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Pinholes appearing after final coat

Posted: Tuesday, March 27, 2012 4:58 PM Quote
I understand that the 2 cross-coats should be applied in thin layers (much thinner than normal solvent-based applications) ... increasing fluid amount 1/8 to 1/4 turn on 2nd, 3rd & 4th coats. However after following those directions I ended up with a zillion pinholes appearing a half hour or so after the final coat. Looked perfect prior to that. I suspect the solvent (water) was trapped and then released in the final coat.

Question is: do I need to reduce airflow or prior to the final coat let it flash off for an excessive amount of time (gave it 10-15 minutes and it was tacked up perty well before the last coat)? Thought leaving it much longer would result in orange peel and it will not flow together well.

This is proving to be quite different than normal painting and I just want to dial in on the solution please.  I'm using a decent paint booth, good clean dry air (3-stage dessicant air dryer), and a SATA 4000b at 25 psi.

Suggestions? How have others overcome this issue?
Blue skies & tailwinds,

Kevin
Posted: Wednesday, March 28, 2012 11:31 AM Quote
... after reviewing my process I think the issue may be that I put on the final coat too wet/heavy. It's hard to unlearn old habits. I'll back up a step and shoot a few test panels (as Jason suggested previously). Will post results after I get that done.

Questions relating to the repair of small pinholes: After sanding the expensive yellow primer(#400 wet) can I just put on a couple coats for coverage or must the whole process be repeated for repair of pinholes (4-5 coats)? This will only work of coarse if there is no breakthrough beyond the white base. I am using Sport Yellow which is very transparent and wonder if the color will look a lot different with the additional coats (added just 2 coats to the rudder and didn't see a lot of difference)?
Blue skies & tailwinds,

Kevin
Posted: Wednesday, March 28, 2012 7:13 PM Quote
Yes if you have pin holes or small craters in the paint especially if you rushed the last coat or put it on very wet what you're getting what is called solvent popping. In cold or damp environments you should extend your time between coats. Research solvent popping on the internet for more detailed information.

first coat should be about 50% color saturation and pretty dry/satin looking
second one look for 90% color saturation and again not wet but a semi dry/satin looking finish
third should be total 100% color saturation but not a full wet coat yet. Also do not apply a orange peel looking coat either
The last coat should be applied when the tack coats are properly set. Don't rush it the tack coats will reach the proper tack with little to no color transfer and hold that tack for a few minutes. Just make sure the tack coats have not dried or you run the risk of getting a paint run or sag. The last coat needs to be shot so that it goes full wet about about 3-4 seconds after the paint gun. Just make sure you get a wet look to avoid having an orange peel surface.


Jason
Posted: Tuesday, June 05, 2012 2:36 PM Quote
To follow-up, we determined the yellow EkoPoly was made with a bad batch of resin. Stewart Systems replaced the paint and the new stuff was MUCH easier to apply. I did end up spraying at higher pressures (25 to 33 psi) to get it to work well at 20 to 21 seconds viscosity.
Blue skies & tailwinds,

Kevin
Posted: Monday, October 22, 2012 2:07 PM Quote
Had a chance to spray with the new Eko Poly Premium and it is much, much better ... no pinholes. Easy to spray and behaves well, similar to an acrylic urethane. Does stay wet for quite some time so if you're in a dirty environment you may get to test it's buffing properties. I sure like it though and think Stewart Systems is on the right track with that formulation!
Blue skies & tailwinds,

Kevin