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Priming Issues - Technique or Moisture

R

rynmss

Member
I recently ran into some issues that I'm unable to solve with my white, two-part epoxy primer.

I've utilized this product successfully on other parts, but recently I started getting spots in the first coat. I thought it was moisture, so I bled the tank, lines, etc. but to no avail. I added a desiccant filter and another moisture trap--still no improvement.

It happens on any surface, even the plastic booth wall and untreated aluminum.

Another forum mentioned that I might be applying too thick. I'd agree, that for a first coat this appears thick, though I did spray it twice once the spots appears as an initial gut reaction to "cover" them up. (I quickly realized the only way to salvage this was to abandon the pot of paint and clean off what was sprayed.)

Does anyone know what this could be? I'm not the best or most experienced with paint--in fact I likely rant toward the bottom of that list, so feel free to offer up even the most basic of suggestions.
 

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Look up “sweet cheese epoxy primer”.

My recollection is this can be a problem if you didn’t allow enough induction time for the primer. I learned to mix the primer an hour or so before spraying.

Another possibility is the first coat was too thick.
 
Interesting.

This particular primer has no induction time. But I’ll read up about sweet cheese and see what I can find…

Very much seems like I sprayed too thick—especially for coat #1.
 
Hard to say for certain without being there but it could be a handful of things:

1. Water in the air system - when did you last drain the compressor? Has it been wet lately? Or humid? Are you running the air hose with a water trap on it?

2. Oil or similar contamination in the gun.

3. Oil or silicon on the surface you're spraying. Wipe it down with solvent before spraying. Make sure your rags are clean and don't have oil or silicon impregnated in them. Use fresh rags, not recycled rags.

Hope that helps.
 
It’s always humid here, but I’ve not had these issues before. This tank sat a little longer, typically I drain the tank every day. I think this air was a week old, so to speak.

I’ve all but eliminated surface contaminants.

I’ll shoot some thinner through the gun and clean it out. New air, new trap, and lighter on the trigger. See if that works.
 
Someone else on here had some similar issues caused by contamination from the mixing utensils, in his case the syringe was lubricated with silicone.

I've had something similar occur with Nason epoxy primer when I put it on too thick, but the spots were isolated and not all over like in your picture. I now thin that particular primer with 40% reducer.

I've also experienced surface condensation when the humidity was high and the air temperature was low and close to the dewpoin, while spraying a topcoat. It caused lots of little pimples that were of a uniform size in the surface.
 
You know what. This problem didn’t start until I started using a West Systems pump lid I had in hand to get the hardener out of the jug. That could have introduced all sorts of unwanted contamination. I only hope it hasn’t fouled the whole gallon…

Well, I typically don’t like to mess with too many variables, but next run will be less paint, cleaner gun, new air trap, and no pump.
 
Contamination. Look up "fisheyes in paint "
Causes Oil ,silica ...

I used regular paper towel with once with my final chemical degreaser wipe
Fisheyes all over
 
Contamination

Looks like surface contamination, but could be airborne. It doesn't look like water to me. That usually leaves a fish eye. Same for off gassing due to too thick a first coat. It usually leaves a pin hole fish eye. That looks like something was on the surface or got into the mix. My money is surface contaminate.
I recommend buying a box of rubberless syringes from Grainger. 60ml. Label the syringes and plungers and apply packing tape so the markings don't wipe off. I use them to pull paint and measure. Plunger isn't needed for viscous fluids. I just hold my finger while pouring in the fluid. I clean them and reuse several times.
Next, drain the tank and dry the line but I don't think it's water.
It looks like something on the surface or in the mix. Wipe with a paint prep right before spraying. I use Kirker 600 but lots of others work fine. Reducer, Denatured Alcohol, Coleman fuel, Mineral Spirits, etc. The goal is a clean surface free of contaminates like oils or wax. You would be suprised what flies around the shop.
I shoot Kirker Enduro Prime 2K Epoxy primer. Mix & shoot. I have a regulator and filter at the gun. I shoot a fog coat then at least one medium coat.
I'm sure you know, but don't blow dry parts with an air compressor.
Scub with soap like Dawn. Rinse well. Wipe dry with clean blue shop paper towels and don't reuse them. Save them for car repairs. Just before spraying, wipe with a solvent on a clean paper towell. Dry with another then wipe with a tack cloth. Shoot paint and walk away.
 
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It could be fisheye. However, some epoxy primers will do this if the first coat is put on too thick. Classic fisheye has more of a crater look.
 
I’ve always used 90% iso for a final wipe before paint. PreKote provides instruction not to wipe with solvents. I’m perhaps slightly bending the rules with iso.

I just wrapped up a paint session. Applied perfectly. For kicks, I tested some coats on scrap, applying THICC. No issue. I also applied to some material that was never cleaned after the first failed attempt. No issue.

Sprayed a light initial coat on the skin and gave it thirty and followed up with a medium final coat. Looks wonderful.

I think it was contaminates introduced by the pump. I never would have figured that out without the note above about mixing sticks. Can’t be sure, but I’m pretty sure…

Thank you, everyone, for the help.
 
Alcohol

rynmss said:
I’ve always used 90% iso for a final wipe before paint. PreKote provides instruction not to wipe with solvents. I’m perhaps slightly bending the rules with iso.

I just wrapped up a paint session. Applied perfectly. For kicks, I tested some coats on scrap, applying THICC. No issue. I also applied to some material that was never cleaned after the first failed attempt. No issue.

Sprayed a light initial coat on the skin and gave it thirty and followed up with a medium final coat. Looks wonderful.

I think it was contaminates introduced by the pump. I never would have figured that out without the note above about mixing sticks. Can’t be sure, but I’m pretty sure…

Thank you, everyone, for the help.
Click to expand...

If using alcohol, don't leave the container open and make sure it evaporates. Alcohol is hygrosopic.
 
These are "fish eyes" (a nightmarish mystery) from contamination, most likely. I had an air hose that created a similar finish. Changing one parameter at a time, this problem took me almost a full summer to find (that hose went in the trash, once I confirmed it!!). Apply the first coat thin, and clean everything, drain the moisture, and try a new hose!
 
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