@JonD The only thing that comes to mind relates to what you said about the heat colours... As Lampies, we sometimes fine tune things to get the most out of a lantern... Do you think that your Tilley is running hotter than it should be?.. i.e. than it was designed to? Does anyone know if the 'newer' burners (X246b) burn hotter than the older ones? (Guardsmen) Is the further the colours travel down the vapouriser a fair indicator of how hot it's getting?
I thought of this thread recently when I saw a Facebook post where someone had left a perfect Bialaddin unattended for a long period. While they were away the fount pressure dropped and the reduced fuel/air speed resulted in ‘over and under burn’ and a cherry red burner dome. The Bialaddin was ‘growling’ prior to being put out. When extinguished and cold the vapouriser was bulged and stuck in the burner.... Perhaps the intent not to bulge x246b founts by keeping fount pressure low causes the vapouriser bulging problem?
I think that the question is when does carbon start to built up. Always or more at high or low temperatures. If pressure is low on a Petromax type big change is that the flame will blow back into the J-tube and will make it red hot in no time. If you get a cherry red Tilley type burner dome I can imagine that the extra heat can't escape and will deform the vaporizer. Due to the construction, vaporiser inside the burner, there is less space to expand or loose heat.