What is Happening to My Lens?

I very much doubt that you have damaged the coating, it is much tougher than people believe, often it is harder than the glass underneath it.

I have never used Pancro lens cleaner but I expect it is just a soap solution in purified water like most cheap lens cleaners.

I think you have just dispersed the sunscreen and spread it over the surface, if it is an oil based sunscreen then you need  isopropol to clean it off which will actually dissolve the oil. Apply the isopropol to a soft tissue, wipe the lens and discard the tissue, repeat as necessary with a fresh tissue each time until all trace of the oil has gone. finally clean the lens with a tissue and lens cleaner. Do not at any time drip any fluid directly onto the lens surface.

Any marks like this will not really affect the sharpness of the lens but will make it more like to show flare and loss of contrast.

zackdezon wrote:

After using Pancro and a microfiber cleaning cloth on this lens that got a little sunscreen on it, this streaky, hazy area has appeared and it doesn't want to go away. My fear is that I've somehow stripped the coating. Anyone familiar with this? I've taken a few test shots with it and everything seems sharp so far. Haven't noticed any haze over the images, either.

Your coatings are damaged.  The front group will have to be replaced to remedy the problem, which is ~$350 from Canon.

You shouldn't use Pancro or other lens cleaning solutions on the 24-70 II, it has coatings with unusually poor durability.  The dilute acetone or isopropyl alcohol in that cleaning solution will degrade the coatings over time, culminating in the damage you see here.

Ray UK wrote:

I very much doubt that you have damaged the coating, it is much tougher than people believe, often it is harder than the glass underneath it.

No, coatings are never tougher than optical glass. Amorphis solids are bound to be much more robust than atomically thin layers of combinations of precious metals (solid at room temp) and other elements (e.g. fluorine, gas at room temp). Both the thinness and significant composition by mass of gasses makes coatings relatively fragile. they only have perceived durability because they sit atop a quite strong substrate.

I have never used Pancro lens cleaner but I expect it is just a soap solution in purified water like most cheap lens cleaners.

Not so, isopropyl alcohol or acetone. Soap would leave a residue.

I think you have just dispersed the sunscreen and spread it over the surface, if it is an oil based sunscreen then you need isopropol to clean it off which will actually dissolve the oil. Apply the isopropol to a soft tissue, wipe the lens and discard the tissue, repeat as necessary with a fresh tissue each time until all trace of the oil has gone. finally clean the lens with a tissue and lens cleaner. Do not at any time drip any fluid directly onto the lens surface.

You can drip IPA on optics all you want. Most of them are ultrasonic cleaned by submersion in an agitated solution of it anyway.

You shouldn't* use cheap IPA or acetone (e.g. nail polish remover, paint thinner) as they are low purity, e.g. 96% in some cases. If the impurities are particulate matter, the forced streaking of them across the surface is all but guaranteed to damage the coatings. Using lab or reagent grade (99.8, 99.9% purity) hedges your bets on that.

Some may find this advise to be overly cautious, but a small quantity of "proper" chemicals is a much cheaper investment than a ruined front group. 1L of 99.5% acetone with the remaining impurities guaranteed to be water is $44 from Sigma-Aldrich, which is ~2x cost over something like a bottle of nail polish remover.

e: you should also use lab tissues, e.g. kimtech wipes.  Facial tissues, e.g. kleanex, puffs, contain oils and other compounds designed to sooth the skin that you do not want to streak on your lenses.  Lab tissues are only a suitable type of paper, and designed to lint less.  Lab tissues are cheaply available, even sold by Amazon.

Ray UK wrote:

I very much doubt that you have damaged the coating, it is much tougher than people believe, often it is harder than the glass underneath it.

I have never used Pancro lens cleaner but I expect it is just a soap solution in purified water like most cheap lens cleaners.

I think you have just dispersed the sunscreen and spread it over the surface, if it is an oil based sunscreen then you need isopropol to clean it off which will actually dissolve the oil. Apply the isopropol to a soft tissue, wipe the lens and discard the tissue, repeat as necessary with a fresh tissue each time until all trace of the oil has gone. finally clean the lens with a tissue and lens cleaner. Do not at any time drip any fluid directly onto the lens surface.

Any marks like this will not really affect the sharpness of the lens but will make it more like to show flare and loss of contrast.

i strongly disagree! i never use any kind of liquid (lens cleaner) on my lenses for any reason, except for a damp MF cloth--even for suntan lotion. using alcohol on a lens? no way...that is bad advise!

1Dx4me wrote:

Ray UK wrote:

I very much doubt that you have damaged the coating, it is much tougher than people believe, often it is harder than the glass underneath it.

I have never used Pancro lens cleaner but I expect it is just a soap solution in purified water like most cheap lens cleaners.

I think you have just dispersed the sunscreen and spread it over the surface, if it is an oil based sunscreen then you need isopropol to clean it off which will actually dissolve the oil. Apply the isopropol to a soft tissue, wipe the lens and discard the tissue, repeat as necessary with a fresh tissue each time until all trace of the oil has gone. finally clean the lens with a tissue and lens cleaner. Do not at any time drip any fluid directly onto the lens surface.

Any marks like this will not really affect the sharpness of the lens but will make it more like to show flare and loss of contrast.

i strongly disagree! i never use any kind of liquid (lens cleaner) on my lenses for any reason, except for a damp MF cloth--even for suntan lotion. using alcohol on a lens? no way...that is bad advise!

Isopropyl alcohol and acetone (a much stronger solvent) are used every day to clean an enormous number of lenses.  It is fine, but each coating must be evaluated for its durability when exposed to these chemicals.  A select few coatings are not resilient enough to this sort of chemical attack.

Andy01 wrote:

Alcohol maybe, but acetone NEVER !

Acetone is a VERY strong solvent - it is nail varnish remover. Designed to dissolve things. Used to soften resin etc.

Sorry, but only a complete fool would even consider acetone to clean a lens, unless they wanted to create a paperweight.

Colin

So is the largest manufacture of stock optics in the world a complete fool?

https://www.edmundoptics.com/resources/application-notes/optics/cleaning-optics/

Using acetone to clean lenses is ubiquitous within the optics industry.

saxyomega90125 wrote:

DON'T USE ACETONE!!!!

First, on isopropyl alcohol... you know those Zeiss-brand wet lens cleaning cloths? Lint-free lens wipes soaked in a IPA-water solution. That's all they are. I prefer distilled water, but IPA is common.

Acetone though, now THAT is bad advice. When I got the tomahawk I take backpacking it had ugly black paint on the head that I wanted gone. Steel wool wouldn't take the paint off, my Dremel wouldn't take the paint off, dedicated paint remover of hazmat strength wouldn't take the paint off, but 14 hours in hardware store acetone and a quick buff and that paint was dust. If that isn't enough to kill your lens, the impurities will be.

And don't even touch the lab grade stuff. Forget about price - I have worked with it in the lab, and I have seen the burns and inhalation issues it will give you if you are careless.

Acetone is just fine to clean lenses, even (most) coated ones.

https://www.edmundoptics.com/resources/application-notes/optics/cleaning-optics/

In most optics shops, you will find a box of kimtech or equivalent wipes, a yellow pumper with IPA in it, and a red pumper with aceone.

Acetone is a common active ingredient in paint thinner, so it is unsurprising it could remove paint from something.  Doesn't mean it will dissolve glass or remove antireflective coatings.

It will ruin first surface aluminum mirrors though.

saxyomega90125 wrote:

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

-

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.

saxyomega90125 wrote:

DON'T USE ACETONE!!!!

First, on isopropyl alcohol... you know those Zeiss-brand wet lens cleaning cloths? Lint-free lens wipes soaked in a IPA-water solution. That's all they are. I prefer distilled water, but IPA is common.

Acetone though, now THAT is bad advice. When I got the tomahawk I take backpacking it had ugly black paint on the head that I wanted gone. Steel wool wouldn't take the paint off, my Dremel wouldn't take the paint off, dedicated paint remover of hazmat strength wouldn't take the paint off, but 14 hours in hardware store acetone and a quick buff and that paint was dust. If that isn't enough to kill your lens, the impurities will be.

And don't even touch the lab grade stuff. Forget about price - I have worked with it in the lab, and I have seen the burns and inhalation issues it will give you if you are careless.

i wouldn't use that stuff on my canon and zeiss lenses no matter what! my tolerance limit is a damp microfiber cloth and cleaning my lenses with it, as i have noted in my OP. damp cloth has worked for me forever and i won't try anything else even if labs use these awful solvents!

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."