That's a new one on me lol. And I've heard most optical myths. But seriously, the thermal shock of applying dry ice to a room temperature lens would shatter many optical glass types.
Best lens cleaner material is the dry co2.
That's a new one on me lol. And I've heard most optical myths. But seriously, the thermal shock of applying dry ice to a room temperature lens would shatter many optical glass types.
Does someone still make glass in that manner?
I'm currently restoring some civil war era windows. Everyone tells me the glass settles, getting thicker at the bottom. I've given up explaining that glass is an amorphous solid and does not settle - it was made that way, it's most likely cylinder glass. ... One of my friends has a 3000 year old Phoenecian vase in a glass case in his living room. If glass settled with time, that vase would be a puddle, not a vase.
coating or Blooming was known about from 19th century but Zeiss had the first practical process as a military patent secret just before WWII so 88mm anti air gun sights and contax II Sonnars.
I've heard something like "Glass is really a liquid, not a solid." But you can't prove it by me. I have no earthly idea why anybody thinks that, but maybe whoever told you that "settling theory" had heard the same idea someplace.
Uh....are you confusing material properties with thermodynamics? I think you might be.
If a lens can't be cleaned with Windex or alcohol it has permanent damage in my opinion.Hello APUG Forum.
I am trying to learn what chemicals will harm or strip modern lens coatings from camera lenses, or will otherwise render an optic damaged from their contact or use on the lens's coatings. I want to learn whatever chemicals should NOT be used to clean lenses at all, because they will damage, stain, strip, or otherwise harm lens coatings or lens elements to which they are applied.
Also, I would like to get a sense of acceptable chemicals to use to clean a lens, in order of their relative aggressiveness, cautions, and applications.
For example, imagine that we have a really, really tough contaminant, such as getting tar onto a lens (not that I have). What solvents could we use to remove the tar and clean the optic without running a serious risk of harming the lens or its coatings?
Would you know of some resource to learn more about this? What I see on the net is mostly the basic "here's how to clean a lens" stuff for dust and basic spots, fingerprints, kiddie smudges, etc.
Many thanks.
Henry
Just a beginner, and new to all this, but.......whenever i read "these" types of posts, I always wonder what the heck guys have on their lens.If a lens can't be cleaned with Windex or alcohol it has permanent damage in my opinion.
Here is the residue from 91% rubbing alcohol, magnified on an optical surface (ignore the round pits in the coating...a separate issue due to exposure to the environment).
That was on a surface cleaned by someone extremely anal about cleaning optics, done in a clean room to settle a bet about doing specifically what you suggest.
Those streaks from the other 9% of "stuff" in non-lab-grade isopropyl are very difficult to see, much less eliminate unless you have other ingredients in your cleaning solution.
The streaks will scatter light and reduce your contrast.
Use acetone if it's just glass and no barrel or blackening ink), lab-grade isopropyl, or windex filtered through a coffee filter. My recommendation for home use: the Arkansas sky observatory recipe and directions.
View attachment 101487
Your Arkansas Sky formula has 91% Isopropyl drug store alcohol in it, so I'm confused.
Dan I've seen the same thing (see post 27 above).
What I'm not sure is the exact failure mode. It's not a manufacturing defect like poor surface adhesion.. that would fail as a delamination or peeling off of the coating. My best guess is exposure to an environment that causes oxidation or dissolution of the coating layer and possibly the underlying substrate. The outer coating layer is often times MgF2 (magnesium flouride). So I looked up its chemical properties. Ever leave condensation on the lens? MgF2 is soluble in acid (fingerprints) and slightly soluble in water (0.0076 g/100g or 0.013 g/100g depending on reference). This isn't a lot but you're only talking a layer a few molecules thick. I've never looked into it fully but this may be a good reason to keep condensation off your coated optics! Especially in acidic atmosphere. Also why cleaning optics can be the most damaging action you can perform on an optical surface under normal use.
On lenses with this issue I've never known the full history of the lens. It appears to the eye as a haze that doesn't wipe off.
That pic was at 800x, by the way. Here is pitting at 80x
View attachment 101701
and 200x
View attachment 101702
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