What is Happening to My Lens?

saxyomega90125 wrote:

When used properly, in a clean room with proper ventilation and safety procedures, by someone with experience, it is certainly fine.

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High-purity acetone in a lab or professional shop is not the same as high-purity acetone on the kitchen counter or in the bathroom sink. I would not recommend using it to someone with no such experience.

"high-purity" is not well defined.  That's why chemical vendors use terms like lab grade or reagent grade, which have standard meanings.

To clean a lens, the percent purity is not so important as what the impurities are.  A chemical vendor like sigma-aldrich will guarantee that the impurities are entirely water, in which case there are no sediments to scratch your lens.  Something like a bottle of nail polish remover, no such guarantee.

Also, I was always taught in the lab that the use of acetone on coated glass should be done briefly and seldom unless it is known that the coating on that specific lens will tolerate it.

The cleaning techniques I have been taught, in three relatively reputable sources ((1), B.S. in optics, lab coursework, (2), JPL optics certification, (3), time at optics manufactures, e.g. Optimax) is that it really doesn't matter.  The overwhelming majority of coatings are safe for cleaning with acetone.  It is only some fussy protective coatings that are not safe, and first-surface aluminum mirrors which are not a concern in consumer camera lenses.

I can't speak for the lens in question, but many coatings on older microscopes and telescopes can and will be eaten over time by acetone... along with plastics, lens cement in microscopes, and your gloves.

I doubt that.  Most "older" coatings are multilayer mag fluoride, which has a soak time measured in days for 1nm of coating loss.

Every optics lab I've ever been in only uses butyl gloves, which are impervious to acetone even over a full 8 hour shift.