Paint Fish Eyes/ Contamination

General Composites Discussions Composites Talk
#1

I noticed now from having a small composites shop, paint contamination is a problem when working with composites supplies.

I used to wax my molds with NC770. I can tell you if you spray (aerosol) this stuff one time in the same shop you do your paintwork in… fisheye city!

Any mold release products that contain PTFE or silicone will adversely react to paint and clear coat work.

Wax your mold with silicone or PTFE products - Expect a bad, fish-eyed paint job on that part. Especially if your part surface is not perfectly smooth, has voids in the resin on the part surface. In these voids is mold release that doesn’t wash off and paint or clear coat won’t stick to.

Using a vacuum pump that releases smoke and oil into the air? Yep that will contaminate your clean part surface prior to a paint job.

What do you do then?

  1. Set up a paint booth or seperate room for paint work. Clean and prep your parts inside the booth.

  2. Wash your parts with dishsoap and water prior to painting. Rinse with water. Wipe with a clean white cloth. White cloths do not contain dye that will wipe off on the part. Let dry completely.

  3. Use a solvent based wax and grease remover made for paint prep work - follow their directions for use.

  4. Keep your painting rags out of your work shop where they can get contaminated. Use only white rags or the blue shop towell rolls for paint work. Scotch brand works very well for the blue towells.

  5. Keep your mitts off the cleaned part… your hands have natural oils on them that can cause fish eyes.

  6. Don’t store paint chemicals beside other chemcials. Someone touches the cans of paint with dirty oily hands, you go to mix your paint and then touch that same can and viola… contamination transfers onto your work.

  7. clean your spray gun with gun cleaner or equivalent solvent, store the gun in a clean place.

  8. Clean your spray room/booth regularly. Paint shops sell plastic on rolls that sticks to the walls of your booth… it gets dirty you simply tear it off and throw it away.

  9. Buy an air hose for paint work only. Don’t use it for anything else but painting.

  10. No automatic oilers on air compressor lines.

  11. Install a water and oil filter on your air compressor line. If you can’t then buy a $9 disposable ball filter for your paint gun… it will last for a couple uses.

  12. new paint guns sometimes have oil inside them… clean them prior to first use with solvent. Acetone works well or gun cleaner.

  13. Lightly tack cloth the part prior to paint and after the part has been cleaned with wax and grease remover.

  14. mold releases that contain silicone … silicone contamination won’t clean off with anything I have found. semi perms some have silicone in them or PTFE. Paint hates that stuff.

Hopefully this is helpful info.

#2

Smokey vacuum pumps: Oil lubricated pumps run in a bath of oil, and a filter removes the oil from the exhaust. However, running a pump outside of its specs (no vacuum) for more then 10 minutes, will clog the filter(s). The only solution is to replace the filter.
Also, a piece of pipe or hose from the exhaust to somewhere outside is not a bad idea.

Painting needs a clean environment. Composite shops are seldom a clean environment.

Make sure the water filter and air regulator of your paint gun is at the end of the line, not where the compressor is. Condensation can occur in a longer line.

#3

good ideas :slight_smile:

I once considered running a metal tube from the vacuum pump exhaust into a small tub of water to filter out the polutants… not sure how that would work though.

#4

That could work Fast. Bubblers are good filters. Run it through oil bath though, not water, then you can reuse that oil, if your pump is MISTING, not smoking.

#5

A pipe outside works even better…

#6

panel wipe is your friend

#7

panel wipe? you mean pre paint cleaner? We used some of that, and still had issues on some parts.

#8

Panel wipe is a solvent that removes wax, paint shops use it to remove contamanents from a panel before painting ie, dust, polish residue etc etc.

#9

I used to do a bit of respray work, what I used to do if there are contaminants that are difficult to remove completely (from say your clearcoat) with solvent you can use very fine grade wet and dry (say P1200 and above) to take it off.

#10

2 causes for fisheyes that are mostly overlooked:

-those funny bracelets, sold for charity. These give a deposit to the part where paint will not adhere. They are forbidden in the shops of many clients.

-shaving cream. No kidding. At Fokker there was an issue on below spec ILS strength, and after a couple of weeks of research, it was found that some brands of shaving cream have silicone based lubricants in them.