Help with spraying Target Coatings 9000 poly

[Robert Reece]

I'm relatively new to spraying finishes. I got some pigmented spray lacquer, Target EM6500. I also got some 9000 poly at the recommendation of Target. I added 2-3% of the crosslinker, also at the advice of Target. I followed the directions for mixing the crosslinker into the poly while stirring the poly with a stir stick for about a minute. Jeff at Target said that should be fine (meaning I didn't have to use a drill to mix it).

I sprayed the pigmented lacquer on some MDF and that came out beautifully. I was feeling good.

Onto the poly and things went down hill...

Picture #1 shows that the finish isn't smooth when wet - it has some small holes and lumps in it. What causes this? My spray area isn't operating room clean, but it is pretty good. I made sure everything was clean before I started spraying by wiping down with a damp paper towel. The lumps appear to be like somewhat dried finish - I'm wondering if this is where I didn't fully dissolve the crosslinker. I'm not sure what causes the little crater looking things, as far as I know there is no contaminant on the surface. Maybe I little spec of dust crept in? Thoughts on how I can get a smoother finish?
TargetCoatings-PolyProblem-2-medium.jpg

Picture #2 is a whole different beast. What happened? This was the 2nd coat of poly. I had sanded out the first coat with some 320 sand paper and ultrafine mirlon pad. I think what happened in this picture is I put too much poly on the panel and it somehow made the first layer crack. I touched it and it was definitely the first layer of poly pulling up. My gun settings weren't right and i was putting down about 4 or 5x as much poly as I should have been. I know this because I sprayed about 8oz of poly an 8 sq ft panel! Good grief. So I got that corrected, but could that be the cause of this effect? It sure makes for a cool picture though...

TargetCoatings-PolyProblem-1-medium.jpg

[Ethan Melad]

I had this exact issue with the same combination of finishes (minus the crosslinker). My initial assumption was that the 6500 wasn't dry enough. After peeling the entire 2 layers of 9000, sanding back imperfections, I recoated with 6500 and let dry longer than necessary. Then I sprayed a single coat of 9000 and let it dry longer than necessary. The second coat of 9000 was much better that the first round, but still not perfect. I can only assume there is some compatibility issue between these finishes. As much as I like Targets system, I think im going back to MLC and SW.

[Robert Reece]

Thanks for the response Ethan.

I was able to take a look at the panels this afternoon and I was also able to completely peel off the 2 layers of poly. The painted panels look like they were never sprayed!
I guess I'll let the panels sit for another day, I'll recoat with the 6500 and let them sit a few days, then coat with the poly.
I've also put in a call to tech support at Target, we'll see what they say.

[Ethan Melad]

I think another option would be to spray a barrier coat of the Target sanding sealer between the 6500 and the poly. I didn't try this, and in theory it should be totally unnecessary, but maybe it would help?