Polishing coating off a lens

[Kevin Crisp]

What would you suggest for removing badly scratched up coating off a lens? I have a big jar of stuff I used to take the scratches off a windshield and was thinking of that. Thanks.

[mhayashi]

I don’t recommend doing it by yourself.
I would suggest you ship lenses to someone professional like Jason Lane….
He has an access to recooating facilities too.

[xkaes]

Are you sure the scratching is just on the coating? If it is a real scratch, and it went all the way through the coating -- which isn't thick at all -- it's going to damage the glass. Also, is it bad enough to impact the image? Many times, it isn't, or it's in a location outside of the image area. I guess defining "badly scratched" would help.

[Mark J]

Good advice, if the scratch goes through to the glass, then polishing the coating off will just make things worse.
How old is the lens ?
Modern coatings, if done with ion-beam assist, are commonly harder than the glass underneath.
A fun story is about my friend who is a long-time telescope mirror & lens polisher - he had a 4" lens that we re-cemented and then coated with one of our normal avionic AR coats. He then decided to re-figure the rear surface as he thought there was some astigmatism. Using his normal pitch-lap and cerium oxide polishing mix, it took him a week of 2-3 hour efforts to get through the coating. He kept asking me how many layers there were, as he slowly saw each one change colour as he polished through it !