IMO Behr also goes on more evenly and just feels better to the touch.
I did some experiments to see where my issue was. I took some of the rail off cuts, along with the same 6oz glass and poly lam resin to avoid any unwanted variables.
#1- paint thinned with distilled water, dry a few days, poly lam resin with 6oz (original process)
#2- paint thinned with distilled water, dry a few days, squeegee on thin coat of lam resin and let cure, poly lam with 6oz
#3- paint thinned with behr low-lustre concrete sealer, poly lam with 6oz
#4- distilled water sprayed through airgun, poly lam with 6oz
#5- acetone sprayed through airgun, poly lam with 6oz
Conclusion: as mentioned earlier, it seems to be an issue with the paint. The compressor/airgun setup doesn't seem to be introducing any contaminants. The squeegee coat of resin pre-lam seemed to help a little, but didn't eliminate the issue. Thinning with the concrete sealer worked well. I'm sure the catalyst/temp/etc weren't exact because of the small quantities, but I tried to get as close as possible.
In the future, I would recommend against using the "folk art" brand of paint. It may just be the purple pigments, as I have used other colors in the past. But it was clearly an issue with the paint this time.
Honestly if I were to paint a board in a dark color I would use house paint. Flat interior house paint. I have done Turquoise and deep blues in the past with "flat" cheap interior house paint. Good results and no crystalization.
That which can be assorted without evidence was read in an illegal magazine.
I just want to thank the OP for posting this. I've heard the horror stories about crystallization for years, but never really seen a good example of it. This was pretty epic. And good job with the systematic experimentation. I know it wasn't the desired effect, but I think the snowflake look on the bottom is actually kinda cool looking.