Can delamination of optics be prevented in 'vintage optics'?

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charlie g
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Can delamination of optics be prevented in 'vintage optics'?

#1 Post by charlie g » Mon Nov 20, 2017 5:49 am

Hi all..I am quite pleased with my : Plan 2X objective. Always I am curious for a : 1X plan...or...gulp...1X plan-apo objective. The high e-Bay price of : 1 X quality objectives...stops me from a purchase . Well today I enjoyed e-Bay visit to a seller with a: 'Carl Zeiss Plan 1.25 X/ 0.04 NA, 160 TL objective'..." excellent optically, without delamination or other imperfections".


My question to all forum microscopists is: If no delamination is afflicting an objective, or ocular...can sensible care for these items prevent delamination from occurring?

I am sincere in requesting comments on this matter. I enjoy so many older stands, so many older books, so many older oak furniture family members...I sense I know how to care for these aspects of our home.

If a Carl Zeiss objective has: no delamination...., can I myself keep this optical component with no chance of delamination occurring? Does: delamination occur for no reason/ 'out of the blue'?

thanks all, for coments. Charlie guevara

apochronaut
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Re: Can delamination of optics be prevented in 'vintage optics'?

#2 Post by apochronaut » Mon Nov 20, 2017 1:25 pm

That's a very interesting question Charlie. I have pondered it quite a bit because I have had the privilege of having had many bad objectives pass through my hands. Currently, I have a box full of them, awaiting their fate of either a respectable repair or a dis-respectable disposal.

From my experience, which covers a large amount of Spencer and AO optics, relatively less Bausch & Lomb or Leitz , less Zeiss( due to avoidance), plus a few scattered other brands; the problem can be classified according to the way it manifests itself and therefore one can either avoid or mitigate it somewhat. It manifests itself differently from manufacturer to manufacturer, from cementing material to cementing material and tends to occur in batches.

The first thing is, it helps to identify what the cementing material is because depending on that, the problem will be different. Up to a certain point in time, and it obviously varies according to the manufacturer, all of the cement was Canada Balsam. Most makers had some problems with Canada Balsam but the problems vary in their severity and form. I think there are 3 basic problems with it and doubt if there is anything one can now do to halt the most common one, drying out. First, there is contamination. This is what causes the previously referenced batching of de-lamination , where objectives of the same type, suffer similar de-lamination in the same element or elements, while other elements or objectives in the series do not . Usually there is a milky swirly type of film throughout the cement, probably due to some chemical reaction taking place over time. If that hasn't happened by now, then it probably isn't going to. Second, there is the effect of airborne chemicals, or mild airborne solvents , that enter from the exterior and cause a kind of circumferential breakdown, from the outside in. Again, it probably happened in the past , when many facilities did not have the best ventilation conditions or non at all. The problem is probably not going to get any worse. This can mimic the third problem, the outright drying out of the cement. In drying, the balsam will develop anything from air bubbles, to cracks and crystals and yellowing.
I have had some success in re-dissolving the balsam with ethanol, and healing most of the above problems, even to the point of getting a perfect result but how long it will last is another question. If it lasts as long as the original...50 years or so, then I guess it is a good enough job. The good thing is, that most of the objectives cemented with balsam and currently in good condition will probably stay so, for a considerable period of time. Keeping them in a cannister when not in use helps reduce drying because balsam can overdry and crack but if the lenses are in good shape now, after 50 years, then probably they are sealed into their location sufficiently, to resist drying. Some makers edged cemented lenses with a sealant.

With synthetic cements, which mostly arrived from the 50's on, the problem is more complex. The problems seem similar in appearance, though , to those associated with balsam minus the yellowing. Bausch & Lomb had some problems , which appear on the surface to mimic the problems with balsam quite closely but the solvents required to heal the problem are pretty heavy duty; methyl iodide and the like. I have also had some success with mild heat( boiling water), and have evolved some pretty low tech , novel methods of clamping lens doublets. B & L's problems seem to occur in batches, so my guess is that they got into some cement that was mis-manufactured. Either that, or their preparation and curing at the production level went off the rails. It does seem that in this case, the problem showed up quickly, so an objective unaffected, is unlikely to be affected any time soon. I have duplicates of B & L objectives, with some de-laminated and others, not. The good ones show no sign of deterioration over 15 years or so. Generally, most of the synthetic cements used have been pretty good. They don't seem to suffer from drying as much as balsam but then , there are fewer years since their adoption too.

Then there is the problem of the effect of light and heat. If you took 20 objectives from a production that later showed to have a disproportionately high rate of failure and put 10 into use, up to the point of where some failed but had another 10 sitting on a shelf wrapped in tissue paper, would the failure rate be statistically similar? I don't think so. Firstly, some objectives, probably have a tendency to concentrate heat in certain elements. It may be a small amount but it is there. Secondly, there must be an effect of certain wavelengths of light upon the chemistry of the cement. There does seem to be some evidence that an unused objective has less of a chance of having cement problems, than one that has been used.

So; the general rules might be; avoid conditions that promote drying and don't leave an objective in position over a light source if not being used and avoid excessive intensity where possible. I don't think there is too much else, one can do to avoid the problem, which ultimately seems to be mostly a manufacturing defect: crappy cement, poor homogenization and or curing. I have objectives that are over 100 years old, that have been used to the point of the knurling being worn off and barely visible, and they have impeccable glass in them.

MicroBob
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Re: Can delamination of optics be prevented in 'vintage optics'?

#3 Post by MicroBob » Mon Nov 20, 2017 8:49 pm

I try to save optics to some extent from sudden temperature changes by covering microscopes with a hood when not in use. I try not to have optical parts on the desk when not in use. My microscopes live in a big closed cupboard apart from the one that is in use. I swear to become a tidy person and begin to store optical parts in padded compartments so they cant bounce against each other. As apochronaut wrote, switch the light off when not in use. That is probably all that can be done under practical conditions.

charlie g
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Re: Can delamination of optics be prevented in 'vintage optics'?

#4 Post by charlie g » Tue Nov 21, 2017 4:01 am

Thank you Phil and Bob for your optics best practices, and for overview of the variety of delamination processes. I love our collections of light optics! Charlie guevara

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Re: Can delamination of optics be prevented in 'vintage optics'?

#5 Post by zzffnn » Tue Nov 21, 2017 3:04 pm

Apo,

Please kindly elaborate about "I have also had some success with mild heat( boiling water), and have evolved some pretty low tech , novel methods of clamping lens doublets."

I can use your advice for a newly glued 4 element achromat 5x loupe. There is white film close to edge and in between elements. Seller is a nice and honest person. He said he will cover all exchange cost, though mild heat may remove the white film (he asked me to try mild heating with a blow dryer first). He also indicated that they glued those 4 new elements right after my payment and probably did not let them dry/cure long enough.

I have not tried blow dryer. What is your advice on this? Thank you.

apochronaut
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Re: Can delamination of optics be prevented in 'vintage optics'?

#6 Post by apochronaut » Tue Nov 21, 2017 3:31 pm

Most of the cemented lenses I have attempted repair on, are assessed on the basis of some knowledge of cement type, lens mount, or previous experience with another similar lens. You have an existing relationship with a person who has clearly sold you a mis-manufactured product. This lens, appears to be new, so I would think that the loupe should be replaced by the maker, with one in perfect condition. Is there some reason you would attempt repair, rather than replacement?

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zzffnn
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Re: Can delamination of optics be prevented in 'vintage optics'?

#7 Post by zzffnn » Tue Nov 21, 2017 3:34 pm

I am just thinking it may be worth a try (may be an easy fix?), since there is almost no risk (he will take it back if I fail).

smollerthings
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Re: Can delamination of optics be prevented in 'vintage optics'?

#8 Post by smollerthings » Fri Sep 10, 2021 2:45 pm

apochronaut wrote:
Mon Nov 20, 2017 1:25 pm
I have had some success in re-dissolving the balsam with ethanol, and healing most of the above problems, even to the point of getting a perfect result but how long it will last is another question. If it lasts as long as the original...50 years or so, then I guess it is a good enough job.
apochronaut, I have some delamination issues on a 60x LOMO objective lens. Could you elaborate how you healed it with ethanol? Thanks!

AntoniScott
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Re: Can delamination of optics be prevented in 'vintage optics'?

#9 Post by AntoniScott » Sun Sep 26, 2021 1:40 pm

Could it be that glass changes or corrodes ovetime ? My microscope collection consists of several newer scopes (1970's or 1980's) for my everyday work as well as vintage scopes for show only.
Low power visual inspection of the inside lens elements sometimes show surface degradation. Other similar objectives show optical differences with no physical differences of lens surfaces. It seems that the newer objectives have less image quality problems.

My oldest microscope, a Seibert, considered the precursor to Leitz, is definitely "vintage". Low power stereo examination of the objectives inner and outer surfaces have revealed some surface issues of unknown origin or cause that have affected the image quality in two of the three objectives. Since these microscopes are ony for display, it is not of great concern. I seem to think, without knowledge, that the glass changes over time. I see microscopic lines on the surface.

I have three other inexpensive microscopes that I collected from the late 1950's with the Lafayette Radio brand name on them, a 900X and a 1200x that all suffer from some apparent degradation of the image quality. Although these microscopes appeared to be in perfect condition, it seemed that the glass had undergone some disintegrating of the surface. Does glass break down with age ?

The last microscope from the 1950's , a 1500x Lafayette, (100x oil x 15x eyepiece) was a higher quality scope with standard size objectives. The 5x has some clouding but the 10x and 40x are excellent optically.The 100x oil shows some degradation.

These are microscopes in my collection for sentimental value, :D so I'm not concerned about their optical quality today since they are sixty plus years old.

Conclusion: I believe that microscope objectives lose their image quality over time. Perhaps humidity, air pollution or breakdown of element cementing may contribute to this.

MicroBob
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Re: Can delamination of optics be prevented in 'vintage optics'?

#10 Post by MicroBob » Sun Sep 26, 2021 3:58 pm

Hi Antoni,
more and diversified glass mixes were an important point in optics design. Carl Zeiss founded a cooperation with Ernst Abbe and glass maker Otto Schott because the available glasses were limiting optics development with their properties and varying quality. The most prominent outcome of this cooperation were the apochromatic objectives. Bacteriology was a very important topic at the time and supplying Robert Koch or Louis Pasteur with instruments was an important way to promote the companies products. The early apochromats were not durable, Zeiss replaced them and promised a guarantee, but their life was limited. A very common object to observe degradation are slides, often suffering from hydrolysis after just a few years.

My work objectives are from the 50s to 80s and don't seem to wear. Your objective degradation with lines on the surfae sound a lot like fungus. In many cases it can be removed without important damage.

Bob

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Re: Can delamination of optics be prevented in 'vintage optics'?

#11 Post by BramHuntingNematodes » Sun Sep 26, 2021 8:07 pm

My tip would be to not drop your objectives who knows how many delaminated objectives especially in secondary markets like ones frequented by the frugal microscopist were dropped at some.point by a drunk grad student who was too heartbroken to throw it away. A few decades later it ends up in surplus no one having.looked at since.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

apochronaut
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Re: Can delamination of optics be prevented in 'vintage optics'?

#12 Post by apochronaut » Sun Sep 26, 2021 8:36 pm

Commentary by Ernst Gundlach casts the Zeiss attempts in a dim light. Journal of the Royal Microscopical Society. Beginning in the middle of page 285.

https://books.google.ca/books?id=ZhMAAA ... ts&f=false

Chas
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Re: Can delamination of optics be prevented in 'vintage optics'?

#13 Post by Chas » Tue Sep 28, 2021 7:34 pm

It seems to be quite a strange material that ends up coating the internal glass surfaces old (garden-shed stored?) microscopes, its not dust, it doesn't seem to be oil. I think I have seen it 'explode' and spread when breathed on.
[Beck eyepieces seem to suffer quite a bit].
Sulphates? :
https://pubs.acs.org/doi/full/10.1021/ar9002009

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