Hey guys,

I bought a used set of euro headlights for my 135i because I wanted to ditch the orange reflectors. They were in decent shape, but not up to my show-car standards, so I decided to fully restore them.

I’ve done headlight corrections before, but this time I wanted to go all-in. Here’s what I did:
	•	Wet-sand 1500 (horizontal)
	•	Wet-sand 2000 (vertical)
	•	Wet-sand 3000 (Trizact disc on DA)
	•	Polish w/ yellow pad + Koch F6.01
	•	Polish w/ purple pad + Koch M3.02

At this point the lenses looked perfect — crystal clear. The last step was to protect them with 2K clear.

I used SprayMax 2K from Amazon and set up a makeshift booth in my garage. I’m on Long Island, so temps were around 50–60°F in October. I warmed the garage up a bit with a space heater, cracked the door for ventilation, and used my girlfriend’s spray-tan tent to keep dust out.

I sprayed a light tack coat, then a wet coat. Initially they looked like pure glass. About 5 minutes later I came back and saw what looked like frost on a windshield. Quick searches suggested it was due to low temps, so I aimed the space heater at them. The frost faded, but about 10 minutes later, tiny micro-cracks formed all over the surface — basically solvent pop or checking.

48 hours later I tried wet-sanding them out (2000–3000 grit), but no luck. At this point I’m going to strip them and start over, but I really want to understand why it happened.

Was my prep too smooth (since I stopped at 3000 and polish instead of leaving them scuffed)?
Or was it just the temperature/humidity being off and trapping solvent?

Any input on how to avoid this next round would be hugely appreciated. I’m going for OEM-level clarity here.

Thanks in advance!

TL;DR:

Restored euro 135i headlights to a mirror finish, then sprayed SprayMax 2K in a ~55°F garage. They looked perfect at first, then frosted and developed micro-cracks minutes later. Tried sanding them out — no luck.
Was it the too-smooth surface or the cold temps that ruined it? Looking for guidance before I redo them.


Messed up my 2K clear on euro 135i headlights — micro-cracks everywhere. What went wrong?