Indeed, which is why I cleaned them, but what factor is the decider wether it passes or fails. I'm guessing if it blocks a certain % of the light being emitted?
this is what it said on the advisory notes.
Nearside front headlamp deteriorated but light output not reduced (1.7.4a)
Offside front headlamp deteriorated but light output not reduced (1.7.4a)
so im guesing if it was really bad it would start reducing the light output. It does look hell of a lot better after the t-cut, like new headlamps
for reference I also tried normal car polish, a strong solvent (NU-sol rapid solvent), meths, and my dad tried a buffing wheel on a dremal (not a good idea as it melted the plastic and left a nasty melt line which took me a further 30 mins with the t-cut to get out!). I also watched a video on youtube about restoring headlights and they recommended either polish or an avacado (
). As long as you use a mild cutting compound (like the t-cut) and take your time you should see results, I even read someone online you could use toothpaste, obviously being the gritty pasty type.
As for the marks inside the headlamp from what Ive re-searched you'd have to seperate the back part of the headlight from the plastic lens using heat to melt the seal (some people even suggest putting it the ovan!) then clean, re-assemble and re-seal the headlight. Personally unless the marking was really bad inside I would give it a miss as any gaps on the re-seal would lead to really bad moisture getting into the headlights and look worse than before!