Originally Posted by BK
Just to clarify, vinegar dissolves calcium deposits from hard water -- in other words, it's for cleaning hard water stains, like on your windshield.
When your headlamp lenses are cloudy, it's not from hard water, it's from being pitted by dirt and road grit. They need to be polished, preferably by machine. As SpecC pointed out, you could sand first with a fine grit and then polish by hand, too. But no matter how you tackle them, it won't be with "household items." You'll need to buy a few things.
mentioned before it takes more than just one pass of fine grit sandpaper to cut this job. First you start with a more aggressive grit sandpaper to remove the aged UV coating which has failed.Then you must reduce the sand scratches and pig tails left from that paper. So you would go up in grit reducing the amount of scratches as you go. If you want clarity, you MUST
use a 5-6 step system, otherwise the single scuff and polish will still be dull.
Its no different then removing surface defects on a vehicles paintwork. First you start with something aggressive if necessary and finesse up to eliminate scratches, swirls and halograming.
Dave @ Innovative