Andre Langevin mused: > > Acetone is the best glass cleaner you can find.
Not quite - there's a couple of things I'd try if there were things acetone couldn't remove (MEK, Methyl Ethyl Ketone, would probably be the first). But acetone should get off just about any kind of oily residue, which is the most likely contaminant. I'd echo the caution to keep this stuff away from any plastic; after all, acetone has quite a long history of use as nail varnish remover. Anything that can dissolve dried nail varnish will do bad things if it ends up on your plastic lens parts. (as will MEK, come to that) The *best* glass cleaner is probably boiling aqua regis, but that's not suitable for cleaning lenses (or for use anywhere outside a fume cupboard).
