Microblistering problem

[ajlelectronics]

Previously I have had no problem with a Fast Mover gun. This is the second time that I have painted these panels.


Priming was done with my normal spec of Lechler Epoxy primer, allowed to harden, then flatted 800 grit dry. Panels were cleaned three times with fast panel wipe immediately before spraying.

The paint is 2 pack solid colour mixed 2:1 using Upol fast hardener with no thinners. Gun is the DeVillbiss GPI with the SATA cup system. Pressure at the gun was 2 bar with trigger open. Ambient temperature was about 11 Degrees although I did warm it up with a heater for a couple of hours first. Panels were left to air dry overnight.

The first time, I used two separate compressors, one for the air fed and one for the gun. The filtration was basic for the gun, so I put it down to that. The panels were flatted back to smooth with 1000 wet.

I purchased the

3 phase new compressor and air line so that I could feed everything through the filter pack. Everything was set up so that the gun was being fed from the whip hose. Pressure checked at 2 bar.

At the time of painting, there appeared to be no issue, the microblistering appeared after the panels dried. The problem is fairly easy to remove with 1000 grit and appears to be ON the paint, rather than in it.


My thoughts are that there is something in the paint, but that's why I am asking for your expert opinion!

 

[richie00boy]

Is the Devilbiss gun new? Could it have a tiny leak of grease from a moving part?

 

[Wendelspanswick]

Do you have filtering on the gun, I used to have problems with moisture blistering paintwork until I fitted a silica gel filter on the gun. When I have finished spraying I pop the cartridge off, put it in the airing cupboard or a low oven to dry out and then seal it in a ziplock bag till it's required again.
Never had blistering since.

The above is similar to mine but mine are 'pancake' shaped with metal threads.

 

[500e]

Almost like silicon contamination ? does not appear to be bubbles rather paint contracting from contaminated spots

 

[steveo3002]

hmm yeah doesnt really look like blisters as such , and flatting a blister would leave a pit

 

[ajlelectronics]

You can't really see in the top picture that it flats back perfectly with 1000 grit, wet. You can see from the lower picture that I have a proper filter pack, which serves the air fed mask and the gun via a whip hose.

 

[711jrp]

How many coats did you give it, was it two heavy coats by any chance?

 

[the snooper]

to me that looks like dust has fallen or been blown onto the surface

 

[ajlelectronics]

It had two coats, because I ran out of paint just before finishing the last panel. I thought it had flashed off, but as I have a couple of runs, it may not have. However, there were no thinners, so solvent pop is less likely.

 

[richie00boy]

Could it be slightly spitting because of no thinners? Usually you add 10%

 

[the snooper]

I'm still going with dust you said yourself, not evident at time of painting and appears to be on the paint not in it, what is above the spray area, I note you have a blue tarp could there be a draft blowing dust from some where

 

[ajlelectronics]

Flatting back the problem makes it vanish. However, repolishing shows where the blisters were, so I am going to flat a bit deeper and see where it stops. I suspect it is all the way through the topcoat.

 

[711jrp]

I'm thinking it's solvent pop/boil, you don't have to have thinners in for it to happen, there's plenty solvent in the paint itself, it might even be worse with no thinner as the paint could/would be loaded right up without running to get a "finish".

 

[ajlelectronics]

Paint supplier has just rung me and is extremely helpful and supportive. Very impressed!

He says water contamination. However, I just mixed a small quantity for spotting in purposes and noticed that there sems to be the same problem. I brushed out a square o an Onion board sheet and I can see what I thought were bubbles that I can push around. Supplier is going to check their binders etc just in case.

 

[ajlelectronics]

As here:

 

[the snooper]

in that case take it back anyway and get them to replace it, I never thought water as you said you have filters inline

 

[li150ss]

looks like contamination or even foreign bodies in paint. hard to really tell from pics but looked as though paint too thick, I would use a touch of thinners

 

[ajlelectronics]

I think I have had a Eureka moment! When I opened the paint, it had separated in the same way that metallic paint would, although I have never seen it happen with solid colour. It only takes a day or so to do that, confirming I think that the blue pigment is not actually dissolved in the base, or am I in pillock mode (again!) ?

 

[ajlelectronics]

This has only rested overnight.

 

[carbon]

I'd take it back to your supplier and let them see it something doesn't look good with that