Need some opinions on what happened.

I sprayed two doors last Saturday - 80 degree temps / avg. humidity.

Sprayed Nason Ful Poxy and let cure for 1 hour (as the tech sheet states) before spraying the 2k primer.

Spraying the primer through a cheap HVLP HF purple gun 1.4mm tip (I know....way too small for high build primer)

First door mixed 4:1 and I could hardly get any spray through the 1.4mm tip. Had to adjust the fan to almost a spot to get any flow. It took forever to coat the door and I think I got it a bit too thick in two areas. Those two areas had very small cracks in the primer once dried...rest of the door looked fine. I sanded out only the two small areas with the cracks and sanded the rest of the door and it looks fine.

Second door added some laquer thinner to hopefully get it to spray better. The material sprayed much better but only minutes after the coating went on it cracked like a dry lake bed. Was this because I put laquer thinner and it dried too quickly, or do you think I was coating much too heavily...or a combination of both? Sanded entire door back down to the epoxy.

I am picking up another gun today probably a 1.8 or 2.0mm tip....but I want to avoid having this issue again.

 

are you sur it was laquer thinner ? not enamel reducer
or is the omni 2k an enamel primer ? enamel and laquer mixed will crack they are not compatable .

 

Yep, the lacquer thinner. PPG does sell different temp reducers for just this sort of thing. Thing is you don't want to reduce too much just to get the primer through a 1.4 tip. Use a max of a 1.8 tip and mix 4 (282): 1 (reducer): 1 (M283 or 284 hardener) or for high build cut the reducer by 1/2. Use 2-4 coats and at 80 degrees flash time would be about 5 minutes. Average flash time is 5-10 minutes at 70 degrees but just increasing 10 degrees will cut flash time almost in half as per PPG.

 

Gotcha....thanks....I was thinking it was the laquer thinner. I'll pick up some of the reducer and mix 4:1:.5 for starters and see what happens. I actually got it to spray better out of my old siphon high pressure gun, with no cracking, and I did thin very slightly with laquer thinner, but not near as much.

 

nason and omni are 2 different products,,,,,,

 

Normally I cut my omni epoxy and 2k with 10% laquer thinner and spray out of the HF gun, other wise its too thick, and have never had a problem with cracking, maybe it was laid on too thick which could crack pretty fast.

 

Epoxy and 2K high build I use a 1.8 tip, on Evercoat's Slick Sand I use a 2.5 tip. If you're thinning it so it flows through a smaller tip, don't expect the same build you'd get with the proper sized tip. Observing your flash times, build it up with additional coats.