Microscope storage temperature

[Wes]

Summer is here and the temperature has been steadily rising so I started wondering at which point it becomes dangerous for microscopes if you don't have control over it. I've read about delamination progressing during the warm season and then ceasing as the weather gets cold so I was curious to hear your opinions about the microscope storage temperatures. Today it was 30° C in the room where I keep my microscope and I feel thats a bit too much but I might just be paranoid. I guess things like different thermal expansion coefficients between optics (lenses prisms etc) and the metal components that hold them fixed could be one source of problems but what do you think???

Wes

[wporter]

I don't think a differential thermal expansion is a problem, unless you put the microscope in an oven or other source of high heat. The bigger problem for scopes is high humidity, causing fungal growth on the glass surfaces. Some people in tropical climes use enclosures with dehumidification in which to store the scope when not being used; this could be as simple as an inverted 5-gallon bucket with some dessicant packs.

[MicroBob]

Hi Wes,
this should be no big problem unless you have a Zeiss West microscope
This topic gets a lot of attention, but there is probably little statistically relevant information available.
For Zeiss West it is the better objectives that have the most problems, like the 63/1,4 Planapo.

I recently talked to an occasional guest of our group who uses premium Zeiss equipment of the last 6 decades and earns his money with caring for microscopes. He has nearly no problem with delamination and he stated that his recipe was to keep the temperature above 20°C all the time. The thermal stress will be the same for positive as for negative temperature differences, but the glue is more flexible at higher temperatures. Hobbyst46-Doron lives in Israel and also doesn't have a problem with delamination, which would support this theory.
I myself try to do this: Keep the room above 20°C, keep a cloth cover over the microscopes all the time, limit the time the room is aired so the microscopes don't cool down a lot.
Here in northern Germany we have outside temperatures of ca. -15°C to +30°C, so it is usual to have a proper central heating system that takes care of too low temperatures. An air conditioning system is not really necessary at these temperatures, expensive and ugly. So the temperature span is already quite limited.

Delamination can also be the result of mechanical shock. So a glass work table might be a problem when an objective just tips over on its side.

Bob

[Wes]

wporter I guess humidity control would be easier to achieve than temperature control, certainly cheaper.

Bob this is very interesting information, particularly the observation from your group member. I will follow your advice and try to limit the temperature fluctuations to a minimum (I got one of the original blue cloth Zeiss covers). I don't open the windows anymore as I found out the temperature quickly rises when I open them. In fact I already covered them with tinfoil to reflect the heat

[Roldorf]

You will have to build yourself a cellar wes. That's where my kit is located it stays cool all day. When I built it I put in special breathable insulation which transports water molecules to the brickwork outside and allows the room to breath.

[MicroBob]

tinfoil

Also very helpful against electromagnetic radiation: http://www.schindluder.net/4910/schindl ... von-heute/

Occasionally I have to do with people with this problem in my job. Life has to be horrible if you see dangerous radiation everywhere - I wouldn't like to swap with them.

Bob

[Wes]

Are you a psychiatrist? My idea was to reflect IR which is part of the electromagnetic spectrum and thus limit the amount of radiant heat entering the room through the windows.

[apochronaut]

Oxidation of metal parts : avoid temperature swings. metal parts warm more slowly than the air, causing increasing atmospheric humidity to condense on metal parts. microscopes in storage are particularly vulnerable to this.

Drying of lubricants : unfortunately, air circulation increases the drying out of lubricants. This is to some degree manufacturer specific, since certain companies used lubricants that dry out worse than others. Higher storage temperatures increase volatility so lubricants dry out more quickly.

Delamination : With older cemented optical components, again, both air circulation and higher storage temperatures increase the chance of the solvent in balsam drying out to the point of causing deforming or cracking. Certain illumination systems; those with warm bulbs located right under the stage or just generally too close, and certain objective designs cause the temperature of the cement in specific elements to rise during prolonged viewing, leading to cement failure. This shows up usually as concentric swirls. Mechanical shock shouldn't be a problem with sound cement in a semi-crystalline state but once degraded to a certain point, shock could cause cracking or the separation of surfaces.

With the synthetic cements, it is a little difficult to determine the failure causes. The earlier ones, are probably sensitive to UV, so it isn't storage that is the problem but use. With certain objectives I have only ever seen cement failures in examples that have been used. N.O.S. objectives of the same age, have been 100% o.k. These also may be affected by internal heating in certain designs but some earlier cement formulas might just have been subject to degradation over time. Some seem to form internal crystals, so that isn't technically delamination. I am not sure whether that is a time or a temperature effect but I have only seen it in lenses that have been used.


Fungus : Fungus occurs on two substrates.
1) organic substances, such as fingerprints or other organic contamination. It could be on the external surfaces or on an internal surface but usually it is on an internal surface because the external surface is more often cleaned. A lens stored for a long time with the correct humidity could develop fungus on any surface. Airborne contaminants over time can be deposited inside lens systems and contrary to some camera sources spores can get inside many lens designs. Usually though, the lens left the factory with those partners in there already. Humidity, is a necessary component too. I still have a pair of W.W. II binoculars, sent to me to be cleaned. All of the internal lens and prism surfaces had a yellow film from tobacco smoke. The image looked like it was seen through a contrast filter. There was no fungus, however. Such is the power of nicotine! So, if you want to have fungus free lenses, it is best to smoke your brains out, while using them.

2)Fungus will also grow on balsam but this is more rare.

Apparently, it will also grow on coatings. Most of the earlier coatings were magnesium fluoride. There is reference in literature to "organic coatings". I don't know what these are but if they exist, probably they could serve as a fungal substrate and food supply. Fungi , are organisms that need a certain level of nutrient to prosper. I find it hard to believe that magnesium fluoride could sustain an organism. More likely, there is an organic film clinging to the coating. Perhaps the MgF2 provides a good mechanical substrate. The fungus will damage the coating, though since they produce by-products that can supposedly etch glass.

[MicroBob]

Are you a psychiatrist?

Fortunately not. I'm just one of the few people in the company who come in mind when really strange questions come up.
I honestly have absolutely no idea why they think of me in these cases!

@Phil: Thank you for covering this in a wider angle! I wouldn't dare to put optical components in the moist basement after many of mine originally came out of this surrounding and showed the signs... So I was solely focussed on the delamination topic.
Peter Höbel actually damaged a good microscope objective by means of near UV light, so this is a real problem. It is likely that when a short intensive influence of UV creates a visible defect that long time light influence creates a defect too, but less easily to detect.

BTW: A while ago I prepared the topic "Steel and material testing" for a group meeting. For this I made several polished and etched samples with arc welds, silver brazing, forged welded damascus steel , Vickers indentations etc. and had some SEM images and EDAX scans made at the university. Suddenly the operator said to me "Oops, I have burned a mark into your sample! ". And right - while focussing with an intensive beam she had left a visibl mark - IN STEEL!

Bob

[Hobbyst46]

...Peter Höbel actually damaged a good microscope objective by means of near UV light, so this is a real problem. It is likely that when a short intensive influence of UV creates a visible defect that long time light influence creates a defect too, but less easily to detect...

I have to note, that for breaking chemical bonds, wavelength is more important than intensity. UV can do what purely visible light cannot, regardless of the intensity and length of exposure. The mark on your analyzed EDAX sample was possibly caused by an X ray or powerful electron beam.

[MicroBob]

I can imagine that light that contains a small intensity in the UV range can deteriorate the glue bond when it has enough time. This cause would be difficult to detect. The delamination rate of the optics of different manufacturers might also depend on the lighting systems available in these systems. On the other hand side Zeiss West eyepieces the to delaminate too and this won't be the cause of too much UV.

[Wes]

Delamination : With older cemented optical components, again, both air circulation and higher storage temperatures increase the chance of the solvent in balsam drying out to the point of causing deforming or cracking.

Do you know if Zeiss Jena optics have a similar problem as Zeiss West?

So, if you want to have fungus free lenses, it is best to smoke your brains out, while using them.

Time to bust out the old pipe I guess

[Roldorf]

Oh man those were the days we used pencils. Signet rings cuff-links and pipes:shock:

[Wes]

According to the article I've linked below heating planapo objective to 37 C induces birefringence that may become permanent. I wonder if thats because of strain due to thermal expansion of the metal components.

The Plan Achromat objectives do not quite have the resolution of the Apochromat objectives, but they have been important for our microtubule and motor proteinassays at 37C. Heating the optics induces birefringence in the lenses, particularly the objective lenses. Eventually, heating can induce permanent birefringence, which makes the lens unsuitable for VE-DIC of fine structural detail such as individual microtubules. The Plan Achromat lenses are 1/4 the price of the PlanApochromat lenses and are, thus, less expensive to replace. We have tried to restrict our use of the expensive Plan Apochromat lenses to studies at room temperature.

https://www.sciencedirect.com/science/a ... via%3Dihub

[Hobbyst46]

According to the article I've linked below heating planapo objective to 37 C induces birefringence that may become permanent. I wonder if thats because of strain due to thermal expansion of the metal components.

The Plan Achromat objectives do not quite have the resolution of the Apochromat objectives, but they have been important for our microtubule and motor proteinassays at 37C. Heating the optics induces birefringence in the lenses, particularly the objective lenses. Eventually, heating can induce permanent birefringence, which makes the lens unsuitable for VE-DIC of fine structural detail such as individual microtubules. The Plan Achromat lenses are 1/4 the price of the PlanApochromat lenses and are, thus, less expensive to replace. We have tried to restrict our use of the expensive Plan Apochromat lenses to studies at room temperature.

https://www.sciencedirect.com/science/a ... via%3Dihub

Interesting information, yet many live cell and tissue microscopy studies are done at 37C, since this is the optimal temp for cells. Various heating methods exist: stage incubator, whole microscope climatic chamber made of plexiglass, stage hot air guns and more. The objective possibly warms up to some degree. On the other hand, DIC is ubiquitous in such studies. I believe that major objective manufacturers are aware of such issues and develop counter measures of some sort.

[Wes]

I don't know whether its an issue in general or just for video enhanced DIC which really pushes the limit so everything has to be near perfect. I know that temperature gradients in the objective are bad so there are special objective jackets that heat up the entire thing to eliminate the gradient.