Hi! This is very easy to clean soarer the headlight glass.
Yellowing is caused by Ultra Violet rays from the sun. With the UV layer intact the rays are effectively blocked from reaching the lens.
The white oxidation which forms on top of the UV layer will turn yellow and brown from a combination of ultra violet rays and
contaminants.
This does not effect the lens below. However once this UV layer is severely damaged or removed the UV rays can reach the lens
and cause it to turn yellow. When this happens there is no recovery. The yellow will permeate the lens and cause the lens it's self to
turn yellow. This yellowing is permanent, and your lens will continue to oxidize at an accelerated rate. Removing the oxidation will
not remove the yellow nor can it be sanded or polished away.
