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Join Date: Mar 2004
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Still Painting - Help

Okay so I finally got the paint matched (Gemini Grey). I did a 1st coat and wet sanded it back to do a second but the finish is ending up rough like primer. I think its not going on wet enough. I'm using a gravity fed gun and reckon its not up to doing a panel the size of the door (1.2mm HVLP). Will a bigger gun syphon fed sort the prob or is the nozzle to small. Help! (ps using cellulose primer-base-clear all 1K)

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1991 944 Turbo
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2008 Mini Cooper
Old 09-27-2004, 01:40 PM
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What pressure are you setting at the inlet on the gun? Most of them have the pressure stamped somewhere on the handle. Even though they spray around 10psi at the nozzle, you still need to set the inlet pressure at somewhere between 40-60 psi.
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Kurt V
No more Porsches, but a revolving number of motorcycles.
Old 09-27-2004, 01:56 PM
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Hmm the only control it has is a single knob at the back grip adjusting seems to increase/decrease paint output. (its currently almost fully open). I'm using this one:

Spray Gun
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Old 09-27-2004, 02:11 PM
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What size compressor you using? Is the gun one that "converts" from high to low pressure or do you have the "proper" lo pressure-high volume compressor?

Experience over the years with various paints has taught me there are a number of reasons (if I read you correctly) for a nubby finish. Too far from the panel, too thick, pressure or volume dropping off,a number of other things. Let me know your gun outlet pressure, type, and compressor capacity
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Old 09-27-2004, 02:12 PM
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Compressor spec - 1.5hp, 25L, 8cfm ........the gun is the one I was sold with the compressor just asked for what was best - obviously a mistake! Don't think it converts (hi-lo) neither does the compressor so thats probably the prob. What can I buy that will work okay with that compressor - would the one below be more suitable? (is gravity or suction fed better?) Nozzel size 1.2, 1.4....? thanks for your help most appreciated

spray gun 2
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Old 09-27-2004, 02:35 PM
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Strath, what do you have the compressor pressure going to the gun set at? That is what I am talking about.
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Old 09-27-2004, 03:11 PM
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sorry - my mistake its set at 1.5 out of 10 on the dial can remember how many psi that is. (the guy at the shop recommended this position for the gun I currently have)
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Old 09-27-2004, 04:15 PM
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1.5? Is that bar, psi or some arbitrary number on a dial on the compressor. You need to have a gauge on the compressor, preferably one that connects on the end of the spray gun that shows an accurate psi or bar. If it is 1.5 bar that is way too low. You need to be at around 3-4 bar or higher. Here is a thread I posted on the 911 board when I sprayed the ducktail on my 911. Perhaps it will help you out:
Painting the Ducktail
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Old 09-27-2004, 07:16 PM
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Without a gauge you are only guessing. Try the gun on a test piece of material at various settings and see which one works best. Also, the "mix" of finish to reducer is very important. Too little reducer and the gun will "spit", resulting in the nubby finish.

Also the grit of the paper you are using and the amount of water is important. Keep the water clear, work your way up to about a 15 micron paper and final polishing with Mirka or equivalent will result in an awsome finish.
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Old 09-27-2004, 08:20 PM
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Hi did a few tests with the gun tonight from 40-70psi but made very little difference (appart from getting worse and providing a very small fan pattern) will get a better gun tomorrow with more adjustment and try again.

Kurt thats a good write-up on the spraying the ducktail. What is the spec of your gun ie nozzle size/average cfm.

"Also, the "mix" of finish to reducer is very important"
-
The cellulose I am using is 1k / 1 pack so just needs thinned and the clearcoat is RFU - straight from the gun.

From what I have seen lot of people are using 2k / 2 pack in the US, everyone I know is very nervous about it (hence why I used 1 pack - its bad enough) as it is highly toxic and should only be done in a booth/with air fed mask- . Is it a different type or is everyone here over cautious?
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Old 09-28-2004, 01:58 PM
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Em cellulose basecoat - then clearcoat on top. don't think its a prob with the thinning as I am doing it exactly as per the manu/auto shop guidelines. Not familiar with enamel as a metallic maybe its just different termanology as over here enamels are solid colours - don't think many places mix/sell metallic colour topcoat (ie needs no clearcoat) as it is nigh on impossible to get an even finish - as soon as you buff/colours and its apperance changes- as far as I know.
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Old 09-28-2004, 02:40 PM
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I am using a 1.8 mm tip. Here is where you can find the specifics on the gun: Devilbiss Finish Line Spray Gun

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Old 09-28-2004, 06:02 PM
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