Hard debris on lens element

George Mann · Feb 23, 2023

Hi. I have some hard debris on my rear lens element that appears to be bonded to it, and don't know what I should treat it with. Any suggestions?

Philippe-Georges · Feb 23, 2023

When I have some 'tough' dirt sticking on a lens surface, I use consecutively two liquids after I attempted the dry way.
First a liquid sensor cleaner with the corresponding want (which is an 'evolved' lens cleaner), and if this isn't 'strong' enough, then the famous PEC 12 liquid and a PEC lint free pad, which is actually a good film emulsion cleaner but a stronger solvent.
Always applied gently and reiterative, with fresh products, until I reach an acceptable result.
Apply the liquid on the pad/want, NOT on the lens, as it can infiltrate into the lens system, between assembled elements (canada balsam) or tubus.
When this doesn't help, then I give up because when persistently rubbing, sometimes, morde damage can be done than just some dirt sticking on the lens surface...

Be careful, do it at your own risk and good luck....

George Mann · Feb 23, 2023

I have a whole bottle of PEC 12 + pads. But I didn't know how safe this fluid is for optics.

Philippe-Georges · Feb 23, 2023

George Mann said:
I have a whole bottle of PEC 12 + pads. But I didn't know how safe this fluid is for optics.

I applied it on my Linhof-Schneider Super-Angulon 90mm lens (Technorama), and there was no problem, but don't over do it, use the minimum of liquid and go gently. First blow away the loose particles.
I also used it on a B+W filter.

xkaes · Feb 23, 2023

Don't pull out the "scalpel" just yet.

A picture of the "some hard debris" would help.

Let's start with "Is it animal, vegetable or mineral?"

Dan Daniel · Feb 23, 2023

xkaes said:
Don't pull out the "scalpel" just yet.

A picture of the "some hard debris" would help.

Let's start with "Is it animal, vegetable or mineral?"

Yep, different solvents for different junk? Sometimes alcohol (fats), sometimes acetone (some plastics), sometimes simply water, etc. A damp cotton swab to apply on the spot only. A wooden toothpick can be helpful to poke at a chunk and see if it will come away, but always poke sideways and up, not down. And presoak with something to soften bond to coating.

George Mann · Feb 23, 2023

They are hard white specs of unknown origin. Will Alcohol damage the lens?

I have some Eclipse fluid that I may try first.

Philippe-Georges · Feb 24, 2023

George Mann said:
They are hard white specs of unknown origin. Will Alcohol damage the lens?

I have some Eclipse fluid that I may try first.

It depends on the age of the lens and the way the elements are cemented, alcohol dissolves the canada balsam used to cement the optical elements, if too munch is applied and gets into the construction...

I thought that Eclips fluid doesn't contain alcohol, and, if I am not mistaking, Eclips can be used as a sensor cleaner, so it must be a rather 'gentle' product.

I don't think that the origin nor the character of the debris is so important, in this particular case, for selecting the solvent, but I have no prove for this!

Carl Zeiss offers an interesting range of products for the maintenance of optical systems, which is obvious...

Long time ago, we used C Cl4 (known as Tetrachloorkoolstof) in the darkroom, but this is so toxic (which we didn't knew) that it is forbidden now.
But it was an extremely good and very volatile solvent for thoroughly cleaning film, lenses and all other delicate materials, and not leaving any dry marks.
It was the basis of the famous Kodak lens - and film cleaners which were renown to be very effective.

xkaes · Feb 24, 2023

Philippe-Georges said:
I don't think that the origin nor the character of the debris is so important, in this particular case, for selecting the solvent, but I have no prove for this!

Since we know absolutely nothing about the lens or the "debris", everything we say is pure meaningless conjecture.

So my suggestion is "Run it through the dishwasher".

Dan Daniel · Feb 24, 2023

xkaes said:
So my suggestion is "Run it through the dishwasher".

Before this, three hours in a toaster oven will carbonize any organic debris so it washes off easier.

Philippe-Georges · Feb 24, 2023

xkaes said:
Since we know absolutely nothing about the lens or the "debris", everything we say is pure meaningless conjecture.

So my suggestion is "Run it through the dishwasher".

You would be surprised how efficient a dishwasher washes...
And how efficient a toaster oven toasts...
And how easily toasted debris washes off...
But how to avoid the dry marks left by the drying droplets on the toasted surface?

MattKing · Feb 24, 2023

I'd try a very small amount of distilled water first.
Water is an effective solvent for many things.

Dan Daniel · Feb 24, 2023

Philippe-Georges said:
But how to avoid the dry marks left by the drying droplets on the toasted surface?

Cascade Sheeting Action!!

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George Mann · Feb 25, 2023

I tried cleaning it with PEC-12. It was a complete failure.

Dan Daniel · Feb 25, 2023

Try another solvent. Alcohol might be a good one, water also. It does make a difference.

xkaes · Feb 25, 2023

Dan Daniel said:
Try another solvent. Alcohol might be a good one, water also. It does make a difference.

Yeah, especially if we had a clue as to what it might be. All we have done so far is throw spaghetti on a wall.

George Mann · Feb 25, 2023

xkaes said:
Yeah, especially if we had a clue as to what it might be. All we have done so far is throw spaghetti on a wall.

Paint or glue perhaps.

Dan Daniel · Feb 25, 2023

Wait... drinking alcohol and throwing spaghetti cooked in water on a lens hanging on the wall??? I am confused.

Acetone. Slightly damp cotton swab on top of a piece. You do not want it flowing into the edges. It evaporates quickly so do a few times. Then see if a gentle push with a toothpick will move it. Stay away from any painted or plastic parts.

xkaes · Feb 25, 2023

And sprinkle some hydroxychloroquine on it for good measure.

BradS · Feb 25, 2023

Let's try a more direct approach....
@George Mann Can you please tell us what lens has this hard debris ? Also, if you can, please post of photo the debris.

George Mann · Feb 25, 2023

I don't have enough light to photograph the hard white specs on the rear element.

The lens is a Mamiya 50mm f2.

George Mann · Mar 14, 2023

Well, lighter fluid didn't fix it. But I have been able to scratch away a bit more of this rock hard material.

Should I try acetone?

Dan Daniel · Mar 14, 2023

Alcohol. Then ammonia. Then acetone.

Damp cotton swab sitting on the spot without dripping onto rest of lens. Acetone will evaporate quickly so no sense letting a swab sit for more than 15 seconds. And keep the acetone off of painted surfaces.

George Mann · Mar 14, 2023

Dan Daniel said:
Alcohol. Then ammonia. Then acetone.

I have already tried alcohol. Why ammonia?

Dan Daniel said:
Damp cotton swab sitting on the spot without dripping onto rest of lens.

My experience with swabs tells me that I will likely fail to keep it off the lens. Should I be using a toothpick instead?

Dan Daniel · Mar 14, 2023

I meant to not have the liquid flow out and puddle on the rim or such. Getting it to touch the area around the debris is fine.

Hard debris on lens element

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