Buying expired slides - hit or miss

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Hobbyst46
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Buying expired slides - hit or miss

#1 Post by Hobbyst46 » Thu May 06, 2021 3:24 pm

I still use quality slides that expired ~30 years ago. I thought that expiration was due to the loss of sterility, since some of them had been originally sterile.
And today, I do not need sterile slides. These slides look and feel like new, and are crystal clear.

Recently I was tempted to buy quality slides that officially expired 17 years ago. To my dismay, although they are still packed in their original wrapping and box, each and every slide is covered with a white layer of crystalline dendrites, and/or mold, and/or chemical stains. So I found that the manufacturer states that expired slides might be chemically and physically damaged due to long term exposure to the environment, and cannot be revived.

Nevertheless I tried to clean them, stepwise:
- gentle rubbing under a flow of water
- boiling in a strong solution of citric acid
- rubbing with a sponge saturated with a dish soap
- same, with Chlorox
- same , with a sink-cleaning cream
- 24 hour immersion in a solution of a special detergent for glass labware

All of which removed almost all the disgusting white layer. Yet, only about 10% of the slides became acceptable; most of them remained slightly and non-uniformly foggy. very few became 100% transparent.

My verdict - buying expired slides is a dubious investment.
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apochronaut
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Re: Buying expired slides - hit or miss

#2 Post by apochronaut » Thu May 06, 2021 6:11 pm

Same with coverslips, which will fuse with a coating into nice murky glass block. If you had enough of them you could build a bathroom window.


lt is odd that some do and some don't. Possibly the result of differing glass composition.

Charles
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Re: Buying expired slides - hit or miss

#3 Post by Charles » Thu May 06, 2021 6:33 pm

This made me look at my slides.
I usually buy them in large lots, when they are sold at a great savings, and have various manufacturers...Leica, Fisher Scientific, Globe Scientific and none have expiration dates. They do have catalog and lot numbers and date manufactured, but none with expiration dates. I also have some old off brand boxes of slides, some with paper in between the slides and some stuck together and some with a film on them. Some say non-corrosive, so I imagine there may have been slides which were 'corrosive', which you maybe seeing? But the ones I have all seem to come clean with just dish soap and water. With some I need to scrub with a dish cloth, but they have all come clean after rinsing and drying.
Coverslips I clean the same way but if it takes more than a gentle cleaning, I throw them away.

Hobbyst46
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Re: Buying expired slides - hit or miss

#4 Post by Hobbyst46 » Thu May 06, 2021 7:15 pm

Charles wrote:
Thu May 06, 2021 6:33 pm
...Leica, Fisher Scientific, Globe Scientific and none have expiration dates. They do have catalog and lot numbers and date manufactured, but none with expiration dates.
The ones I bought are wrapped with cellophane in 50-piece cardboard boxes; there are lot numbers and an hourglass symbol for 2006-11. Which I take as expire in November, 2006. They are titled as pre-cleaned/ready-to-use, so not coated for cell culture or other specific research.

After the cleaning attempts, and drying with a piece of KimWipe, haziness still shows up when I hold them against a bright lamp; also, holding them at an angle, so that they reflect light like mirrors, shows a strange pattern reflective surface, as if an extremely thin non-uniform network has been attached onto the initially perfect surface of the slide.

The 30+ years old slide that I uses and are still OK had been supplied on that time by PGC Scientific, before it merged with Fisher, and were made in USA I think.

Edit: Out of curiosity searched eBay and found this item, with an expiry date printed on the box
https://www.ebay.com/itm/312520996547?h ... SwqrVcgpxN
Last edited by Hobbyst46 on Thu May 06, 2021 7:53 pm, edited 1 time in total.
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jmp
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Re: Buying expired slides - hit or miss

#5 Post by jmp » Thu May 06, 2021 7:41 pm

I had some very old but new slides that were also covered with a layer of some white residue, stuck together and cloudy, similar to what Hobbyst46 described. Tried to clean them in a similar way, and the results were similar. What made a difference though was polishing them with toothpaste; a larger fraction of slides ended up being transparent and usable for casual use. They still had defects after 'polishing', like scratches and stains but were usable for brightfield; definitely not usable for darkfield though.

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75RR
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Re: Buying expired slides - hit or miss

#6 Post by 75RR » Thu May 06, 2021 8:31 pm

.
Had not come across an expiration date on slides or cover slips - so news to me. Thanks for the tip.
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MicroBob
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Re: Buying expired slides - hit or miss

#7 Post by MicroBob » Thu May 06, 2021 9:01 pm

Hi together,
this is a really interesting topic. Even some really experienced microscopists are not aware of this problem and it is not discussed much. I don't like to throw things away (asky my wife) and tend to buy lifelong supplies of everything and use them up over time. I also like to make permanent slides and while I try to stay away from too pedantic aims I like them to be quite okay. So I was annoyed by this problem and looked closer into what is happening:
Slides are made of soda lime glass which is hygroscopic. This doesn't seem to be a problem when the glass is separated from others (like a window pane from similar glass type) but it starts to become a problem when the slides are together in a pack. For this reason they are sometimes sold in aluminium bags of 1000 slides or so. Cover slips are usually made from borosilicate glass which has a better hydrolysis resistance than soda-lime glass. And really, while I have cover slips that have deteriorated this is fairly rare.

So what can be done? It probably would help to store the slides very dry or in a fluid that keeps water concentration low like ethanol.
And there are borosilicate-glass slides: https://www.laborshop24.de/duran-standa ... tueck.html

Bob

Hobbyst46
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Re: Buying expired slides - hit or miss

#8 Post by Hobbyst46 » Thu May 06, 2021 9:10 pm

Thanks for the link, Bob.
Indeed, the deteriorated slides I described were compactly packed without any separation between two neighboring slides.
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MicroBob
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Re: Buying expired slides - hit or miss

#9 Post by MicroBob » Fri May 07, 2021 7:18 am

Hi Doron,
what I find interesting is that this process can take place in varying speeds. I had fairly recent slide packs go bad while some decades old are not perfect but quite okay. And I would expect the slides to deteriorate separated in boxes too. From household glassware I know this too, glasses often become opaque after some years. Very interesting from my point of view.

Bob

Leitzcycler
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Re: Buying expired slides - hit or miss

#10 Post by Leitzcycler » Fri May 07, 2021 8:06 am

I am also familiar with this. It is not even a matter of decades but I have a package bought a couple of years ago which already have some fuzzy dots on the surface of slides. My solution: I just wash them with Fairy under hot water with a brush. Then I wipe them with paper towel. Though it is no 100% clean, it is quite satisfactory for my applications. I think for me there is no need to be a perfectionist in this as there is certainly more dust in my microscopy optics.

Anyway I am very interested to hear about the phenomenon. Storing the slides in a dessiccator would be a solution. However, I have never seen or heard any precautions in any lab.

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Re: Buying expired slides - hit or miss

#11 Post by MicroBob » Fri May 07, 2021 8:36 am

I think this problem is often overlooked and some people just don' t experience it. The hazy surface comes from a degradation of the slide surface, like small pits. When using a mountant that has a refractive index near that of glass the might be less visible. In thick mounts they might be safely out of focus. But for very thin mounts, mountants with high or low refractive index and darkfield use they can be a problem.

Hobbyst46
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Re: Buying expired slides - hit or miss

#12 Post by Hobbyst46 » Fri May 07, 2021 10:30 am

MicroBob wrote:
Fri May 07, 2021 8:36 am
I think this problem is often overlooked and some people just don' t experience it. The hazy surface comes from a degradation of the slide surface, like small pits. When using a mountant that has a refractive index near that of glass the might be less visible. In thick mounts they might be safely out of focus. But for very thin mounts, mountants with high or low refractive index and darkfield use they can be a problem.
My concern is mainly the effect on illumination. Non-uniform illumination due to cloudiness of regions on the slide will show in images; intuitively, darkfield, phase and oblique (and DIC ?) will be affected. My intuitive - perhaps over-cautious - approach is to discard any slide that is not 95% free from haziness and scratches.
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Leitzcycler
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Re: Buying expired slides - hit or miss

#13 Post by Leitzcycler » Fri May 07, 2021 11:34 am

My very limited experience arises from hanging around in labs preparing either histological or microbiological samples. I think very few people there even knew what oblique or DIC is. Anyway having 100% clean slides is of course bright and beautiful. However, I am pretty sure someone did win the Nobel price using foggy slides :)

So, is this the prevalent hypothesis: hygroscopic slides absorb water which enable fungus growth. Fungus then eats the glass and/or excrete corrosive metabolites which degrade the slides. When cleaning, you can remove the fungus but not the marks of corrosion?

Leitzcycler
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Re: Buying expired slides - hit or miss

#14 Post by Leitzcycler » Fri May 07, 2021 1:11 pm

Prize,

sorry for my poor English :oops:

Hobbyst46
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Re: Buying expired slides - hit or miss

#15 Post by Hobbyst46 » Fri May 07, 2021 1:30 pm

Leitzcycler wrote:
Fri May 07, 2021 11:34 am
So, is this the prevalent hypothesis: hygroscopic slides absorb water which enable fungus growth. Fungus then eats the glass and/or excrete corrosive metabolites which degrade the slides. When cleaning, you can remove the fungus but not the marks of corrosion?
From what I have read, it is rather a chemical process: glass is not so chemically stable, it slowly interacts with moisture and carbon dioxide, and when the surface composition changes, transparency suffers. I am not sure that fungus is really there.

I found a way to demonstrate the effect. The side-illuminated slide holder serves for diatom selection, and is shown here lying beneath the mechanical finger on the stereoscope stage. A round ND filter is placed on it and serves as a mirror. The suspected slides are placed on top, one by one, and photographed. Dust is removed from each part, but obviously some dust remains. Three expired slides are shown: A - as received, B and C - after cleaning. In comparison to a brand new slide from a different brand. The majority of the cleaned slides are similar to B, but even C is not as good as new.

An interesting, though not free, lesson !
Attachments
1) Side-illuminated slide holder, here with an ND filter - round mirror - under the slide..  .jpg
1) Side-illuminated slide holder, here with an ND filter - round mirror - under the slide.. .jpg (91.85 KiB) Viewed 480 times
2) No slide. The bright north-west region is a reflection of the mechanical finger.jpg
2) No slide. The bright north-west region is a reflection of the mechanical finger.jpg (33.63 KiB) Viewed 482 times
3) With a brand-new slide, the one shown in photo 1.jpg
3) With a brand-new slide, the one shown in photo 1.jpg (34.76 KiB) Viewed 482 times
4) Expired slide A, out of the original packing.jpg
4) Expired slide A, out of the original packing.jpg (114.44 KiB) Viewed 482 times
5) Cleaned expired slide B.jpg
5) Cleaned expired slide B.jpg (47.68 KiB) Viewed 482 times
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Hobbyst46
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Re: Buying expired slides - hit or miss

#16 Post by Hobbyst46 » Fri May 07, 2021 1:35 pm

(continued)
Attachments
6) Cleaned expired slide C, considered acceptable.jpg
6) Cleaned expired slide C, considered acceptable.jpg (24.65 KiB) Viewed 480 times
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MicroBob
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Re: Buying expired slides - hit or miss

#17 Post by MicroBob » Fri May 07, 2021 6:03 pm

Hi Doron,
your photos 4 and 5 show patterns that could go as fungus or bacterias. And some glass fungi emit acidous substances that can etch glas, typically the fungi that spread like a bizarre spider web. So to me fungus infction would be a possible explanation to look into. The damages I had so far looked more evenly spread, like a haze that doesn't fully clean up when the slides are cleaned. But so far I haven't put them under a microscope to tell the truth. Sometimes the do feel slightly wet, like eye glasses after a walk along the north sea coast in stormy wheather.

Bob

Hobbyst46
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Re: Buying expired slides - hit or miss

#18 Post by Hobbyst46 » Sat May 08, 2021 8:44 am

MicroBob wrote:
Fri May 07, 2021 6:03 pm
Hi Doron,
your photos 4 and 5 show patterns that could go as fungus or bacterias. And some glass fungi emit acidous substances that can etch glas, typically the fungi that spread like a bizarre spider web. So to me fungus infction would be a possible explanation to look into. The damages I had so far looked more evenly spread, like a haze that doesn't fully clean up when the slides are cleaned. But so far I haven't put them under a microscope to tell the truth. Sometimes the do feel slightly wet, like eye glasses after a walk along the north sea coast in stormy wheather.

Bob
Here are compound microscope views under 10X objective, of slide A (as received).
Attachments
IMG_5658.JPG
IMG_5658.JPG (58.68 KiB) Viewed 421 times
IMG_5657.JPG
IMG_5657.JPG (65.75 KiB) Viewed 421 times
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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