Why do i keep getting pinholes in my primer?

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PostPosted: Sun May 26, 2019 3:56 pm
Hello

Im in need of help from you guys. I keep getting what looks to be airbubbels or solvent pop in my primer surfacer.

The problem is no matter what gun setting, speed or spray distance i keep getting the bubbles, even if i spray with just two turns out on fluid. Bubbles! Other than that its coming out wett and pretty flat. Its in all my coats and all over the panel.

Right now im spraying plastic bumbers. Bodywork done with p180-240. Cleand with wax and grease remover and mipa cleaner for waterbore.

The primer is mipa wbs grundfiller which is a 1k waterborne primer surfacerer mixed with the wbs water.

The gun im using is devilbis flg5.

I got one larger watertrap and two small ones.

Any ideas on what is wrong?
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PostPosted: Mon May 27, 2019 8:36 am
Looks more like trash in the picture. Do you strain the primer?



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PostPosted: Mon May 27, 2019 12:50 pm
Yes, stirred with stick, straid, stirred again when mixing then straid again into the gun. Its everywhere on the panel. Its looking good for 5 sec after spraying then it starts to pop. All the time, all the coats. Im only haveing this problem with my primer. No problem with standohyd base or profix clear. Prior to spraying i blew with air and tack.

Even if i keep fluid at minimum with one turn out and 2.5 bar at the gun i get the poping.

Im thinking it might be my thinner, cleaner or gun cleaner thats weird. But the paint looks normal when its in the cup, no strange effect or something like that.

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PostPosted: Mon May 27, 2019 2:53 pm
I am not familiar with the primer you are using. What thinner are you using with this water based product?
1968 Coronet R/T


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PostPosted: Mon May 27, 2019 4:15 pm
Thank you for taking your time and replay.

The mipa wbs grundfiller is somewhat new waterbore primer. Ive been using mipa wbc thinner. Now when you speak of it, that might be wrong. The data sheet states mipa ve-wasser as thinner but i figured they was the same since i found no one selling ve-wasser only wbc thinner. When you google ve-wasser the wbc thinner shows up.

I will try to paint tomorrow without the thinner and see what happens.

I have painted with the primer a few weeks ago without any bubbles but then i had problems with scrates showing up in the base so i had to redo them.

This primer have been giving me lots of problems.

I will try tomorrow and report back. Anyone have any experince with the mipa 2k primers?



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PostPosted: Tue May 28, 2019 10:59 am
Allright, ive done some testing.

Prior to everything i cleand my gun with just water making sure there were no left over cleaner.
Tried spraying undiluted primer on various gun settings.

Same thing. No matter setting. Which makes me think the first post here were right, that the dots are dirt of some sort. Then i tried dubble strain it with 2 190 micron filters. No diffrence.

Which i werid since i allways clean my gun in very detail.

Here is a pic from the test sheet
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PostPosted: Tue May 28, 2019 11:49 am
You are sure your painting environment is not causing this?
Dust blown up from the floor or in through a window?

If not, then it looks to me like there are undissolved solids in the primer.

Is it possible the primer is out dated or has been frozen at some point?
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PostPosted: Tue May 28, 2019 2:14 pm
I think so. I have cleaned everything were i spray and tack the same instance as i spray. I allso tried to spray outside. No diffrence.

Just gave my gun a good clean, looks like new but no diffrence.

The primer should be good till 2021. Going to try another new can of the same primer now and see if there is any diffrence but im running out of ideas. The only variables now is the gun and primer. Airsupply is the same for base and clear without problems.



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PostPosted: Tue May 28, 2019 2:47 pm
Tried another can of primer, same thing but i also tried to spray rattle can primer. Same thing. So i guess your right, its the environment. Could it be dust suspended in the air which being pushed on as i spray since it tack the same instance as i spray?

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PostPosted: Tue May 28, 2019 3:11 pm
Yes, this is why paint booths have filtered air. Also, the parts become electrically charged while being sprayed and attract dust.

You can try building a plastic sheeting enclosure to paint in and wetting down the floor prior to painting.

Another thing to consider is most of the dirt in the paint job comes from the painter. Wear a painting suit, nitrile gloves (https://www.amazon.com/SAS-Safety-66518 ... B002XXO60M), painter's sock to cover your hair, etc.

Also get a quality tack rag and gently do a quick wipe before spraying.
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