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Best solution for Cleaning old Optics?
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PostPosted: Tue Aug 29, 2023 2:34 pm    Post subject: Best solution for Cleaning old Optics? Reply with quote
I picked up a couple of lots of 1960s lenses which were in storage in a hot dry climate. May had plastic compounds in the lens bubbles or cases which appear to have offgased onto the glass. I usually have good succcess with Butane, for the deep cleanings but on this its making a smeary mess. They do clean but wondering what else to try Acetone?


PostPosted: Tue Aug 29, 2023 7:42 pm    Post subject: Reply with quote
Try meths/similar alcohol solvent first. Normally lenses and coatings are fine with either meths or acetone, or indeed most organic solvents, but in your case I would be nervous that the detritus on the lens may have affected coatings or even the lens surface. If the detritus seems oily/gungy try naphtha/coleman fuel. You could also try ether if you have some.


PostPosted: Tue Aug 29, 2023 7:48 pm    Post subject: Reply with quote
If it is from the off/outgassing of decomposing polyurethane foams and PVC case linings, try distilled water with a tiny bit of detergent first; that often works on the outgassing deposits, it won't work on the decomposing foam itself.

Of course, any cleaning liquid, apply it on a lint-free non-dyed cloth first, do not drip it directly onto the lens.

Generally I would proceed roughly in the following order from least to most aggressive, until I find something that works:

1) 100% distilled water
2) 100% distilled water + very small amount of soapy cleaner (e.g. a tiny amount of washing up liquid/detergent)
3) 70% distilled water + detergent + 30% isopropyl alcohol (safe on most surfaces)
4) 70% isopropyl alcohol + 30% distilled water (may affect some painted surfaces!)
5) 100% isopropyl alcohol (may affect some painted surfaces!)
6) naphthalene (lighter fluid) (do not get this onto any painted surfaces!)
7) acetone (do not get this onto any plastic parts or painted surfaces!)

8 ) if you can get it, ether; that's what many optics manufacturers use for final cleaning of the lens surfaces before coating.

You can try any proprietary lens cleaner solution as well, which is usually some pre-mixed combination of distilled water / isopropyl alcohol / soapy cleaner / vinegar / ammonia etc.

CAUTION 1: On 60's lenses some internal lens coatings may be soft and can be affected by any physical contact and/or contact with the above solvents. The external lens surfaces are generally hard-coated and safe for the above solvents and wiping with a lint-free cloth.

CAUTION 2: Older doublets are likely to have been cemented using Canada balsam (the resin of a specific species of pine); Canada balsam will readily dissolve in ispopropyl alcohol, acetone (and xylene for that matter), so do not let that solvent creep between the lenses!!


PostPosted: Tue Aug 29, 2023 8:12 pm    Post subject: Reply with quote
Anybody tried Limonene?


PostPosted: Tue Aug 29, 2023 9:16 pm    Post subject: Reply with quote
RokkorDoctor wrote:
If it is from the off/outgassing of decomposing polyurethane foams and PVC case linings, try distilled water with a tiny bit of detergent first; that often works on the outgassing deposits, it won't work on the decomposing foam itself.

Of course, any cleaning liquid, apply it on a lint-free non-dyed cloth first, do not drip it directly onto the lens.

Generally I would proceed roughly in the following order from least to most aggressive, until I find something that works:

1) 100% distilled water
2) 100% distilled water + very small amount of soapy cleaner (e.g. a tiny amount of washing up liquid/detergent)
3) 70% distilled water + detergent + 30% isopropyl alcohol (safe on most surfaces)
4) 70% isopropyl alcohol + 30% distilled water (may affect some painted surfaces!)
5) 100% isopropyl alcohol (may affect some painted surfaces!)
6) naphthalene (lighter fluid) (do not get this onto any painted surfaces!)
7) acetone (do not get this onto any plastic parts or painted surfaces!)

8 ) if you can get it, ether; that's what many optics manufacturers use for final cleaning of the lens surfaces before coating.

You can try any proprietary lens cleaner solution as well, which is usually some pre-mixed combination of distilled water / isopropyl alcohol / soapy cleaner / vinegar / ammonia etc.

CAUTION 1: On 60's lenses some internal lens coatings may be soft and can be affected by any physical contact and/or contact with the above solvents. The external lens surfaces are generally hard-coated and safe for the above solvents and wiping with a lint-free cloth.

CAUTION 2: Older doublets are likely to have been cemented using Canada balsam (the resin of a specific species of pine); Canada balsam will readily dissolve in ispopropyl alcohol, acetone (and xylene for that matter), so do not let that solvent creep between the lenses!!


The only thing I can fault in this advice is the description naphthalene.
Naphthalene is a pure compound (with the formula C10H10, basically two fused benzene rings) which is solid at room temperature, it used to be the active ingredient in moth balls. see https://en.wikipedia.org/wiki/Naphthalene.

Lighter fluid is one of many hydrocarbon mixtures described as Naphtha, some solvent naphthas are much better solvents (and more aggressive) than other naphthas. The naphtha we make most at work is roughly equivalent to gasoline but with a much lower octane rating.


PostPosted: Wed Aug 30, 2023 7:49 am    Post subject: Reply with quote
DConvert wrote:
The only thing I can fault in this advice is the description naphthalene.
Naphthalene is a pure compound (with the formula C10H10, basically two fused benzene rings) which is solid at room temperature, it used to be the active ingredient in moth balls. see https://en.wikipedia.org/wiki/Naphthalene.

Lighter fluid is one of many hydrocarbon mixtures described as Naphtha, some solvent naphthas are much better solvents (and more aggressive) than other naphthas. The naphtha we make most at work is roughly equivalent to gasoline but with a much lower octane rating.


Thanks DConvert, learnt something new! Like 1 small

I used to think naphta was simply short for naphtalene, but now I know better (just hope I remember it, old habits die hard!) Wink


PostPosted: Wed Aug 30, 2023 9:55 am    Post subject: Reply with quote
RokkorDoctor wrote:
If it is from the off/outgassing of decomposing polyurethane foams and PVC case linings, try distilled water with a tiny bit of detergent first; that often works on the outgassing deposits, it won't work on the decomposing foam itself.

Of course, any cleaning liquid, apply it on a lint-free non-dyed cloth first, do not drip it directly onto the lens.

Generally I would proceed roughly in the following order from least to most aggressive, until I find something that works:

1) 100% distilled water
2) 100% distilled water + very small amount of soapy cleaner (e.g. a tiny amount of washing up liquid/detergent)


Interesting you recommend just distilled water first before washing up liquid - what's the reason for that? Asking out of inexperience, I'm guessing the 1960s~ internal surfaces being soft is the reason?

If so, do you have some examples of cleaning in the past demonstrating this? I didn't know they were that soft.. or maybe washing up liquid more aggressive than I thought. I understood it as gentle.

RokkorDoctor wrote:

CAUTION 2: Older doublets are likely to have been cemented using Canada balsam (the resin of a specific species of pine); Canada balsam will readily dissolve in ispopropyl alcohol, acetone (and xylene for that matter), so do not let that solvent creep between the lenses!!


Also interesting, now letting that alcohol seep between lenses and left, I imagine an impact, but I don't have experience. How easily would it dissolve it? Of course probably working away at the edges, enough to show dreaded separation with an impact etc etc.


PostPosted: Wed Aug 30, 2023 10:35 am    Post subject: Reply with quote
Zeiss has a pretty decent guide on their website for objective caring which many of the content apply to lens cleaning too https://zeiss-campus.magnet.fsu.edu/articles/basics/care.html .

Last edited by calvin83 on Wed Aug 30, 2023 2:19 pm; edited 2 times in total


PostPosted: Wed Aug 30, 2023 1:44 pm    Post subject: Reply with quote
I use 96% denatured alcohol, apply it with a q-tip/cotton swab and clean with dedicated lens paper. I find anything with detergent leaves residue.


PostPosted: Wed Aug 30, 2023 4:56 pm    Post subject: Reply with quote
eggplant wrote:
RokkorDoctor wrote:
If it is from the off/outgassing of decomposing polyurethane foams and PVC case linings, try distilled water with a tiny bit of detergent first; that often works on the outgassing deposits, it won't work on the decomposing foam itself.

Of course, any cleaning liquid, apply it on a lint-free non-dyed cloth first, do not drip it directly onto the lens.

Generally I would proceed roughly in the following order from least to most aggressive, until I find something that works:

1) 100% distilled water
2) 100% distilled water + very small amount of soapy cleaner (e.g. a tiny amount of washing up liquid/detergent)


Interesting you recommend just distilled water first before washing up liquid - what's the reason for that? Asking out of inexperience, I'm guessing the 1960s~ internal surfaces being soft is the reason?

If so, do you have some examples of cleaning in the past demonstrating this? I didn't know they were that soft.. or maybe washing up liquid more aggressive than I thought. I understood it as gentle.

RokkorDoctor wrote:

CAUTION 2: Older doublets are likely to have been cemented using Canada balsam (the resin of a specific species of pine); Canada balsam will readily dissolve in ispopropyl alcohol, acetone (and xylene for that matter), so do not let that solvent creep between the lenses!!


Also interesting, now letting that alcohol seep between lenses and left, I imagine an impact, but I don't have experience. How easily would it dissolve it? Of course probably working away at the edges, enough to show dreaded separation with an impact etc etc.


If the contamination is easily soluble in water, there is no need for the detergent. Adding detergent can increase the risk of residue marks and unintended removal of lubricant if it accidentally gets where it shouldn't, so a bit safer to start with pure distilled water.
Also, adding detergent reduces the surface tension and increases the risk of excess water getting under the lens retaining ring, so again a bit safer to first try without detergent.

I have first hand experience of soft internal lens coatings. For a period Minolta occasionally used a soft coating on one of the internal lens surfaces. These can be found in some AUTO ROKKOR and early MC ROKKOR lenses. They are only used on the odd lens surface here and there inside a cell. The outer lens surfaces of the cells were always hard coated, so if you don't open up any lens cells there is nothing to worry about.

These soft coated Minolta ROKKOR surfaces (so far) have always been of a dull green residual reflection. There were also hard coated surfaces with a green reflection, so a green internal coating reflection on an early ROKKOR lens simply means to be extra careful if you are going to take a cell apart to clean the individual elements, because it may be a soft coating.

These soft coatings are a royal pain to clean, as even the slightest physical contact will damage them. Dragging a hair over the surface results in a scratch (not kidding!). The softest brush or microfibre cloth will ruin them. So far, I have only had success cleaning these soft coated lens surfaces by carefully submersing the element in either distilled water, isopropyl alcohol, or acetone. Sometimes a bath in one solvent followed by another one has done the trick. Finally I set the lens on its side edge onto an absorbent tissue that wicks away any solvent collecting at the bottom edge, and then I let it dry without touching the coated surface at all.

I have no idea whether these surfaces came soft coated out of the factory, or whether it is a deterioration that has happened over time to these particular coatings with residual green reflection.


PostPosted: Wed Aug 30, 2023 6:27 pm    Post subject: Reply with quote
RokkorDoctor wrote:

I have first hand experience of soft internal lens coatings. For a period Minolta occasionally used a soft coating on one of the internal lens surfaces. These can be found in some AUTO ROKKOR and early MC ROKKOR lenses. They are only used on the odd lens surface here and there inside a cell. The outer lens surfaces of the cells were always hard coated, so if you don't open up any lens cells there is nothing to worry about.

These soft coated Minolta ROKKOR surfaces (so far) have always been of a dull green residual reflection. to be extra careful if you are going to take a cell apart to clean the individual elements, because it may be a soft coating.There were also hard coated surfaces with a green reflection, so a green internal coating reflection on an early ROKKOR lens simply means

These soft coatings are a royal pain to clean, as even the slightest physical contact will damage them. Dragging a hair over the surface results in a scratch (not kidding!). The softest brush or microfibre cloth will ruin them. So far, I have only had success cleaning these soft coated lens surfaces by carefully submersing the element in either distilled water, isopropyl alcohol, or acetone. Sometimes a bath in one solvent followed by another one has done the trick. Finally I set the lens on its side edge onto an absorbent tissue that wicks away any solvent collecting at the bottom edge, and then I let it dry without touching the coated surface at all.

I have no idea whether these surfaces came soft coated out of the factory, or whether it is a deterioration that has happened over time to these particular coatings with residual green reflection.

Single-layer AR coatings (MgF2) minimize reflections at green color. If the coating has green color out of the factory, it may be coated with an extra layer of different material.
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