TheSamba.com :: View topic - Problem spraying primer surfacer today

Sun Apr 28, 2019 3:45 pm

Next painting project is our 1974 KG Coupe. As practice and because it needed to be done, I am repainting a fiberglass bumper from my 1972 911. So I hope this qualifies to post this question here.

Background: fiberglass bumper is repaired and imperfections filled. Today I sprayed a primer surfacer. The plan is to sand this down to 400 or higher prior to putting on the color. I am using an Eastwood Urethane Primer-Surfacer with a recommended ratio of 4:1.

The first problem was I could not get anything but air to come out of the gun. I turned up the air pressure a little. Did not help. Should note I was using a pancake compressor with the only pressure gauges at the compressor itself not the gun. Started at 35 psi thinking it might be around 30 at the gun. (I will be using a better compressor setup on the KG.)

Twice I poured the primer back in to the mixing cup and added more activator. I thought this would thin the primer. Just a good splash each time. Not very scientific but I was very careful with the original 4:1 mix.

Then the only way I could get the gun to spray material was to open up the fluid adjustment knob so wide that the gun actually dripped as I was painting. So while the finished product is not too bad for my first time it does have some ugly drips. Picture 3 below - those aren't runs, the gun was dripping. Being just a high-build primer I am thinking I can just sand them out.
But I need to know what I am doing wrong - I was spraying the primer while holding a paper towel under the gun to catch the drips.

Other info: spray gun is a Wood River Pro Spray Gun (with a 2.0 tip) which we bought to refinish furniture but I figured would work for paints and primers.

I know I threw a lot of variables out there but any ideas what I am doing wrong?

Thanks,
Matt

Mon Apr 29, 2019 12:08 pm

I use a $10. Harbor Freight HPLV gun to shoot all my primers. Works great. Your issue may be the small compressor. If my primer is too thick i'll add reducer not activator to thin. 2.0 tip should be good. It was only primer and is intended to sand so the runs/drips are no big deal. I get them often. :oops:

Mon Apr 29, 2019 7:36 pm

What c21darrel said, also if its a conventional gun it’ll probably need more pressure 40-55 psi from what I remember. Investing in a regulator at the gun would help also if the gun came with recommended settings along with the data sheet for ur particular primer.

Tue Apr 30, 2019 6:39 am

Yes...you need higher pressures. 35psi at the pancake isn't likely going to be 35psi at the gun especially if you have it wide open. You will have to let that small compressor catch up by stopping regularly. It will be a big balancing act trying to keep the pressures and air volumes up to where they are supposed to be and not having the product dry on you.

When I shot my dune buggies with Evercoat G2 I would thin with acetone. It made it spray much better

Tue Apr 30, 2019 1:35 pm

All this makes sense. I got the 30 psi from an Eastwood video. I did increase the pressure a little but probably not enough. I was stuck on that 30 number.

And no more activator but reducer. Also sounds like something I should have thought of. Do I need a special reducer for the prime? Can I get some now and then use it again with the paint later if I need to?

and the good news is when I go to shot the prime on the KG I will use the same gun but will have a 5HP compressor.

One last question - should I invest in a better spray gun for the paint and clear? This was not an expensive gun and as I mentioned it was bought as a wood finishing tool. c21darrel, I noticed you said you use the HF gun for primers. Do you have a higher end gun for paint?

Thanks again. This helps.
Matt

Tue Apr 30, 2019 3:44 pm

Different products react differently to different reducers. I dont spray enough to know what works and what doesnt. I always consult my friend/neighbor as he paints daily. He lets me know what I can use with the products I have and helps me pick primers and paints.
He loans me one of his decent guns to shoot paint (he has 5 or 6, different guns for different products). I prefer single stage paints, his 2 stage water based gun was like $900. When I watch him it appears to me to be super fine mist like spray. I paint anything except the car itself (bumpers, window frames, seat frames...) with a harbor freight gun.

Wed May 01, 2019 6:47 am

From the Eastwood site:

"To reduce film build, 4:1 mixture may be cut by up to 20% with a urethane-grade reducer or other appropriate solvent product. Doing this may also improve the flow and leveling of primer. Eastwood suggests using a Zero -VOC reducer to avoid potential compliance issues. Use caution in mixing materials as epoxy primer may begin to gel after approximately two hours (at 70 °F)."

Many people have commented that the Harbor Freight guns shoot well. While clearly the better the gun the better the outcome but I think technique is almost as important. A bad painter with a great gun is far worse than a good painter with an average gun if you get my drift.

Wed May 01, 2019 1:25 pm

you need to up your pressure or reduce it some. the primer surfacer I use is essentially liquid body filler, and can be sprayed on the thickness of 2 nickels

you want to spray it quick...once it kicks you'll never get that gun clean again

Wed May 01, 2019 5:03 pm

skills@eurocarsplus wrote: you need to up your pressure or reduce it some. the primer surfacer I use is essentially liquid body filler, and can be sprayed on the thickness of 2 nickels

you want to spray it quick...once it kicks you'll never get that gun clean again Please share the brand and product line you use. Also, what size tip is needed for best results with the product.

I apologize for the hijack

-----
Emil

Wed May 01, 2019 6:36 pm

I use this with either a 2.5 or 3.0 nozzle

http://www.sikkensnamobile.com/Products/Details/64?searchPhrase=&categoryId=7

I re-read what he is asking. looks like he is spraying a high build primer? not sure...never used what he is spraying, so I assumed it was a poly surfacer

the stuff I linked is not cheap, but I like it

Sat May 04, 2019 5:47 am

I'm back. I was spraying an Eastwood 2K Urethane Primer-Surfacer with a 2.0 tip. Basically a high build primer as I understand.

I clearly did a lot wrong. Tried to thin with more activator. Too low pressure. Caused drips but I should be able to take care of those. Overall though it looks good. Four light coats that I should be able to sand nicely. I have a regulator for the gun coming today and I'll shoot the paint with a larger compressor. We'll see.

Mon May 06, 2019 1:20 pm

Adding more activator would probably make it less liquid. It would harden super quick. I used to prime cars everyday. Reducer depends on what product you’re using, tip size also. I use a hf cheapo with the tip drilled for poly primer. I also have a lvlp I’ve been using. Its for a small compressor. Like $30 from home depot. Heard good things from the hf turbine setup, $99 with gun and turbine. For paint I use a Sata gun. You want it to atomize really small. You can get cheap chinease guns that perform pretty well now days. I usually use 40-50 psi but that also depends on gun. I usually use a bit more than what they recommend. High build should go on thick.

Wed May 15, 2019 9:55 am

All the 2k regular high build primers I've sprayed don't need a tip that huge. I have a cheap "primer" gun with 1.8 tip that I use for the spray on body filler type primers-they have a consistency like a milkshake. Just take a few minutes and study the data sheet for what you are using. I use my main 1.3 tip paint gun for everything but poly primer (milkshake).

https://www.eastwood.com/images/pdf/50240INST.pdf

Here it is, every professional paint product will have one of these. You can see that 2.0 is a huge tip for this stuff. Try a gun with smaller tip.

Sat May 18, 2019 2:44 pm

Another update. I sprayed the 1974 KG today with the same Eastwood 2K Urethane Primer-Surfacer. This time I used a 1.4 tip. I used a 5 HP / 60 gallon compressor instead of my little pancake and added a small regulator at the gun and set it to 32. Used the recommended 4:1 ratio with no reducer.

Had the same problem - the only way I could get the gun to spray material was to open up the fluid adjustment knob so wide that the gun actually dripped as I was painting.

Having gotten rid of one variable (pressure) my guess is to use reducer next time. That way the needle does not need to be set as far backwards. I can close up the fluid adjustment so the needle seals and does not drip and still allows the fluid to flow.

I apologize if this blindingly obvious to some but being new to painting I wanted to run this by the group.

Reducer will be my next purchase and maybe I’ll stop blaming the gun.

Thanks.

Sat May 18, 2019 4:20 pm

If you used the settings according to the data sheet for the product you’re using, then next i would suspect water (do u have anything to collect moisture?) then the gun.

Sat May 18, 2019 5:29 pm

1. Water filter at gun?
2. 32 psi seems real low....but I am just am not a pro

Sat May 18, 2019 5:31 pm

1. Water filter at gun?
2. 32 psi seems real low....but I am just am not a pro

Sun May 19, 2019 2:01 pm

Quote: If you used the settings according to the data sheet for the product you’re using, then next i would suspect water (do u have anything to collect moisture?) then the gun.

To separate water I ran about 10+ of copper to cool the air. I put a 90 turn in the line from vertical to horizontal above a down pipe with a valve to catch and then later drain water. (did that make sense? I don't have a picture). I also have a water separator connected to the regulator just before the air enters the flexible hose. I planned for this a couple years ago when I built out the garage.

Comma I did get some splattering which I've read could be water. And I got one random water drop that seemed to come from the gun while spraying. I had no idea how that could have happened. Its one thing to get some small amounts of water in the air but another to get a big drop of water. Only one though. Pretty sure it wasn't sweat although it was warm this weekend.[/quote]

Sun May 19, 2019 2:07 pm

Quote: 1. Water filter at gun?
2. 32 psi seems real low....but I am just am not a pro

No water filter at gun but tried to filter out water as described in last post. Should I consider one?

Still too low pressure you think? I didn't do enough experimenting this past weekend and I am now back to my pancake compressor for the next two weeks. I'll experiment with reducer and pressures best I can with it before getting back to the big compressor and the car.

Thanks,
Matt

Sun May 19, 2019 5:21 pm

Your water trap seems reasonable. I usually use one of those bulb filters at the gun along with the regulator.
Also, I drain my tank before any full vehicle primer/paint. I do still get water occasionally but then i just drain my homemade water trap and tank.
Do u have a gun you can borrow just to see?