Wally wrote:

Q-tips are made of cotton, a natural product, which therefore can
contain natural impurities. That can include stuff like sand (quartz),
which can leave scratches on the glass.

Maybe they could, but do they generally? People use q-tips and surgical
cotton for cleaning front surface mirrors which are much more
delicate than lenses.

Instead of using product made for babies, it's best to use products
intended for cleaning photographic lenses.

What product made specifically for lens cleaning would you suggest
for a very dirty lens? Moistened lens tissue, even if harmless in
itself, will very quickly pick up abrasive dirt from the lens. The
gadgets known as "lens pens" work wonderfully for removing fingerprints,
but I wouldn't dream of using one on a lens that wasn't already pretty
clean.

Peter.
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