What causes cleaning marks?

[Joe Smigiel]

There are so many references to lens cleaning marks as well as a current discussion as to whether they actually impact performance (except of course on eBay where they make no difference at all to performance), but how exactly do these marks originate? Quartz has a mineral hardness of 6 and you can use powdered limestone (whiting, rottenstone, Bon Ami cleanser, etc.,) with a hardness of 3 to polish glass. Other than rubbing sand into the lens or using emory cloth (hardness 9 IIRC) or diamond dust (10), what is actually scratching the lenses or coatings? I would think cotton or other fibers would be much too soft to cause the actual damage. But, it obviously happens for some reason.

This question puzzles me almost as much as how those clothes hangers seem to accumulate without any purchase.

[David A. Goldfarb]

Old guys with trench coats, stogies, and fedoras cleaning their lenses with their polyester neckties.

[Paul Fitzgerald]

Joe,

brass rivets do wear down iron brake drums. the brass will wear down about 4X faster than iron BUT it still wears down the iron. I guess the dust wears down faster than glass or coating BUT it still wears down the glass or coating.

Just a thought

[E. von Hoegh]

Bits of abrasive material on/in whatever you are cleaning you lens with OR bits of abrasive dust on the surface of the lens when you wipe it.

They should be called something else; say "abuse marks" as that is what they are.
It is better to keep your lens clean, than to keep cleaning it. Use a protective filter and lens caps!! I bought one lens new in about 1988. It has been cleaned a grand total of 5 times.

Edit: Optical glass can be soft when compared to, say, window glass. It really doesn't take much to mark it.

[Brian Ellis]

"Cleaning marks" is often just a euphemism used to describe almost any defect in the glass or the coating. Real damage from cleaning can be caused by any number of mistakes, such as using an abrasive cloth, using a cloth with extreme dust or similar particles on it, trying to clean a lens without first removing any abrasive materials that are on it by blowing them off, cleaning the glass too often, applying too much pressure to the glass/coating, all sorts of things like that.

[IanG]

Some optical glass is actually quite soft. The glass used fot Leica Summar lenses is some of the worst, which is why you find very few good unscratched Summars.

Early coating also sometimes softened the glass surface too, while most modern Multicoating tends to form a harder tougher surface. There are no hard and fast rules.

Cleaning a lens with a dry tissue or wipe can cause minute scratches that build up over time, the liquid cleaners are often far less abrasive as well as being more effective. One problem with cleaning "dry" is that often the dust & dirt builds up at the edge of the glass, over the years this can become quite thick and hard, so much so that one lens I bought with a camera was described as having separation. In fact a good "wet" clean showed that the problem was actually 70 years of dirt.

The only lenses I've had that suffer from cleaning marks were both new enlarger lenses, and used in a commercial darkroom, I wasn't the only person to clean those lenses, I have no idea what employees used to clean then but they have a lot of fine scratches, I've only kept them for parts.

Ian

[aduncanson]

Old guys with trench coats, stogies, and fedoras cleaning their lenses with their polyester neckties.

Yes, I have heard that cigar or cigarette ash makes an effective, very fine, abrasive.

[Ole Tjugen]

... Quartz has a mineral hardness of 6 and you can use powdered limestone (whiting, rottenstone, Bon Ami cleanser, etc.,) with a hardness of 3 to polish glass. ...

Quartz has a hardness of 7, by definition. Even the hardest glasses reach only 6.5, which is easily scratched by quartz which is a common constituent of dust.

[Joe Smigiel]

Oops. My bad. How could I forget this?

Must have lost my apatite.

[vann webb]

There are so many references to lens cleaning marks as well as a current discussion as to whether they actually impact performance (except of course on eBay where they make no difference at all to performance), but how exactly do these marks originate? Quartz has a mineral hardness of 6 and you can use powdered limestone (whiting, rottenstone, Bon Ami cleanser, etc.,) with a hardness of 3 to polish glass. Other than rubbing sand into the lens or using emory cloth (hardness 9 IIRC) or diamond dust (10), what is actually scratching the lenses or coatings? I would think cotton or other fibers would be much too soft to cause the actual damage. But, it obviously happens for some reason.

This question puzzles me almost as much as how those clothes hangers seem to accumulate without any purchase.

Wear from abrasion behaves in a way that is counterintuitive to what you would expect to happen. I build machinery for a living and wear from sliding surfaces is always a source of concern especially in conveying applications. When two surfaces are in contact and an abrasive condition exists between them, the harder surface always wears first. This is because the abrasive material embeds or adheres more to the softer material turning it into a sort of sandpaper if you will. I have seen conveyors where the soft plastic chain has worn almost completely through 1/4" thick steel. Happens all the time. Studies have been conducted by major conveyor belt manufacturers that confirm this, bizarre as it sounds. The same thing happens with the lens surface. The soft cleaning surface picks up the abrasive dust and scratches the lens surface. Thus ends today's obscure lesson on abrasion.

[Glenn Thoreson]

What causes cleaning marks, you ask? Why, the photographer, of course. :D

[Bernard Kaye]

At "RAMON'S," a long ago Palm Beach, Florida marvelous photo shop, I watched a woman smoker exhale, saw the plume and watched as a bit of fiery ash descended on center of front element of a pristine Leitz coated 50mm. Summicron f 2.0: I blew it off just in time, no discernable damage, no cleaning marks; do not let a smoker near your photo gear or where your meals are being cooked or prepared. I was lucky on this one. Bernie

[lenser]

Interesting thread and it brings up two more questions.

First, I try to only use Kodak lens cleaning tissue (when I can find it). Are there any other recommended tissues out there? I'm a bit leery of the advertised soft cloths since I wonder how much junk can build up on them over time that might then cause abrasion.

Second is the tissue's counterpart, lens cleaning fluid. I can no longer find the old Kodak fluid which I though was great. Everything else I've found seems to leave wipe marks or a residue which I then want to rub away which means putting real force into the tissue. I am guessing that doing that could actually cause abrasive cleaning marks. Can someone please tell me if the Kodak stuff is still out there and recommend GOOD alternatives if it's not?

By the way, most of my cleaning is now done carefully with a lens pen in the rare occasion when I finger mark a lens, but I do occasionally come up with an old user from garage sales, auctions or the big "E" which need more radical treatment.

Thanks.

Tim

[Peter K]

Tim, there is a recommendation given by Zeiss to clean lenses: First clean the lens with a degreased brush to remove any solid matter. Than you can wipe the lens with an often washed soft cloth together with freshly distilled water. This can easily be made by breathing on the lens.

Lens cleaner will only be used with real dirty lenses. Also surgical spirit or ether can be used. But never alcohol, because alcohol can solve the lens cement.

Of course the best is to avoid cleaning by using lens caps.

Cheers
Peter K

[lenser]

Thanks, Peter. I do keep caps on the lenses when practical or available. I'm a bit cautious of the breath on the lens thing because of some arcane info I found years ago. Brass instruments can be corroded on the inside from secretions (saliva and humidity) from a player who uses lots of mints or otherwise indulges in sweets like sodas and candy bars. Apparently the sugars can react with the metals to increase corrosion.

It's probably overkill, but I enjoy soft drinks and use mints and I'm concerned about even the most casual effect on coated lenses.

Tim

[Christopher Hansen]

Interesting thread and it brings up two more questions.

First, I try to only use Kodak lens cleaning tissue (when I can find it). Are there any other recommended tissues out there?
Tim

I think the same paper is now being sold by Tiffen. The paper looks and feels the same, but the package is gray instead of Kodak yellow.

[Alan Davenport]

Cleaning marks can ONLY be caused by someone cleaning the lens. Any marks that are not caused by cleaning are, by definition, NOT cleaning marks.

Glad to help...

[seawolf66]

Do these new micro cloths help elemanite rub marks or are rub marks more by rubbing to hard!

[David A. Goldfarb]

Microfiber cloths are good to remove oil or fingerprints, as long as the lens is dusted first. The cloth won't scratch the lens, but rubbing the dust around can.

For high-end cine lenses, polishing and recoating seems to be a fairly common practice.

[E. von Hoegh]

Microfiber cloths are good to remove oil or fingerprints, as long as the lens is dusted first. The cloth won't scratch the lens, but rubbing the dust around can.

For high-end cine lenses, polishing and recoating seems to be a fairly common practice.

I beg to differ. Oily or fingerprinty guck can and will hold grit, and must be "washed" off with a moistened tissue and NO pressure.

Moisten the tissue, and move it around the surface relying on the tissue's own "elasticity" for pressure. Never press through the tissue.


As I stated, and as several have iterated and reiterated, "it is better to keep your lens clean, than to keep cleaning it" Use the lens caps. Use a sacrificial filter.


As I posted on the last page; I have one lens I purchased new in the '80s. It has been cleaned about 5 times.