hi all,
when building proj, fresnels got full of sawdust greasy finger prints etc, i see in the forms cleaning is a problem for lots of people. try this it left mine as good as new. you need a soft bristle brush, fairy washing up liquid, hair drier.
method.
rinse lenses in running warm water, put spot of liquid directly onto lens, with brush work in a circular motion from the centre out working into grooves, when satisfied both sides are clean rinse again in warm water,
with hair drier on low heat, high blow, chase of the water again in a circular motion till completely dry on both sides, dont know if the soft water were i live in scotland has anything to do with it but i had no water marks left on mine when dry, if this has any bearing highland spring bottled water should work, i believe it's exported.
good luck.