What is Happening to My Lens?

saxyomega90125 wrote:

AiryDiscus wrote:

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.

Well, now that I look like an idiot.... My lab experience is mainly in biology.

Thanks for the info about coatings. If it is that unusual, I'm wondering why so much of the crap in my old college lab had coatings that were susceptible to it - I have seen lab-grade acetone damage lenses there a few times. Are there any coatings used in medicine and the like that are problematic? Besides the lens cement in the microscopes. A bit off-topic but I am intrigued.

The gloves are a salient point. Chem labs have butyl around but I've seldom seen them anywhere else. In bio labs we use latex and change every hour or so when working with acetone to be safe. The usual medical-grade nitrile gloves last 10-30 minutes.

Medical devices may have restrictions around potentially/toxic materials.  A substantial number of coatings contain heavy metals that are known toxins.

Aged coatings may have also changed composition from outgassing, etc, and undergone significant enough change to alter their chemical durability.  Very cheap coatings may also be formed poorly on the surface and have relatively high susceptibility to abrasion, which is aggravated by IPA or acetone.  E.g. Canon L lenses tend to have coated surfaces with micro-roughness of 25 angstroms RMS or so, which is superior to "commercial quality."