Most of the responses are greatly appreciated, especially since I will go with a Precat on the next job.
To Chemmy, I will add that my first attempt, I shot all of the doors' topcoat, 31F to 60F outside, but after shooting each door, I put the door immediately in a temperature controlled box and immediately turned on my torpedo heater to the right of my spray table ( above the table was a 2x5x1 insulated box with a heater. Down wind of my heater, to my left, I built a series of drying racks that hang from the rafters to where the heat from the torpedo will go. The torpedo heater helps clear the air of solvent fumes (in exchange for a touch of carbon monoxide), to help the point of capture air evacuation system that comes down from the rafters and constantly sucks. ... The microbubbling happen in the cold, in the warm, any gun, with 25 percent lacquer retarder. The primer and problematic finish was Lenmar. I need to pull the sds on this product and call the technical support to see how they have improved this formula over previous generations of nitro cellulose.
For anyone interested, yesterday, after a week of wrestling, reading, and trying everything - - I finally solved the microbubbling issue after a week by adding 10% to 20% acetone to the spray cup!!! My theory was that it was most likely h2o coalescing from the air, the pigment, or the lacquer paint. Water is heavier than the lacquer or any of the solvents so was not magical rising out of the horizontal paint film. ( I spray and dry the doors horizontally, as I found I could get the best build, best leveling, and the zero possibility of any run developing, except for the occasional run on the less visible lip/door edge.)
I have not ruled out the possibility that the microbubbling wasn't caused by the lacquer formula, because I did try using a chip brush application on a 7 inch round plastic lid, and the microbubbling still appeared, which indicates environmental, brand of lacquer, or pigment cause. (I have used this base for years, sprayed cabinet doors in the same environment for years, tried 3 guns, tried xylene (high and low percentage) and 25 percent Lacquer retarder, I varied the temperature up and down, and humidity up and down, I did try tinting a quart of the same brand with ppg pigment rather than Benjamin Moore, I tried letting my paint cool overnight, I tried using paint warmed to 80F, I tried thick coats, thin coats, I tried straight unthinned lacquer paint, I tried lowering and raising air pressure, I switched brands of water separator at the gun to a desiccant and left the oil water separator at the compressor as the metal clear type. I did not notice the clear separation filter getting foggy like times in the past where microbubbling was never an issue-this made me wonder if it was doing its job.)
I ran into an old forum post from a guy who successfully topcoated his nitro cellulose lacquer with a Precat Lacquer by mist coating, 320 scuff sanding, another mist coat, another 320 scuff, then full topcoat of Precat. I am tempted to clear coat the set of doors with a Precat to better protect the finish, on the front of the doors. (I am being told that the Precat does not expand and contract like the nitro cellulose, and might crack. However, I was told, in 1991,the same thing about porch floor paint, and I was not supposed to prime, because primers were flexible. I learned by 2001, that porch floor paint lasted longer if I used a high build flexible paint under to act as a buffer, because wood expands and contracts a crazy amount. If you think about it wood swells and skrinks something like 10 percent, depending on the humidity, and the miniscule flex of a base coat is nothing in comparison. In fact, it might help buffer a less flexible topcoat from a wildly expansive, flexing base wood substrate. We see hard inflexible top coats cracking after 6 decades, but they also crack and checker when they the base coat. I am not convinced of cracking risk, especially when the people who warn against have never tried it, nor do they apply the coatings for a living and having at least a few decades to witness the various phenomena in the field. I will only trust a first hand witness, not urban myths, as proven by the Discovery Channel Series called Mythbusters.)
For others Googling this problem years from now, I also tried spraying all the doors with 3:1 lacquer thinner to retarder, and straight retarder to melt out the bubbles, but they did not budge. Even sanding, then hitting with the retarder. I also tried clear coating with a lacquer to see if the bubbles became less noticeable, to no improvement in appearance. If these were mere air bubbles melting with a retarder would have fixed the problem. It had to have been hard core water or mineral spirits bubbles - some incompatible liquid, which the acetone was able to bind to and carry up the surface, as acetone is going to be the first, lightest thing to flash off. Acetone is used to dry out beakers in a chemistry lab, and has at least some water solubility I was told by a chemist or two. Most likely the paint somehow had some water getting into it, or was pulling water into it from the air, and the acetone carried it out. Else, the last day and a half was a fluke. Yesterday, I shot all the doors, outside air was 28F, no bubbles with the acetone. I skipped the climate controlled warm box, as I wanted slow drying, incase that might help with the bubbles. So they just had the benefit of me cycling on the torpedo for 2 minutes after each door. But really, the acetone, seemed to be the ticket. I would open and stir up paint on the assumption that the acetone would rise and separate in the cup after every 1 or 2 door sides, and I periodically added more acetone on the theory it would be quickly evaporating through the tiny hole in the top of spray gun and out of the tiny hole on side of the plug, plus every time I stirred. I was too much of a coward to shake my cup for a likely unfounded fear of making the very bubbles that I was trying to prevent.
So, rather than switching brands, in solvent materials, perhaps, adding acetone might be something that can be reproduced by others with this problem. Unfortunately, it will be someone 7 to 10 years from now, and the thread will be closed, and I & others will be deprived of their valuable and sought after input.
So, theories about too thick of film, and other straw grasping seems to be incorrect. The occurrence in Emerald Urethane water borne spraying is like due to a different cause-the surface tension lowering agents needed to avoid goose bumps, beads, caused by the higher surface tension of water.. This solution would not apply to water based materials.
As a reminder, I am still waiting for replies on the possibility of clear coating with a Precat clear, especially using the double premise method. As well as figuring out if it is even necessary.
I have been doing cabinet doors for a condo and apartment complex for years with this Lenmar product (working through the management), and have no complaints yet. On residential repaints, we mostly used water borne urethane and alkyds, which seems to inferior to the Lenmar lacquer. I watched a builder from 2003 to Dec 2008 use this same Lenmar on all the trim, and thought it was superior to any oil that I could apply, at least for the first 6 months to a year as my finish cured. I got into catalyzed 2k urethanes in 1996 and quickly got away from them as they were nearly impossible to keep from running and dirt to get into the film=unsuitable for the typical nitpicking client...
I have some black doors to shoot and will need to test my hotbox and acetone. If this combination escapes the microbubbling issue, it will allow faster drying and limit the stray dust that plagues the slow drying... Typically, in the winter, I would shoot 30 doors, 20 would dry perfectly but 10 would have some flaw from a dust spec, or my error when moving to the drying location, etc. So I would need to fix 10 doors, and reshoot. Then, nearly always 3 doors would have some imperfection and I would need to redo, leaving me with 1 door that didn't turn out. 2/3rds of the time I can just redo that door and have it perfect. So 30 doors is really 30+10+3+1=44 doors. I was really hoping a dust proof warm box that I could set them in for 15 minutes while I prep the next door would eliminate the random dust problem. If successful I planned to build it capable of drying 4 doors at a time. Hopefully, this would mean 40 minutes before allowing a door to exposed to the non hermetically sealed environment.