Priming. Kicking my butt. What am I doing wrong.
OK here's the deal. I'm trying to prime the roof of my 89 crewcab pickup. I keep getting horrible dry spray beside where I'm priming on the roof. Now the cab corners and front pillars turned out fine.
1. Gun is a warwick HVLP 12 year old $170 paint gun with a 1.4 tip. Guns rated for 60PSI. I was shooting around 60PSI at the gun I had fluid knob setup to right off the trigger back stop. On the flow control the only way I could get a wet coat was to adjust the fan control until I got about a 6" wide pattern when about 6" from the surface. I've used this gun for years as my only gun and have done relatively well in the past.
2. Primer was a AutoBody Masters Urethane primer Surfacer. Primer Link I mixed it as they said for Medium build primer. I was using the fast catalyst. Now it states to use a 1.5-1.8 tip. I was using my gun with the 1.4. From previous experience I would have thought this just means I need to slow down to get a wet coat since I'm not flowing as much with the smaller tip.
3. I wasn't priming with an exhaust fan on.
I had a heck of a time getting a wet coat on the roof. once I got it setup OK it did go fairly well I had to go slow though to get a wet coat. My problem is I kept getting a lot of dry spray on the opposite side of the roof. I'm guessing I wasn't holding my gun parallel to the surface and was shooting product onto the far side. The far side was also the first side I sprayed. That product was then clumping up and sitting on the opposite side? I can brush it off by hand, but the surface of the primer underneath is still fairly rough feeling. I can sand it off, but wondering what is happening here.
So Recap. 1st side of roof sprayed OK. I went slow and put down a decent wet coat. Looked good when done. Sprayed second 1/2 of roof. Looked oK. when I get down I notice tons of dried primer "dust" or "globbules" on the first side. These globbules can be brushed off, but the surface underneath is still rougher now then when sprayed. I can check on getting pictures still as I haven't messed with it since I sprayed it last night.
Sorry for the book, but looking for some help. Also anyone recommend a decent primer gun for around $100?
It sounds like the tip is too small for the viscosity of the material you're spraying. You can either use a larger tip or try adding a little reducer to the mix.
Also, make sure that the breather hole in the lid of your cup is open, if clogged it can cause this problem.
Len - Thanks for the ideas I really appreciate it. Also do you setup a primer gun different than a paint gun? Or does your video apply for both?
I did try a cheap gun with a 1.7 earlier and had similar problems. I'm wondering though if I just had the settings jacked up. I agree I need a bigger tip and think i need a better primer gun for more consistency.
I did have it mixed the 4:1:1/2 that it allows so I had a 1/2 part of reducer in there. Next time I'll up my reducer a little more. I'm thinking it was too thick.
I do know that the hole in the lid was clean open.
Any other thoughts?
A HVLP that specs 60 PSI?
HVLP is high volume, low pressure, that's not low pressure.
I hear ya on the 60 PSI. I know I checked it and it has HVLP and 60 PSI on it.
these are a couple pictures showing what I was seeing. I hope they show the dryness.
I'm thinking about a Sharpe 3000 with a 1.8 tip for a primer gun. From reading sounds like a lot of people like them and use them for primer and it's in my price range.
Try to drop the pressure 10-20 psi.
I would get an FLG3 gun from len with the 1.8 and 2.2 setup. Spent the extra money and the Finishline will last longer than the sharpe. I don't like the rubber air gasket in the air cap of my sharpe.
Be sure to put a nice even guide coat over the surface before you start wet sanding with 400 or 600 grit sandpaper. The guide coat will help you see that you've sanded the surface until the dryness has been eliminated or it will help show you if you need more primer.
Nice reminder on the guide coat. I spaced it off on my first wet sand. You would keep doing the prime and wetsand cylcle until a person is happy with the finish correct?
Also thanks for the recommendation of the FLG3 gun. I appreciate it. I'll have to review it again. i keep eyeballing the plus for a new topcoat gun. Not sure if i could justify a tekna, but the way they get raved about I might try to spring for it.
And Regarding dropping the pressure. Higher pressure equals better atomization correct? Low pressure equals coarser fluid droplets? So when I was spraying higher pressure I was getting small droplets which for primer really wasn't needed. Do I have this right?
Now when I spray base and clear I would want to up my pressure again to get the atomization? I'll shoot a test panel for sure.
Thanks again for all the help and comments I really appreciate it.
Sounds like whats happening is with all the pressure and the small nozzel, you are drying the primer before it gets to the panel. Id drop the pressure to 30-35, maybe add a little more reducer.
For the base and clear, you may want more pressure, but there is a sweet spot. Too much pressure and you are drying and blowing it off the panel, not enough and you dont get good atomization. I have never heard of an HVLP gun needing anywhere near 60 psi. 30 psi is usually more like it. But I havent seen every gun...so I dont know for sure.
junk you can drop the pressure for the base before you drop it on clear. The lower I drop for my primer the less over spray I get and the more build for urethane primer.....especially when spot priming.
I picked up a standard catalyst versus the fast catalyst i had bought before. I was going for a quicker dry time, but since I'm having dry spray problems figured I didnt' need anything helping dry it faster. Is that a good move?
urethane or epoxy primer as a sealer? Both of the primers I've been using can be reduced down to be used as a sealer. As I don't plan to sand the sealer coat I would consider the epoxy for better adhesion, but if I screw it up and need to sand the urethane will be easier to sand.
Either way on the sealers I figure if I reduce it down as they say or possibly a little more and then drop my pressures I'll get a good coat. Any tips on applying the sealer nice and smooth before top coating since I don't plan to sand it once applied.
Also here's a picture of my gun. Just overlook all the junk on it. If this is their low pressure I would like to see a high pressure gun. I bought this mainly because I wanted a gravity feed and at the time the paint store had this line or like $500 sata's. So I went this route. It's worked fine, but I'm read to replace it. Although I'll probably use it to finish this project.
I hate to be the one to break he news to you but with a cheap gun you're probably going to get a "less than satisfactory" finish. The sealer needs to be applied as smooth as the paint but I doubt that gun will apply your finish very smoothly.
Originally Posted by junk
Do I think a better gun would yield a better finish, sure I do. I don't have the coin to pickup a new gun right now. So I'll make the best of it and go from there. I've never dug into my setup or technique this much before. Typically I've just sprayed. Now I'm trying to gain the underlying knowledge so I can make better choices going forward. What variables are involved and when to do certain things. And even what products and tools to buy and what the differences/advantages are.
Thanks again for all the help and insight! I have some good info to use as I continue this project.
Last edited by junk; 03-21-2012 at 12:17 PM.
Ok I keep reading about adding more reducer. I've typically always followed the data sheets directly. So the primer i'm shooting does 4:1 full body, 4:1:1/2 medium body, and 4:1:2 sealer. So can I go beyond the 4:1:2? is there an accepted standard for reducing products beyond what the data sheets say?