The last few weeks have been spent prepping the cabin pieces to go back into the aircraft. This includes priming, which has become a major source of complications. When priming the longerons, I noticed a slight tendency for spots to “bloom” in the primer. With everything else I was battling, I kept moving forward.

When priming the skins, the issue was greater. Noticeable spotting would again “bloom” nearly instantaneously when the primer was laid down. Within a half second, the spots would grow to roughly 1/16″ or larger.

I thought this had to be moisture, yet purging air/water from the system, adding filters, traps, and desiccants did nothing to remedy the issue. Folks online noted a few reasons this might be:

• Surface contamination: This one never had me. I prepped the surface like I always had, but more so was the fact that it would happen on the aluminum, the plastic walls of the booth, and a piece of scrap material.
• Moisture: This was my thought, but having thrown every moisture solution at it, I still wasn’t sold.
• Paint too thick: I thought maybe. Let’s be real–I barely know what I’m doing in that booth.

But then a post online really stood out. Someone had similar issues that they couldn’t track down for weeks until they noticed the mixing sticks had changed. They went back to the old sticks and BOOM, problem solved.

I hate the Eastwood primer jugs. Specifically, the activated gallon “tin.” I’ve never been able to get anything out without it going everywhere. So before priming the longerons, I shoved an unused West Systems epoxy pump in the can.

Well that pump was introducing something to the system that the epoxy didn’t like, because once it was gone so were the spots.

The sides came out good but not great. They had a consistent, but matte finish. Reasons for this were a pretty clear to me. Not enough paint, paint too thick.

I was a still worried about too thick of a coat from the online forum, but I don’t think that was an issue for me—in fact, I don’t think I was thick enough. So I kept thinning with a bit of MEK and opened up the gun a bit for the bottom skin.

And of course the piece that no one will see looks the best…

Well, we are back where we started after three weeks of chasing problems. Sometimes that is how it goes. Most of the time, it seems, that is how it goes.