Aggressive Chemicals and Lens Coatings

[Nodda Duma]

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.

 

[E. von Hoegh]

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.

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.

 

[Nodda Duma]

Does someone still make glass in that manner?

 

[E. von Hoegh]

Does someone still make glass in that manner?

I've no idea, it's possible though - albeit not as a commercial/production operation. The panes in these windows are 30"x 15 3/8" which seems too big for bull's eye glass.
There was a local glassworks in Redford N.Y, but it closed in 1851.

 

[T42]

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.

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.

Thanks to everyone in the thread for your inputs. It has been a fascinating read and learning experience.

Henry in Atlanta (the OP)

 

[Poisson Du Jour]

Hydrogen peroxide has occasionally been used to treat / remove e.g. fungus (Zeiss does this). Coatings are pretty darned hard. That said, rubbing a snot-rag you've dropped out of your pocket onto the sand and then rubbed it on a $3,000 lens ... expect trouble!! In my long experience I think it is non-existent to get something unmoveable on a lens. In the first instance, protect the front element with a filter.

 

[benjiboy]

There isn't any need to know, just use products that are proprietary lens cleaning fluids and marketed as such , I use an American one called "Eclipse" that's brilliant, and "R.O.R" is also very good.

 

[Ian Grant]

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.

It wasn't a military secret, Zeiss were selling some coated lenses in 1937/8 before WWII, I've seen a 150mm f4.5 T coated Tessar that dates to 1937/8 and they had begun coating some of the faster 35mm lenses as well but it was a limited range of coated lenses.

TTH Cooke were coating lenses before Zeiss but not for commercial production.

Ian

 

[AgX]

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.

Our teacher chemistry told us he'd put his glasses each night on the table the other side up to avoid viscous flow of the glass...


A good example of glass being not crystal can be seen at any gadget shop where you find massive pieces of glass with some 3-D image inside.
Here the structure of the glass, by means of radiation, has been changed into a crystal state.

Same artefacts at heat formed glass plates are due to crystallisation too.

 

[Old-N-Feeble]

All matter has viscosity/fluidity until its temperature reaches 'absolute zero' but for all practical 'human purposes' glass is a solid.

 

[Nodda Duma]

Uh....are you confusing material properties with thermodynamics? I think you might be.

 

[Old-N-Feeble]

Uh....are you confusing material properties with thermodynamics? I think you might be.

Probably... I can't remember. My point is, for all practical human purposes, glass is a solid.

 

[ic-racer]

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

If a lens can't be cleaned with Windex or alcohol it has permanent damage in my opinion.

 

[CMoore]

If a lens can't be cleaned with Windex or alcohol it has permanent damage in my opinion.

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.
Shooting 35mm, all my lenses are circa 1975, just like everybody else has, and I have never seen a lens that could not be cleaned with just some distilled water. and a drop of soap. Baring some Very Rough tissues and Very Strong chemicals, how many years would it take to "ruin" a lens.?
I am not talking about looking at the lens and seeing something under magnification, but to actually see it, in a blind test, on a print.?

I do not have the knowledge or experience to say for sure, so I use that Eclipse product and the disposable, lint free, lens tissues. But like I say, what on Earth are guys trying to clean.? What are guys getting on their lens, and then not being able to clean it with some type of Water/Alcohol fluid.?
I understand the glass is coated for photographic reasons, so the coating has to be considered.
But just because you can see microscopic "contaminants" in distilled water or 90% alcohol, does that translate to any real world problems.? Does lens cleaning get more scrutinized than can be seen in the photographic prints.?
Thank You

 

[sfaber17]

Your Arkansas Sky formula has 91% Isopropyl drug store alcohol in it, so I'm confused.

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

 

[Nodda Duma]

Your Arkansas Sky formula has 91% Isopropyl drug store alcohol in it, so I'm confused.

No need for confusion. Come to the inevitable conclusion that I must substitute lab grade 99.9% isopropyl for that ingredient.

Or...try it yourself and see if it's good enough for you.

 

[darinwc]

I dont know if it is the same thing, because Ive never looked at it with a microscope, but some lenses have seemed to have hard water stains.. probably from being cleaned with tap water or cleaner that did not use distilled water.
Have you tried vinegar, then quickly following up with alcohol?

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