Cleaning optics: what your mother (probably) didn't tell you about the soap

In everyday life and in the lab, there is often a mundane but important problem: cleaning optics.
It can be your glasses, microscope objectives, AR-coated lenses, or microscopy coverlips.
There are many comprehensive online resources on the topic, such as Newport tutorial and Photonics review.

image credit: https://photographylife.com/the-effect-of-dust-on-lens-bokeh

In practice, I found that achieving clean surface of glasses, lenses, and coverslips is really hard when using recommended organic solvents. I tried chemically pure 99.98% ethanol, isopropanol, acetone, with and without sonication, gentle wiping with special lens tissue pads from Thorlabs and generic lens tissue. Almost always there is some residual dirt, smudges or dust.

Out of desperation, I tried ordinary soap from lab dispenser - applied, gently wiped, rinsed with distilled water, dried with optical tissue. THIS THING DOES MAGIC. The cheapest and most effective way of cleaning optics ever. This became my only way of cleaning glasses, lenses with AR coatings, and coverslips. Haven't tried with filters - will test them soon.

So, simple protocol:
- blow off dust
- apply liquid soap or soap solution
- gently wipe with finger or optical tissue
- rinse with a lot of tap water, if possible (unmounted lens)
- using distilled or better deionized water, rinse (unmounted lens), or wipe clean with wet optical tissue,
- dry with compressed air or optical tissue.

Better use liquid soap (green stuff from lab dispenser), without any abrasives or perfumes.

Disclaimer: I suppose there are optical elements which should not be cleaned with soap - perhaps those with protected aluminium coatings or some other special cases, check the table and proceed at your own risk if unsure.

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