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Spray setup help

skelrad

Well Known Member
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I’m a complete painting novice, so have a few questions following my first priming session today. I'm using Stewart Systems EkoPrime. I had some trouble getting the gun (Devilbiss Finishline) set up to where I could lay down a smooth coat. I had the wall regulator set at around 40 and the regulator at the gun at 22. I diluted with 10% water and used a 1.3 tip. The main thing that was really against me today was the air temperature. It was beautiful, but then as soon as we started shooting primer, it dropped to about 55-60 degrees. So of course stuff was having a tough time drying very quickly.

My main question has to do with what finish I should expect. The final finish I got was a little “sandy” feeling. Not rough with a globs of primer or anything, but definitely not a smooth finish. That’s fine with me, but I want to make sure that’s expected and not just a problem with my setup. It seemed like the gun was atomizing the paint okay, although I definitely had trouble with it clogging up. Just curious if you have any advice or suggestions (or know of good resources to look at – I’ve watched a few videos on Youtube and they all seem to contradict each other at some point or another).

Oh, and by the way, with the charcoal grey EkoPrime, you can't see blue sharpie like you apparently can with other primers. I don't think I'm putting it on too thick, but maybe?
 
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HVLP

Never sprayed Eco but have sprayed lots of other solvent based paints. I've been told by others, the finish is sort of grainy. No idea why. Usually it's because the material is too thick to atomize in the fan or it's so fast it sets up before flowing out.
I would recommend full pressure on the biggest hose you have. It's HVLP. High Volume. Thick paint won't flow and atomize properly in a 1.3. Try a 1.8 or thin it more.
I prefer slow paint. In fact, I use the slowest activators and reducers so the paint can flow before setting up. It does mean much longer wait between coats so the chems can flash off. Usually an hour with solvent based. Just sprayed some EnduroPrime today at 60°.

If it's just internal parts, you want it as thin as possible with full coverage to save weight.
 
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Try reducing the distance between the gun and the object you are painting. It could be that the paint particles are beginning to dry before they contact the surface, in which case they can not flow together to form a continuous film.
 
Make sure you are putting the paint through a filter when you put it in a cup. I bought a box of filters from HF. That has helped a lot with clogging.
 
With the right setup it will yield a super-smooth finish. I use 85-90 PSI at the wall, Fineline 1.3, 10 PSI with the trigger pulled (regulated at the gun), air open about 1/8 turn, and fluid 1/8-1/4 turn. For this to work I always dilute it to 20% by weight (twice what they recommend) and then filter. Two slightly wet coats covers well, for corrosion protection. It tends to dry on the spray tip, so wipe it off every minute or so. To spray a wider fan for skins, same settings except the air is one full turn out. I have never been able to get as nice a finish with a wide fan, but fortunately this primer sands easily; just one or two passes with a maroon or grey Scotchbrite pad. It shoots especially well in hot conditions, but I have had good results in the 50's as well. Spray another coat or two if you anticipate sanding.
 
I would recommend full pressure on the biggest hose you have.

I used spray guns for years before I found out how much difference the size of the air hose will make. If I use a 1/4" air hose (like I usually use with air drill) the paint will always have some orange peel. If I use a 3/8" hose, it lays down smooth as silk. Not sure what size hose you are using, but it will make a difference!
 
I used spray guns for years before I found out how much difference the size of the air hose will make. If I use a 1/4" air hose (like I usually use with air drill) the paint will always have some orange peel. If I use a 3/8" hose, it lays down smooth as silk. Not sure what size hose you are using, but it will make a difference!

Using 1/2" hose with high flow fittings.
 
With the right setup it will yield a super-smooth finish. I use 85-90 PSI at the wall, Fineline 1.3, 10 PSI with the trigger pulled (regulated at the gun), air open about 1/8 turn, and fluid 1/8-1/4 turn. For this to work I always dilute it to 20% by weight (twice what they recommend) and then filter. Two slightly wet coats covers well, for corrosion protection. It tends to dry on the spray tip, so wipe it off every minute or so. To spray a wider fan for skins, same settings except the air is one full turn out. I have never been able to get as nice a finish with a wide fan, but fortunately this primer sands easily; just one or two passes with a maroon or grey Scotchbrite pad. It shoots especially well in hot conditions, but I have had good results in the 50's as well. Spray another coat or two if you anticipate sanding.

Thanks, I'll give that a try. I think I just need to play around with the combination of settings a bit more to nail down what works well. I looked at the parts after drying overnight and they definitely smoothed out a bit as they dried. Not smooth, but not super rough anymore either. It sounds like I had the air up too high and not enough primer. The description of the primer drying before hitting the surface seems like what I was experiencing. Round two of priming today if it warms up a bit, so more practice!
 
Solution

Thanks for the ideas everyone. I found a couple of issues with my gun, which when fixed, made a huge difference in how the primer went down. It's hard to say what the smoking gun was, so to speak, but two major items seemed to be primary. The first was the fact that I found that in my first session, the spray tip I used was only finger tight. After some research, I learned that the tips really needs to be snugged down relatively tight to keep air from escaping around it and messing with the airflow. I also had a problem with the regulator at the gun yesterday. I couldn't get consistent air pressure. I took the regulator apart, and sure enough, the innards were just floating around inside and not allowing any kind of adjustment. I got that fixed, mixed up additional primer and went to work. What a difference! Between a quick tack coat and then a wet coat, the primer goes on very nicely! I'm very happy with the quality.

I did do a test piece to check on durability in a week or so after it's cured a bit. I primed one side after only using Ekoetch, and another side after doing both Ekoetch and scuffing with Scotch-Brite. I'm just curious if the manual scuff is really necessary on top of the acid etch (for internal parts that never get touched after installation - for external use under paint, I think the manual scuff is the way to go).
 
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