to about 6.5 PSI at the tip. HVLP needs 10. Two, like you said, the dry air. It's super hard to get away from OP with that dry air on a turbine. Three, the Iwata required less CFM and PSI at the gun. (14PSI going in to get 10PSI at the tip.) Because money is tight and I cannot afford a $1000 60 gallon compressor, which runs at 220 volts meaning I'd also need 220 run out to my barn, I purchased a 125PSI/21 gallon compressor from HarborFreight for about $150. That compressor gives me all that I need for a single coat using the Iwata. I recharge the compressor before the second coat, (an hour later).
Regarding capability, I researched the use of the gun and owners love it and say it's top quality. The Gunman on Youtube, a highly respected auto painter, used it on a panel that's many times bigger than my guitar body. Motorcycle shops use the minigun for spraying gas tanks and they love the results. Gas tanks are bigger than my guitar body. The front and back sides of the body are each approximately 1 square foot in area. In the spray painting world that's got to be pretty small. Basically, if you are reading this post on an iPad Pro, that flat screen is about the size area I am spraying.
With regards to practice, I hear you all, but realize in the last four years I have been spraying the exact same item over and over again, using different equipment and different pressures, mixtures and whatever else everyone writes about and suggests. I have to imagine that has accumilated to some experience. Outside of that, time and money keeps me from a hundred practice takes. Although I agree with you all, I still need to do it.
Lastly, this particular thread is not so much about quality of spray, (dry or OP or runs or whatever). It's just focused on one thing, why do the sides always come out very good while the front and back have the issues?

1. Nitro flashes off very fast without having some retarder added. I'd suggest using 5% butyl cellosolve with your mixture. Nitro tends to be fairly viscous depending on the brand so it most likely needs be be reduced 20% as well.
2. I'm going out on a limb here because I've sprayed many many guitar bodies and I'm certain you are getting more wet mils on the edges than you face and back.... Naturally you run that pattern around and around to wet that profile.... I'm guessing your not laying enough material fast enough down because your material is flashing too fast or your gun cannot handle the volume needed to go down fast enough.

Do you spray your sides last or at the beginning? If at the end the blow by to front and back could be not keeping a wet edge open long enough. The over spray is wet but the flat surface of the front and back have already started the drying process.

I have a small paint booth, 4'x4'x7' with a really good exaust fan. I made a jig to hold the body so that I can turn it. I start with the body laying the front horizontally so that the sides are facing me. I start spraying at the bottom section of the side, (where the strap holder would be), and I move up to the top horn. Then I spray the neck joint section facing me. Next I turn the guitar over so that the back side of the guitar is now facing up. I start spraying the side again from the bottom strap holder area and all the way back to the neck joint section. Next I turn the body so that the front is now vertical and facing me. I start from the top down moving left to right, 50 to 70% overlap. I then do the same thing for the back side. I repeat the above two more times and then I call that one coat and I wait an hour before spraying the next coat.
I don't understand why the sides always come out different than the front and back. However, I am definitely getting it drilled into me here that I need to spray the front and back wetter and faster.

In reading my own reply here the number one difference that stands out between spraying the sides and spraying the front and back, is the overlaps. There is no overlapping with spraying the sides. I wonder if I should reduce my fan size so that it's more concentrated like spraying the sides, and then overlap that. My only worry here is the potential for runs.
BTW, yesterday I added more reducer as so many had suggested me doing that. After spraying over previously painted base, the spray job looked like I wiped the body with a lacquer thinner soaked rag. The wood grain started to show and there were many areas of very thin paint. I've never seen that before. Maybe I reduced over 20%.

" It's just focused on one thing, why do the sides always come out very good while the front and back have the issues"

Because the sides are more narrow than the front and back
Much easier to cover the edges than larger flat surface

There's something you're doing wrong or using the wrong equipment

Well, I'm biting the bullet and I'm going out to buy a couple sheets of MDF. I'll route them into my guitar shape, spray them with vinyl sealer, sand smooth and then spray them in different gun settings and mixtures.

i firmly believe he is pulling way too much air across the face of the guitar ,the side are baffled from the speed of the air going across the guitar and thus not drying out the or flashing off the solvent of his coating, my suggestion is to slow down your fan speed , i think you see a dramatic reduction in your dry spray especially across the larger face of your guitar
good luck
herb j

Hi Herb
I'm not understanding your reply. "Too much air across the face" and "slow down fan speed". There's fan width but not speed. Should I be narrowing the fan width on the front and back? "Too much air across the face". Should I be reducing the PSI when spraying the front and back?

sorry, i mean the exhaust fan motor rpm

let me offer this to see if this might be a solution to your issue, try spraying without your exhaust fan on to see if all the air movement of your exhaust fan is causing all of your dry spray , i.e. flashing off all of your fast solvent to fast so to speak, it is a real fast fix to see if this is your issue, have sense it might be especially with sides of your guitars not having any issues

good luck herb j,

Excellent suggestion Herb..... If he is shooting with a ton of turbulance blowing past the surface that could very well cause a huge issue.... you want a nice rolling pull not a wind storm...

i am betting a quart of mek and binks repair kit lol that this fixes his issue, just my gut feel......lol

Hi Herb
The interesting thing here is that I installed the fan for the sole purpose of assisting me in eliminating dry/overspray spray. Before the fan the coats were sandy. Since installing the fan I no longer have the sandy coats, just some orange peel. I researched online for how many CFM's I'm supposed to have drawing from the booth and the formula is is square area of face, (width x height), and then times that by 50. Now some sites say times it by 100 and others say three times the square area times height. My booth is 4x4x7. So face equals 28 while overal square footage equals 196.
So the above would suggest I work off of 1400, 2800 or 588. Quite the range of suggestions. The fan I have now draws 1720CFM. I no longer have a cloud in front of me but by the third pass I can feel the lacquer hitting my eyes. (Gotta get a mask.) I'll try turning the fan down a little but I don't want to too much as it has really helped in keeping the sandy texture off of the guitar.

That last formula is total square area times 3.

BTW, I just made 14 .5" MDF "guitar bodies" from my template. I guess I'll start practicing soon.

actually it height x width x 100 but sometimes it gets funky by getting into the ldl or lower explosive limit of the atmosphere, the thing i was thinking is that the sides are kind of sheltered from the cross flow of the air going toward the exhaust fan thereby decreasing the possibilty of the early flash off of solvent or dry spray however i get the fact that before the exhaust fan the overspray cloud was depositing some overspray over your work i get it, so maybe slowing down the fan a tad might be the answer , i know it isn't my shop but i love a good mystery so to speak, been doing this stuff for awhile and been thinking about your situation for some time now, hoping we can you a solution, been also thinking what the other fellow been saying about adding a slower solvent to keep the surface open a little longer to help with the peel

I add a cap full of retarder. (I know, I'll start measuring exactly in the future.) I will definitely turn down the exhaust fan next time. Here are pics of my set up. You can see my old Fuji in it. The guitar body is on an arm that mounts to that horizontal pvc pipe.

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A few more pics. I don't use the gauge at the gun anymore. You can see it here, (lower right corner of pic), mounted inside the booth. After that is a 6' hose to the gun. I have a secon, LED light above the inside of the door that's not in picture. The fan in one of the intake windows I no longer run.

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Ok. I'm on board with too much turbulence. Your room is tiny only 112cuft. At 1750cfm you're emptying it in seconds. Replace the window and the door or even the whole back end with mesh filtration. Also I'd raise my exhaust port to work height. I would also think about making a jig to rotate the guitar with a lathe type setup to facilitate horizontal spraying.

my2cts
cheers

Hi Bart
The jig does rotate. Are you saying I should spray the front and back of the guitar body why horizontal? I never do. I always have it vertical, facing me. Also, in my research it seemed bottom exhausting is best. The spray eventually falls anyways. What benefit is it to have the exhaust level with what I am spraying? Lastly, in practicing today I did turn down the exhaust a lot. I don't know if it helped or not. See my odd results on the plywood I sprayed in my other post.

I can't imagine only a cap full of retarder
making a difference.
I usually replace half of my normal thinner
reduction with retarder.
Gives a real nice flow out.
Do the same with my auto painting.

Whenever I'm spraying a fixed shelf unit I always put the bottom shelf up on the last coat. This gives me the best/smoothest overspray free result. If I were spraying a guitar I would spray horizontal so I could wet out the surface as much as possible. Do the bottom first then roll/spin it and do the top or viceversa whichever gave the best finish on the face. The down facing surface is very very resistant to running even with a heavy coat.
As for exhaust height I want as much overspray exhausted as quick as possible. Your setup it's just bouncing off your back wall and you're getting rebound onto your guitar before it makes its way down to the floor. At a minimum you should have some mesh filter material on the wall you're shooting against to absorb your overspray.

my2cts
cheers

you have to play around with the right amount of retarder.then you need to spray beginning with your edges and ending on the face

Your tip is to small, 1.3 tip is for automotive paint and for painting your car.
The smaller area is getting enough finish so it looks ok, the larger area is not getting near enough material. Get a bigger tip at least 1.8 and see if that helps

Maplehead
Did you figure out the problem you're having?

I did tests on MDF that went well but it's just too different an animal. I have to do it on the real thing. Unfortunately the Douglas Fir is pretty expensive so I will not be making test DF pieces to shoot. I'll be spraying a new body by the end of this week so we'll know. Things I am going to be doing: Turning down the exhaust fan so that the draft itself is not drying the sprayed body, putting some mesh or a filter behind the body to prevent bounce back, keeping the gun at its current high pressure setting of 29 PSI into the gun, spraying at 4 to 6 full turns of fluid to get a wetter coat, overlapping more than 50%, will make my 20% reduction 3/4 parts urethane slow reducer and then 1/4 part lacquer retarder. That's about it.