Reducer or Retarder???

N

Nomura

Hello Members... I'm a beginner...this was my first overall spraying 4100 UV clear and 4104 Very Slow Activator over PPG Waterborne Envirobase. Using an Anest Iwata Entech LS400 1.4 Tip (green cap). I was trying to find it's "sweet spot" so my regulated air pressure varied 22psi to 28psi. Results were somewhat satisfying, considering it was my first, although it was way short of spectacular.

I ended up using 26-28psi for the most part, but it seemed to spray a little dry... temperature that day was a hot and dry 97F degrees. Is it wise to choose a higher pressure when temperature is high?

I now realize I should have added some "Reducer"? or should I have added some "Retarder"? or both? How do they differ?

Also, 10 days later while cutting the clear I noticed these small areas of micro-bubbles, only on the hood. Would this be a result of not using a Reducer or Retarder?? My thought is... because the hood is on a horizontal plane, tipping the gun excessively and sucking some air down the cup would cause these micro bubbles to develop. I dunno, please advise.


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They are either co2 gassing or solvent pop. if they showed later it co2.
retarder is best from stand point you use a lot less to do the same thing as with slow reducer.
Air at gun 28 is good but more important air at wall needs to be min 125. is wall pressure is 70-90 this could be all your cause of problem.
 
It's hard to tell from the pictures, but if the material was going on dry, that look could simply be texture from small/tight orange peel that wasn't sanded out completely. The reason I wonder if it might be that is because solvent pop usually only happens with heavier or wetter applications. If it is texture, I would maybe worry about remaining film thickness in that area. It could be that several more coats of clear in those areas are called for, but it's hard to tell.
 
Thanks Barry, Im anxious to try using the retarder next time. No...I've got plenty of good, clean air. I sprayed 2 coats uv clear, then cut it with 600/800... had lots of orange peel, trash... and I leaned on it twice, while reaching for to roof.:rolleyes:...but no runs, and definitely no bubbles.
Ten days later, I sprayed 2 more, with conscious intentions to address my previous errors. I changed attitude, technique, increase gun pressure... and this is what I got.

I agree with crashtech, I'm assured this isn't solvent pop... they're just too small and too many... not easily visible to the naked eye.
Granted the UV clear and 4104 has been sitting around for over 2 years... but I've experienced this before on another project that was sprayed by a pro when the UV clear was fresh.

crashtech... that is correct, I decided not to sand it out. In the small the area of a "penny", there are hundreds of tiny bubbles suspended deep in the clear. The more I sand... more bubbles appears... so I just left it alone. If you notice the clear coat is actually flat... it's just these tiny exposed bubbles become open craters when sanded.

Oddly... even though I had dry spray, I ended up with heavy runs in several areas.:confused:

Admittedly this isn't my area of expertise and I'm not familiar with CO2 gassing... but logically speaking, this kind of bubbling does occur in liquids through "cavitation". "CO2 gassing" may just be a result of "cavitation" ...which is a rapid formation of vapor bubbles within a liquid...when the liquid goes thru a rapid pressure drop, like the venturi of a spray gun.

There are other experienced members here that shared similar results with no solution. I'm just thinking out loud, but the probability of cavitation should be considered when other possibilities have been ruled out.
 
@Nomura , now that it is obvious that these were small bubbles, I have to take back what i said. It IS solvent pop, and it may have been fixed by the addition of some retarder. 97° as a surface temp is almost too hot to spray, imo. The material had to be skinning off before the solvents got out. In such conditions, I would probably get up at the crack of dawn to do my spraying at the lowest possible temps.
 
thank you crashtech, definitely going to try the retarder next time... the temperature that day was 97, the surface temp could of easily been higher in the booth, I dunno... but I'll be more conscious of this next time.

I'm not doubting you, I'm just not completely clear on what "solvent popping" is. Are you saying the solvents within the UV clear did not have a chance to fully flash off because of high temperatures? "skinning off"? does that mean drying off? I'm thinking spraying too far away can also have attributed to this?

I've seen this once before when UV clear was sprayed by a professional at a different location, different car and when conditions were much cooler. It was just a small patch on the horizontal section of a hatchback, opposed to mine being limited to 3 small areas on the hood... but he didn't know what it was.
 
@Nomura , Many kinds of defects are caused by the very top layer of the finish drying before solvents can get out from below. Mild versions of this looks like dieback, loss of gloss, shrinking, edge mapping, etc. Solvent pop is one of the more severe forms of solvent trapping, the trapped solvents actually come together in bubbles somehow. In milder cases, you might see it along an edge where clear flows and piles up a bit, but when it's bad, it will be all over starting with horizontal surfaces.
 
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