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"Fish Eyes paint defect"

An ongoing discussion beginning back in 2005 ...


Q. I Manufacture/Finish parts and frequently encounter Fish Eyes on products. I have tried many ideas to narrow down the contaminant but always fail. After some time chasing the problem mysteriously disappears. I am in a Class 100 Clean Room and go to great lengths to make sure my parts are cleaned before they enter into the Clean Room. I have tried cleaning with Naptha, Acetone [affil. link to info/product on Amazon], MEK / methyl ethyl ketone, etc but with no resolve. My process is consistent with each part produced. Nothing has changed, no additional processes or chemicals but the fisheyes come and go. The problem is not part specific but is sometimes paint specific. Even my paint supplier spends endless hours trying to assist me with the problem. No one can figure it out. I have come to the theory that it must be an air borne contaminant from a nearby factory (since we are surrounded with factories).
I would appreciate any assistance.

Dan Casey
Manufacturer - Fujian, China


A. Fish eyes are an air-line or airborne contaminate. Don't bother looking any where else because it's a waste of time. They are caused by an atomized, petroleum or silicon based product. All you can do when they appear is look for something that is happening that isn't happening when they aren't present, like maintenance doing PM's, or air dryer malfunction. I recently solved a fish-eye problem simply by realizing that they only appeared on the product during the period of time that the air-conditioner cycled on. They only appeared in one of our paints, so when we run that specific product the painters turn off the A/C and the fish-eyes are no longer a problem. I still don't know what caused them and probably never will.
Another time I had fish-eyes appear suddenly and it took me 2 weeks to finally track down that the day they started was the day that maintenance sprayed WD-40 [affil. link to info/product on Amazon] into the coolers to lube them. Of course the coolers blew the WD all over the plant.
Then there was this other time(are you getting bored yet?)when the filters that were between the air-dryer and the paint booth never got checked, and they got full of oil, the oil would get pulled into the paint gun feed line and atomize with the paint and produce fish-eyes.
Another time we had intermittent fish-eye problems, we found that the brake operators were hiding cans of oil that they used for spraying oil on their tooling(and contaminating the air), they hid them because they didn't want anyone taking them away(who cares if they produced thousands of dollars worth of paint rejects, right?)
This particular problem just takes a lot of detective work. Good luck.

Sheldon Taylor
Sheldon Taylor

supply chain electronics
Wake Forest, North Carolina



A. Sheldon has his experience. I had one experience with a hands care cream called "Atrix". One of the ladies in the line uses that cream and contaminate the pieces. It takes few weeks to find the origin of the contamination!

Jordi Pujol
- Barcelona, Spain

June 2, 2011

Q. I do have fish eye problem now. It is in the UV clear coating for plastic camcorder casing. All action to track down the root causes has been done. But the defect keeps on occuring. Please anyone can help?

Hafiz Abd Rahman
- Shah Alam, Selangor, Malaysia

August 25, 2019

A. Fish eye can be caused by your air compressor (blow by) adding a fine mist to the air supply; you will need a very good water trap in the system, and don't forget to wash out the inside of the air lines.

Stuart Stancombe
ssmotorsports - Victoria Australia

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