Well, I was kind of wrong about the green thing.. but the fact the white is probably an epoxy ink applied prior to reflow is correct.
Maybe just something that happens when old..What Is Silkscreen On a PCB?
www.pcbgogo.com
They weren't really designed to be "reused".
For the few I did I never had much problem with the white and reflowing (using a hot air fryer btw) BUT using leaded solder on clean boards allowed me to use much less heat.
The lead free solder used on most boards nowadays can be the issue when repairing stuff like this.
alos the fact that al core circuit boards really dissipate heat.. as they should.
Bought one of these but never used it. well not that exact one.
I'd have to look but think I never went over like 390F for the leaded solder.
For 14$ I'll let you know how it works I'll market it lol.