i have a very bad build up of limescale or something similar looking on the outside of the glass.how do i remove it.ive used normal cleaning products and it will just not budge.i have no idea how it got on the outside.
Soak paper towels in vinegar and stick them over the affected area, leave for as long as possible (overnight at least) then remove and wipe clean. You may have to repeat if there's heavy deposits.