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#26 Brianm14

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Posted 18 May 2022 - 09:11 PM

Jim,

I think such aged, perhaps dated, advice is problematical.  Lenses have changed (new coatings and cements), too, and who knows how old the advice was when it was originally cited from Leitz.

 

If I can find the time, I’ll see if I can search, and if need be, post about this in either the Quekett Microscopical Club or with The Royal Microscopical Society, by far the two preeminent microscopy organizations in the world.  All I can recall seeing anywhere I unquestionably trust favored mild interventions.  Zeiss, for instance, is cautious even about lens paper!  However, I’ve never asked.

 

The ammonia/peroxide approach still seems needlessly radical to me.  Maybe as a last resort.  I still keep asking, “Why these two particular chemicals in a mixture?”

 

CS and CL,

 

Brian



#27 jkmccarthy

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Posted 19 May 2022 - 01:49 AM

I hear you, Brian, and I don't disagree.  But here in the Classic Telescopes forum, it may be worth noting that often we are most interested in how to go about cleaning lenses (including coated lenses) that are themselves 40+ years old in many cases, so compatibility with "new" coatings, glass types, and cements is not necessarily a concern nor a requirement.   But obviously if limitations exist relative to the latest optics, those need to be appreciated and publicized as caveats !   (Generally speaking, I would expect today's premier coatings to be much more impervious than the vintage coatings of yesteryear, although granted this may not be true in all cases especially if/when cost or performance is prioritized over durability in harsh environments).

 

Since my understanding of chemistry is slim for starters, and rusty from lack of exercise to boot, I wanted to pass along thanks for pointing out the two different interpretations of percent (%) relative to hydrogen peroxide (and ammonia as well for that matter).   Here is the most applicable web content I could find on the subject of pH of hydrogen peroxide of various dilutions:

 

https://www.usptechn...h2o2-solutions/

 

I latched onto this summary statement near the bottom:  "Consequently, it is not possible to state with any certainty the pH of commercial H2O2 solutions. However, it is likely that the apparent pH will be pH 4-5 for the more dilute products (3-10% H2O2) and pH 1-4 for the more concentrated products (35-70%)."   ... while noting this summary used the terminology "apparent pH", given that the enumerated influence factor #1 mentioned earlier on the page suggested the "real pH" could differ by at least a -1 adjustment term, which is how I arrived at an estimated pH of near 3 for "household" (hair bleaching) peroxide.   But if my reasoning is flawed, please correct me ... and similarly as regards the pH of "household" ammonia.

 

In terms of achieving a more pH-neutral solution, I'd be interested to know if there may be a more optimum NH4OH : H2O2 mix ratio (by volume) than the 1:1 ratio that i see cited most often, but I appreciate the difficulty in answering this question without accurately knowing the ingredient specifications (the individual concentrations and the individual pH values prior to mixing).

 

Thanks,

 

        -- Jim


Edited by jkmccarthy, 19 May 2022 - 01:55 AM.

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#28 deSitter

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Posted 19 May 2022 - 05:02 PM

Pardon me for repeating myself - but is the culprit here coatings that are not smooth? Is that what the fungus gets a foothold on?

 

-drl



#29 Brianm14

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Posted 21 May 2022 - 01:47 AM

Here are some notes on cleaning and caring for optics and addressing problems.  It is quoted from what I consider to be the best current authoritative reference on microscopy. It is the “bible” for our current generation.  Please do not copy and re-post ANY portion without giving proper attribution.  

 

Note that the microscope is the most common scientific interest in use worldwide, and that their are many, many more profession microscopists than professional astronomers; while the reverse is true for amateurs in each field.  The RMS has for well over 100 years set the mechanical and optical standards for all microscopes, and I cannot think of an astronomical organization with with equal universal authority.  If you use a standard-size microscope slide or a coverslip, or find that your objectives or oculars can be exchanged, thank the RMS.

 

 

—Exerpted from:  Understanding Light Microscopy (RMS - Royal Microscopical Society), 2019, by Jeremy Sanderson

 

“All microscopists have their own method of cleaning which they swear by. It is paramount not to scratch the delicate anti-reflection coating that covers the front surface of the lenses of both objectives and eyepieces. Poor cleaning practices can easily make things much worse. Forming a microscopic grit from dirt and cleaning solvents can ruin both glass surfaces and anti-reflection coatings; caustic solvents can also ruin these coatings and dissolve the cement holding lenses in place. Therefore, cleaning should be done sparingly and with care.”

“Use only specialist lens-cleaning tissues for cleaning any optical surface. Disposable boxed tissues (e.g. ‘Kleenex’, ‘KimWipes’ or similar) contain wood pulp and–in some cases–silica particles, and so are exactly analogous to using abrasive sandpaper in the toilet or bathroom for personal hygiene. They will scratch and ruin delicate anti-reflection coatings. Zeiss specifically recommend Whatman Lens Cleaning Tissue 105, now made by GE Healthcare Lifesciences. As the advertising blurb says, ‘Lens Cleaning Tissues are very soft, high-absorbent, strong, chemically pure, and free from silicones and other additives. Only 0.035 to 0.040 mm thick, they ensure safe removal of surface moisture and grease without leaving fibres’. A systematic approach will aid cleaning with the minimum risk of ruining objectives: locate dirt; inspect the surface; and clean the lens surface. Wearing gloves when cleaning is down to personal preference. Some people take the view that gloves prevent contamination from the hands; equally, they can protect the hands from solvents. Ensure that you select a brand of glove that is talc-or powder-free. Locating dirt Partially rotate each component (e.g. eyepieces) in turn. Partly swing the objective off-axis, or carefully part-rotate it on its thread on-axis. Likewise, a CCD camera can be rotated on its thread. Check the condenser by moving it up and down with the substage control and moving the top lens out of the field of view. Slide DIC prisms and filters in and out of the light path. Dirt will follow the direction of movement. The only exception to this is that dirt on a CCD camera faceplate will remain static on the monitor.”

Cleaning Procedure
Begin by blowing off any dust with a dry ‘air duster’. I prefer to use a hand-operated bellows ball rather than a canister with propellant, since if the can is inverted, an invisible film of aerosol propellant can coat the objective. Resist the tendency to blow particles off with your breath. The saliva mist, together with the pre-existing dirt, and any particles from your mouth will form an abrasive micro-slurry that will cause more harm than good.

 

Never dry wipe an objective, since there is even a risk that dry lens tissues may cause scratching. Always use them dampened with a suitable solvent. However, it is possible to use an ordinary disposable tissue to wipe excess oil off the objective mount surrounding the front lens, provided that you take care not to touch the lens element itself with the tissue. This leaves much less oil in place to be cleaned off at the next step. Clean objectives by placing them face upwards screwed into the lid of their storage pot, and draw across a single lens tissue wetted with solvent. There is no need to press onto the surface of the lens when doing this–you are not window-cleaning. Repeat a couple of times with fresh tissue, and let the solvent clean off the oil. With a bit of practice, it is possible to use two or three separate areas of one piece of lens tissue to do this. However, it is best to use one piece of lens tissue only once.

Clean oil-contaminated dry objectives with a clean cotton bud; soak the tip in solvent, and wipe out the excess oil. Repeat with an unused, freshly wetted cotton bud. Take care to use real cotton buds, not synthetic ones made of polyester. This latter can dissolve in solvents used for cleaning and end up smearing the objective with a ‘glue’ that will be difficult to remove.

 

 

Clean eyepieces with a cotton bud or cotton wound onto an applicator stick. Clean from the centre outwards and not in a zig-zag motion across the eye lens surface. This latter action is likely to sweep the dirt around to another location on the lens. Neither the lower field lens nor the internal surfaces of the eyepiece should require cleaning, and the eyepiece should not be dismantled.

 

 

Filters (e.g. in fluorescence filter cubes) should not need cleaning, since they are housed within the body of the epi-illuminator. However, if they do need cleaning, clean the outer surface of the circular excitation and emission filters as for eyepieces, bearing in mind that the anti-reflection coatings will be much more delicate than those of the eye lens of the eyepiece. If you do need to clean the dichromatic mirror, tape a thin piece of card (or the flat metal key used to unscrew the filters from the fluorescence filter block) edge onto the bench, so that it protrudes a few millimetres and provides a ‘stop’ for holding the dichromatic mirror (this is shown in Figure 15.12). Lay down a few sheets of lens tissue, place the mirror on these up against the stop and clean the surface by dragging a fresh piece of lens tissue, wetted with ethanol, across the top surface of the mirror.

 

 

Differential interference contrast (DIC) sliders should only very rarely need cleaning, since they are normally located within the microscope stand for much of their lifetime. If they do need cleaning, do so with ethanol or a mild surfactant, such as Tenside solution. Do not use organic solvents, such as acetone. With microscopes fitted with CCD cameras, any dirt on the CCD faceplate is difficult to remove. It is highly likely that in removing one dirt particle, another will be introduced. Therefore, approach cleaning with extreme patience and care, or otherwise call in an accredited service engineer. Only attempt to clean those CCD cameras whose faceplate sensor is protected by a filter or glass window.

In some cameras, the sensor surface is directly exposed within the camera body and is highly likely to attract dust and other debris. This should be left to a trained engineer, in order to avoid direct mechanical and static charge damage to the CCD faceplate. If the dirt cannot be blown away, wind fresh cotton wool onto a long applicator stick, then wind on a strip of lens tissue, and use this. Wet the lens tissue and remove the dirt. Take great care to limit the pressure put on the window surface. Wind a fresh piece of lens tissue onto the applicator stick for each cleaning attempt.

The best way to clean non-optical parts of the microscope is to use a soft, slightly water-dampened cloth. If you do use a solvent, test it first on a tiny part of the rear surface of the stand! Do not use an organic non-polar solvent such as xylene, chloroform or acetone, because they tend to attack paint and some may attack the metal surface. Xylene is carcinogenic and since it is oily, will leave a greasy residue on the surface of the glass once it has evaporated. Sometimes surfaces may be contaminated with sticky organic compounds. These will usually clean very well with a cloth dampened with any alcohol. Cover your microscope when it is not in use. A microscope that remains unused for any length of time can accumulate dust and debris from the air.

 

 

 Fungal contamination [boldface added] will occur in tropical climates. This is seen as cloudiness in the image and on the objective lens. Fungal hyphae grow on the lens surfaces and also penetrate between the lens elements. It is impossible to get rid of them, and contaminated objectives and optical components can only be thrown away. Covering the microscope can exacerbate fungal contamination, and in this case the microscope should be kept in a dry, air-conditioned room and/ or kept under an infrared lamp or at low temperatures during periods of high humidity.


Microscope parts that are lubricated with grease can become stiff with age, and trying to move them will cause mechanical damage. Lubricants by Nye (Nyogel 795A; Reference 3) are recommended. Only lubricate moving parts of the stand; never lubricate optical components. Never apply an oil-or grease-based lubricant to a surface lubricated with graphite, or vice versa. Doing so will very effectively seize up the working part. In this case n-hexane should be used to dissolve the solidified grease.

 

 

If metal surfaces become jammed, then a very small amount of a light penetrating oil, such as WD-40, can be painted on and allowed to seep into the joint. Cleaning solvents Methanol, ethanol and propan-2-ol are polar solvents and are generally safe for lenses, providing they are used sparingly. I use 85% petroleum ether as a solvent (this is an n-hexane, a light petroleum fraction) with 15% propan-2-ol, as recommended in the Zeiss publication ‘The Clean Microscope’.

Some people do not recommend n-hexane for heavy use or frequent use, preferring instead filtered methanol or methylated spirits. This was the practice of two of the best Zeiss service engineers I ever met. Otherwise, use absolute ethanol-ether (30–70%), or propan-2-ol (isopropyl alcohol). Do not use the ‘rubbing alcohol’ form of propan-2-ol; this contains too much water. I find that any solution with ether is volatile, and its smell can cause headaches. Since ether is also highly flammable, I avoid it.

 

 

Ordinary glass slides can be cleaned very effectively by the green version of ‘Mr Muscle’ Window & Glass cleaner, which does not contain ammonia but uses vinegar. You are advised not to use it for objectives or other optical components–although some people do. Do not use proprietary window cleaning fluids (e.g. ‘Sparkle’, ‘Windex’), since these contain ammonia. Older lenses mounted with Canada balsam will dissolve in most aromatic solvents, and these should be avoided. Instead try using a high vapour solvent (e.g. ether) sparingly on a cotton bud.

Some optical components are surrounded by black anti-reflective lacquer. These can be damaged by organic non-polar solvents such as acetone, which can also damage plastic parts and the rubber eyepiece cups.

 

 

Cleaning summary
Remove oil before it dries onto, or seeps into, the objective. Use specialist lens-cleaning tissues–do not use general wipes. Use each tissue on a one-use basis. Then discard. Use a hexane-based solvent. Non-polar solvents can do damage. Take care not to scratch delicate optical surfaces and coatings.

 

 

References
Zeiss. ‘The Clean Microscope’. https:// bit.ly/ 2KEbdS8. Also at: https:// bit.ly/ 2KEHJUj and   Zeiss campus on cleaning. http:// zeiss-campus.magnet.fsu.edu/ articles/ basics/ care.html.

Advice on microscope lubricants (Ian Walker, Microscopy UK, 2004). https:// bit.ly/ 2OnOwE9. Micro-Tools (Europe). http:// www.micro-tools.com. Appendix”


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#30 LukaszLu

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Posted 21 May 2022 - 10:15 AM

My proven fungus tip: Before you start reaching for the chemicals, try warm running water and plain soap. I have found that this has a much better effect than, for example, isopropanol and removes the fungus that cannot be removed by other methods. Gently soap the surface with the tip of your little finger and rinse - repeat a few times. After the entire operation, I check the surface with a magnifying glass and repeat again if necessary.

 

It is worth remembering that anti-reflection layers on Unitron optics are usually very delicate. The presence of the fungus often leaves a permanent mark on them - nothing can be done about it.


Edited by LukaszLu, 21 May 2022 - 01:44 PM.

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#31 Brianm14

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Posted 21 May 2022 - 04:40 PM

My proven fungus tip: Before you start reaching for the chemicals, try warm running water and plain soap. I have found that this has a much better effect than, for example, isopropanol and removes the fungus that cannot be removed by other methods. Gently soap the surface with the tip of your little finger and rinse - repeat a few times. After the entire operation, I check the surface with a magnifying glass and repeat again if necessary.

 

It is worth remembering that anti-reflection layers on Unitron optics are usually very delicate. The presence of the fungus often leaves a permanent mark on them - nothing can be done about it.

Great post!  

Excellent!  Bravo,   Thank you!   Very well said!!!!  It is that simple!

 

My only suggestion is to never use “soap.”  Use a small, highly diluted form of a mild detergent (washing up liquid) such as Dawn in water.  Rinse, examine, repeat if necessary.  If fungal damage has been done it is irreparable and permanent.


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#32 LukaszLu

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Posted 21 May 2022 - 05:11 PM

You're right. It's quite possible that the additives found in some types of soaps might have some kind of impact on the old types of anti-reflective anti-glare coatings. The less chemicals, the safer! I reach for soap rather because of my laziness :-)


Edited by LukaszLu, 21 May 2022 - 05:12 PM.

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#33 Brianm14

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Posted 21 May 2022 - 06:16 PM

drl:  Fungi will get a foothold on even on surfaces which seem smooth and polished to us.  A billiard ball seems highly polished, that is, until we examine it under magnification.  I sincerely doubt this is an issue for fungi, which will quickly increase the roughness through chemical attack.

 

Jim:  Once you depart from the stipulated 1:1 ratio by volume of hydrogen peroxide:ammonia, one has to ask if we are then even dealing with the same chemical mixture for which such success is claimed.

 

The Monograph of the United States Pharmacopeia USP) for pharmaceutical hydrogen peroxide is as follows (The “USP Technologies”you cite is a commercial entity and has nothing whatsoever to do with the real USP, which is a non-profit quasi-governmental,  governing body which specifies purity standards for many pharmaceutical chemicals.):

———- - - 

Hydrogen Peroxide Topical Solution
H2O2 34.01

Hydrogen peroxide.
Hydrogen peroxide [7722-84-1].

» Hydrogen Peroxide Topical Solution contains, in each 100 mL, not less than 2.5 g and not more than 3.5 g of H2O2. It contains not more than 0.05 percent of a suitable preservative or preservatives.

Packaging and storage— Preserve in tight, light-resistant containers, at controlled room temperature.

Identification— Shake 1 mL with 10 mL of water containing 1 drop of 2 N sulfuric acid, and add 2 mL of ether: the subsequent addition of a drop of potassium dichromate TS produces an evanescent blue color in the water layer which upon agitation and standing passes into the ether layer.

Acidity— To 25 mL add phenolphthalein TS, and titrate with 0.10 N sodium hydroxide: not more than 2.5 mL is required for neutralization.

Barium— To 10 mL add two drops of 2 N sulfuric acid: no turbidity or precipitate is produced within 10 minutes.
Heavy metals 231— Dilute 4 mL, previously shaken, with 20 mL of water, add 2 mL of 6 N ammonium hydroxide, and gently boil the solution until the volume is reduced to about 5 mL. Dilute with water to 25 mL: the limit is 5 ppm.
Limit of nonvolatile residue— Evaporate 20 mL, previously shaken, on a steam bath to dryness, and dry the residue at 105 for 1 hour: the weight of the residue does not exceed 30 mg.

Limit of preservative— Extract 100 mL of well-mixed Topical Solution in a separator with a mixture of 3 volumes of chloroform and 2 volumes of ether, using 50 mL, 25 mL, and 25 mL, respectively. Evaporate the combined extracts at room temperature in a tared glass dish to dryness, and dry over silica gel for 2 hours: the residue, if any, weighs not more than 50 mg (0.05%).

Residual solvents 467: meets the requirements.

(Official January 1, 2007)

 

Assay— Pipet 2 mL of Topical Solution into a suitable flask containing 20 mL of water. Add 20 mL of 2 N sulfuric acid, and titrate with 0.1 N potassium permanganate VS. Each mL of 0.1 N potassium permanganate is equivalent to 1.701 mg of H2O2.

-  - - - - 

 

In the pharmaceutical plant where I once worked in microbiology quality control, assuring the sterility of materials for injection, we ran these sort of chemical tests on every new batch of each USP chemical we received.

 

Given this information I cannot tell you the pH or buffering power (that is, the capacity to resist changes in pH of the hydrogen peroxide.   In a laboratory, I would simply titrate known volumes of the hydrogen peroxide solution against known volumes of a particular strength of ammonia solution, and record the pH changes.  A curve of volumes would then generate a pH curve.  As indicated above, the H2O2 solution is surely formulated as weak acid (a specific term) for stability.  The ammonia is a known strong base.

 

Older lenses will certainly display different resistances compared to modern lenses.   Today’scements are much more solvent resistant.   Perhaps the coatings are, too.

 

I may replace my broken small pH meter and run some simple tests, but nothing substitutes for a proper titrarion under analytical lab circumstances.

My skepticism about the safety of need for this mixture remains as strong as ever.  
 

CS,

Brian


Edited by Brianm14, 22 May 2022 - 09:47 AM.

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#34 Brianm14

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Posted 21 May 2022 - 06:17 PM

You're right. It's quite possible that the additives found in some types of soaps might have some kind of impact on the old types of anti-reflective anti-glare coatings. The less chemicals, the safer! I reach for soap rather because of my laziness :-)

Soap is also made using lye (sodium hydroxide) and is fairly alkaline.

 

Additionally, cations present in the water such as Mg++ and Ca++ which are principally responsible water the hardness of water, will form a tough, water-insoluble complex with soap -in other words, scum.  We all know how much effort is needed to remove that from bathtubs, shower stalls, and sink fixtures.  Detergents don’t complex this way with these divalent cations.

 

For these reason, as well as superior cleaning ability, soaps have largely been supplanted by modern detergents.

 

Your simple lens cleaning procedure is one I practice and wholeheartedly endorse when lens cleaning fluid and quality lens paper alone won’t work.

 

With regard to age, all of my microscope lenses are at least 25 or 30 years old and the majority were manufactured in the the 1970s and early 1980s.  So simple cleaning and fungus removing methods are very appealing.


Edited by Brianm14, 22 May 2022 - 11:43 AM.


#35 LukaszLu

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Posted 25 May 2022 - 08:05 PM

That's right. Hard, mineralized water is one of my problems - in my village we use a deep water intake. The water comes from Jurassic rocks and it is practically mineral water that I need to demineralise with special equipment. However, the concern remains, so I try to wash the optics at the end of the cleaning not only with distilled water, but also with isopropanol. I treat the latter not only as a cleaning and disinfecting agent, but also as an aid in the final removal of mineral deposits from water - simply by wiping the optics with something other than water. Finally, possibly some liquid to prevent the formation of fungus, of the Baader type.


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#36 VMan

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Posted 22 February 2024 - 08:05 AM

I know this is not what exactly what this thread is about but my chief interest is in preventing fungus.

 

NE US is hardly the tropics yet after 10 years living here I noticed I get fungus in my optics everywhere. Including between lens elements.

 

Based on a used camera shop here in town where the owner literally has thousands of old optics stored in UV cabinets I was thinking for any telescope what should work is making an eyepiece sized barrel with a small UV light in it shining into the telescope, this would reach all the optical surfaces. Stored like that fungus should never be able to take hold, depending on how strong the UV light needs to be....

 

As for the smaller optics they can just go with my camera equipment in Ruggard dry box. They get exponential pricier with size... I've considering a DIY one for my telescopes... but those are all based on heat... I'm still a bit surprised that the Ruggard box controls both heat and humidity yet produces no water...

 

Does anyone have experience with storing optics in such a way to prevent fungus from occurring?

As a side note I'm also curious how this works for people who store their telescopes outside in a backyard observatory. I would assume that greatly increases the risk of fungus but then I'm not entirely sure. In the house it is always dryer than outside because of the heat... but perhaps in homes the issue of cooler basement walls with warm air is more of a culprit then an uncooled shed outside...




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