Of diatoms and air bubbles

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Hobbyst46
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Of diatoms and air bubbles

#1 Post by Hobbyst46 » Sun Oct 21, 2018 7:04 pm

Here is my experience with (hopefully) permanent strew slides of diatom mounted in the UV-curable adhesive NOA61. I brought it to room temperature prior to use. Dried a drop of an old batch of gently cleaned diatoms on coverslips. Then, incinerated the coverslips on a metal plate for 12min, to burn out some organic residues. The heating created some black spots that show in the photos. Then mounting. Only the smallest drop should be taken for a 18x18 or a 22x22 mm coverslip. And 30min curing (arbitrary duration).
In general, in about 20 slides, air bubbles appeared occasionally but were usually a minor interference. However, the large diatoms, like rounded-corner rectangles with small circular tips apparently gave off bubbles, shown as dark-rim circles. So, since the mountant is viscous, air does not easily escape from within these specific frustules. Or, perhaps, random air bubbles attach themselves to the nice "cradle" valves - which I do not believe...
The "bubbled diatom" length is 67um.

NOA61 is very easy to use and does not involve solvents. I do not know if heating will prevent hese bubbles or not, but I believe that the bulk of adhesive should be kept cold to prolong its shelf life.
Its RI is quite similar to that of PS-CBO (1.56-1.6). The latter mountant does not produce unsightly bubbles, but, on the other hand, does not solidify and only keeps well up to about 6 months - and is difficult to seal. NOA61 is hence advantageous, and I should build a degassing chamber - or switch to resins instead. With a resin, some solvent is usually added (according to protocols) to drive off the air from the frustules.
note: for curing - I inverted the slides, top down, on top of the UV lamp, as suggested by rnabhoz.
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25X0.45 phase contrast.JPG
25X0.45 phase contrast.JPG (163.97 KiB) Viewed 6278 times
40X0.75 phase contrast.JPG
40X0.75 phase contrast.JPG (162.08 KiB) Viewed 6278 times
40X0.75 P.C. 2.JPG
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40X0.75 P.C. 4.JPG
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MichaelBrock
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Re: Of diatoms and air bubbles

#2 Post by MichaelBrock » Sun Oct 21, 2018 9:13 pm

My NOA61 slides also have these air bubbles in many of the larger diatoms. I have seen recommendations with other mountants to first wet the slide with a drop of solvent to displace the air bubbles. Not an option here. As you suggest maybe heating to make it less viscous?

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Re: Of diatoms and air bubbles

#3 Post by rnabholz » Mon Oct 22, 2018 12:30 am

Hi Hobby.

Interesting post, thanks for sharing your experience.

As i look at the images, i am struck by the lack of details in the frustules. It seem like you should be seeing more.

Perhaps you are, and if so, disregard my comments. For comparison, here is an afocal shot thru a 10x objective of a pleurax mounted strew.
Diatom View 7.jpg
Diatom View 7.jpg (155.88 KiB) Viewed 6250 times
How are the views at higher magnifications?

Again, thanks for sharing your efforts.

Rod

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Re: Of diatoms and air bubbles

#4 Post by zzffnn » Mon Oct 22, 2018 3:22 am

Rod,

Hobbyst46 was using phase contrast (for initial rough screening?), which won't produce the same resolution as brightfield or oblique (effective NA of phase contrast is typically half of objective NA - in other words, you will only get about NA 0.38 from a phase NA 0.75 objective).

His Canon M10 seems to have electronic first curtain, so I assume he used it (so shutter vibration did not reduce resolution).

We also have to factor in mountant's effect on resolution. NOA61's RI value (1.56-1.6?) is not as high as Pleurax (RI=1.73), so that may also play a role.

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Re: Of diatoms and air bubbles

#5 Post by MicroBob » Mon Oct 22, 2018 10:19 am

Hi Doron,
I think the slides would profit from less diatom material per area and all material in one plane.
Would it be possible to spread a thin layer of NOA61, apply diatom material, UV-cure (at least to some extent) and then apply more NOA61 on the permanently located diatoms?

Diatoms have an r.i. of up to 1,53, more typical around 1,45 or so. For good visibilty a r.i. difference of 0,1 is suggested. So for most diatoms you should get an acceptable image in bright field.

Bob

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Re: Of diatoms and air bubbles

#6 Post by rnabholz » Mon Oct 22, 2018 1:19 pm

zzffnn wrote:Rod,

Hobbyst46 was using phase contrast (for initial rough screening?), which won't produce the same resolution as brightfield or oblique (effective NA of phase contrast is typically half of objective NA - in other words, you will only get about NA 0.38 from a phase NA 0.75 objective).

His Canon M10 seems to have electronic first curtain, so I assume he used it (so shutter vibration did not reduce resolution).

We also have to factor in mountant's effect on resolution. NOA61's RI value (1.56-1.6?) is not as high as Pleurax (RI=1.73), so that may also play a role.
Thanks zz.

I think you know that I have some experience with phase contrast, and took that into consideration when making the comment. I would still offer that a 70 micron caloneis at 400x should be offering up more detail than we are seeing here regardless of the lighting technique. There has to be something else going on.

As you offered, I do think it may involve the R. I.. of the mountant.

The other thing i am wondering about is how it cures. It seems that the diatoms settled a widely different levels. Hobby indicated that he used the inverted cure technique, which using Pluerax, facilitates the settling of the diatoms on the slip. Is it possible that this mountant is thicker and/or cures differently in a way that prevents any movement during the curing?

Thanks again to Hobby for sharing his results, very interesting.

Rod

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Re: Of diatoms and air bubbles

#7 Post by Hobbyst46 » Mon Oct 22, 2018 2:37 pm

Thanks all folks for your kind responses! I am still working on it but would like to comment on as far as I know.
MichaelBrock wrote:My NOA61 slides also have these air bubbles in many of the larger diatoms. I have seen recommendations with other mountants to first wet the slide with a drop of solvent to displace the air bubbles. Not an option here. As you suggest maybe heating to make it less viscous?
Perhaps adding a solvent in this case is an option - it will not be a solvent actually, just a liquid of high RI to penetrate the frustules, displace air and still not interfere with the curing and the quality of the cured product. I am pondering this option but so far reject it.
Heating sounds an option: I found the viscosity data of NOA61 in the mfg site. It goes down from 500cps to 200cps (cps is a viscosity unit) with temperature increasing from 19C to 31.3C, BUT non-linearly. So I fitted an exponential curve to the numbers and cheekily extrapolated to estimate that the viscosity will be 80cps at 40C, 30-40cps at 45C, 15-20cps at 47C, and 0-1cps at 50C :lol: :lol: . The mfg says it is usable up to 60C. But, the possible catches are that the curing rate becomes too fast, uneven layer, lumps, perhaps a lower RI - who knows? So, I would give it a try: put a tiny drop of the stuff (at room temperature) on the slide, invert the slide onto the diatom-coated coverslip, place the sandwich, inverted, in a small oven at 45C (avoid dripping of the liquid outwards) for, say, 5-10min, and cure. Hopefully it will work.
zzffnn wrote: Hobbyst46 was using phase contrast (for initial rough screening?), which won't produce the same resolution as brightfield or oblique (effective NA of phase contrast is typically half of objective NA - in other words, you will only get about NA 0.38 from a phase NA 0.75 objective).

His Canon M10 seems to have electronic first curtain, so I assume he used it (so shutter vibration did not reduce resolution).

We also have to factor in mountant's effect on resolution. NOA61's RI value (1.56-1.6?) is not as high as Pleurax (RI=1.73), so that may also play a role.
rnabholz wrote:As i look at the images, i am struck by the lack of details in the frustules. It seem like you should be seeing more.
Yes folks, the resolution is less than decent. I really was doing an initial rough screening, in phase contrast. The optical setup is stable, EFC is being used, so the lack of details might originate from the lack of contrast, due to the (relatively low) RI of the mountant. I will try brightfield for better contrast. My aim, though, was to demonstrate the specific air bubble issue, but I should definitely try to improve image quality.
MicroBob wrote:I think the slides would profit from less diatom material per area and all material in one plane.
Agreed. My diatoms tend to clump together, especially after long-term storage in a test tube. I tried to break them apart with ammonium chloride, but it did not work.
MicroBob wrote:Would it be possible to spread a thin layer of NOA61, apply diatom material, UV-cure (at least to some extent) and then apply more NOA61 on the permanently located diatoms?
Initially, the diatoms are layered on the coverlip, and I HOPE that the adhesive does not detach them. I hope that the adhesive just forms a thin layer, keeping the diatoms as close to the coverslip as possible. I do not think I can make such a thin layer of mountant that will not interfere. Bob, perhaps you could explain the idea in more detail? but please note, that the mountant is fairly viscous.
MicroBob wrote:Diatoms have an r.i. of up to 1,53, more typical around 1,45 or so. For good visibilty a r.i. difference of 0,1 is suggested. So for most diatoms you should get an acceptable image in bright field.
This is what I had hoped.
rnabholz wrote:The other thing i am wondering about is how it cures. It seems that the diatoms settled a widely different levels. Hobby indicated that he used the inverted cure technique, which using Pluerax, facilitates the settling of the diatoms on the slip. Is it possible that this mountant is thicker and/or cures differently in a way that prevents any movement during the curing?
Yes. My starting point is not good - too dense a strew, they are. So not all diatoms are at the same plane. Adding the NOA61 does not change the distribution (I think). The application of Pleurax is different: I think that heating the Pleurax (and the added IPA of course) until boiling of the solvent, bubbles etc may move the diatoms, and they settle just as you describe. Again, these effects are related to the specific properties of the mountant.

One more comment about the adhesive I used. There is a wide range of NOA adhesives, which vary in RI, viscosity, hardness after curing, availability and price. All these features count. To me, NOA61 seemed to be better than others. For example, NOA170 has an RI of 1.7, but it is highly viscous, requires nitrogen for curing and remains a tacky/flexible layer. So...
What I take home from these experiments (I am at home of course :lol: ) is the specific diatom-created air bubble.

Important: Thanks, Rod, for identification of the bubble-loaded diatom, Caloneis!
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Re: Of diatoms and air bubbles

#8 Post by MicroBob » Mon Oct 22, 2018 6:19 pm

When making arranged diatom slides on regularly spreads thin layers of e.g. shellac and skin fat on the cover slip to first deposit the diatoms and then glue them in place. With NOA61 you might be able to smear it onto the cover slip with a piece of plastic or so. One additional advatage would be that the diatoms would be penetrated from all sides.

One more idea (I have been working with concrete in the past weeks): Vibration might help the NOA61 to enter the frustules. An electric toothbrush or a piezo beeper might be worth a try.

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Re: Of diatoms and air bubbles

#9 Post by Hobbyst46 » Mon Oct 22, 2018 9:15 pm

MicroBob wrote:When making arranged diatom slides on regularly spreads thin layers of e.g. shellac and skin fat on the cover slip to first deposit the diatoms and then glue them in place. With NOA61 you might be able to smear it onto the cover slip with a piece of plastic or so. One additional advatage would be that the diatoms would be penetrated from all sides.

One more idea (I have been working with concrete in the past weeks): Vibration might help the NOA61 to enter the frustules. An electric toothbrush or a piezo beeper might be worth a try.
Thanks Bob. So there are four options already: Warming to 45-50C; Degassing; A top layer glue; Vibrations. Will see!
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Re: Of diatoms and air bubbles

#10 Post by zzffnn » Tue Oct 23, 2018 12:47 am

Rod,

My apologies. I did not mean to call you out. I meant to say that Hobbyst46 should not expect his phase-NOA61 photos to be as dot-resolving as your brightfield-Pleurax photo, as many factors are different.

Apparently, he already knew that and had a slightly different purpose (which was initial proof of concept) in mind.

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Re: Of diatoms and air bubbles

#11 Post by rnabholz » Tue Oct 23, 2018 2:01 am

zzffnn wrote:Rod,

My apologies. I did not mean to call you out. I meant to say that Hobbyst46 should not expect his phase-NOA61 photos to be as dot-resolving as your brightfield-Pleurax photo, as many factors are different.

Apparently, he already knew that and had a slightly different purpose (which was initial proof of concept) in mind.
No worries, I didn't take it that way, sorry if it sounded like I did.

I thought even with phase, it should be showing more, and I suspected the RI of the mountant was the issue.

Hobby: I think it's Caloneis Amphisbaena. Here is one about the same size that i shot, its a cool form.
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Caloneis amphisbaena 1395.JPG
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Re: Of diatoms and air bubbles

#12 Post by Hobbyst46 » Tue Oct 23, 2018 1:00 pm

zzffnn wrote:...I meant to say that Hobbyst46 should not expect his phase-NOA61 photos to be as dot-resolving as your brightfield-Pleurax photo, as many factors are different. Apparently, he already knew that and had a slightly different purpose (which was initial proof of concept) in mind.
yes, indeed.
rnabholz wrote:I thought even with phase, it should be showing more, and I suspected the RI of the mountant was the issue.
Agreed.
Having done some more microscopy with the NOA61 slides, I found that all brightfield images were of poor contrast, at least relative to Rod's brightfield 10x "diatom view 7" photo above, and are not worth showing.
I tried some high-mag views of the diatoms, mounted in NOA61, and for comparison, in the non-permanent mountant PS-CBO. All with 100X1.3 Ph3 Planapo (immersion - objective oiled only, laziness...), under phase contrast and oblique.

There are almost no air bubbles here, with the smaller diatoms than caloneis.
I think that the RI's of the mountants yield similar visibilities. I also think that the resolution is OK; contrast is low. The visibility (if that is the correct term) is sensitive to the RI difference (more than linear dependence) so indeed, Pleaurax will perform better. I still hope to use it one day; and replace the camera zoom lens with a prime lens as well.
Attachments
32um(large cocconeis {ellipse}); phase, NOA61.JPG
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32um(large cocconeis {ellipse}); oblique, NOA61.JPG
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120um; phase, NOA61.JPG
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120um; oblique, NOA61.JPG
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Re: Of diatoms and air bubbles

#13 Post by Hobbyst46 » Tue Oct 23, 2018 1:02 pm

(continued)
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50um; oblique, PS-CBO.JPG
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20um; phase, PS-CBO.JPG
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20um; oblique, PS-CBO.JPG
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Re: Of diatoms and air bubbles

#14 Post by Hobbyst46 » Tue Oct 23, 2018 1:03 pm

(continued)
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Re: Of diatoms and air bubbles

#15 Post by MicroBob » Tue Oct 23, 2018 5:24 pm

Hi Doron,
that looks already quite as expected. Rod has cheated: He has raised the contrast in his image so it look crisper.
If you apply the same mount of image editing on your pictures they are not far away. Apart from that pictures with the 10:1 always have better contrast than with stronger magnifications.
The perfect mountant depends on the massiveness of the structures. For small diatoms a higher r.i is more important than for bigger, stronger diatoms.
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Re: Of diatoms and air bubbles

#16 Post by Hobbyst46 » Tue Oct 23, 2018 8:50 pm

Thanks Bob!

The images I posted are really quite raw. Single images, resized and slightly cropped to fit the upload limitations.
I believe, though, that also Rod's diatom view 7 is not post processed...

Incidentally, I just developed the simplest vacuum device, based on two plastic syringes in parallel, for degassing. it is still experimental...
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Re: Of diatoms and air bubbles

#17 Post by mrsonchus » Tue Oct 23, 2018 11:38 pm

Hi, concerning a simple vacuum device/chamber.
I use a hand vacuum-pump designed for use with car brake systems, see my post HERE

It may be just the job for a small chamber, although in the post I use it to degass plant tissue during processing for slide making.

John.
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Re: Of diatoms and air bubbles

#18 Post by rnabholz » Wed Oct 24, 2018 12:19 am

Hobby,

These are showing nice detail and some very nice forms as well. Keep experimenting and sharing the results.

Regarding my images, it has been a while, but the strew pic was a quick resize and post image from my cell phone just to demonstrate the view of one of my first strews, I don't remember if I adjusted levels or curves, but I doubt I did seeing the purpose of posting it.

Otherwise, I embrace the Cheat.... ;^). I readily admit to processing my images, as ham handed as I am at it.

My interest is to present the best images that I can. Some of that comes from the processing and mounting, some of that comes from the capture, and some certainly from post processing. I have yet to see an image captured with today's digital cameras that cannot benefit from a tweak of levels or curves, and some sharpening.

I will retire from the thread now, having caused enough of a distraction, but I will be watching for your updates.

Rod

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Re: Of diatoms and air bubbles

#19 Post by MicroBob » Wed Oct 24, 2018 8:29 pm

I have a similar vaccuum pump as John, bought for the same purpose.
For microscopy I use an adapter like shown below. It's a PVC frame with acrylic glass on one side and a rubber seal on the other. It fits over one complete slide.
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Re: Of diatoms and air bubbles

#20 Post by Hobbyst46 » Wed Oct 24, 2018 8:55 pm

mrsonchus wrote:Hi, concerning a simple vacuum device/chamber.
I use a hand vacuum-pump designed for use with car brake systems, see my post HERE
It may be just the job for a small chamber, although in the post I use it to degass plant tissue during processing for slide making.
John.
MicroBob wrote:I have a similar vaccuum pump as John, bought for the same purpose.
For microscopy I use an adapter like shown below. It's a PVC frame with acrylic glass on one side and a rubber seal on the other. It fits over one complete slide.
Thanks John B and Bob - your setups have been inscribed into my memory and inspired me since the day they were posted, many months ago.

But I could not make such. So instead, I found two 50-60ml disposable plastic syringes. One of them ("piston") has a rubber-top plunger, so it is fairly gas-tight. The other ("chamber") is relatively short and thick - inner diameter 27-28mm and length about 90mm, such that a slide will fit inside; there is no plunger. I can close it hermetically with a rubber stopper. The two syringes are connected to each other head-to-head through their luer tips, using a full 3-way plastic luer stopcock. All components are commercial - nothing to fabricate.

I plan to prepare the slide, grip its edge with a small paperclip, exactly as shown by Rod (rnabholz) and place it in the chamber. The paperclip keeps the slide close to the cylindrical chamber axis and away from the wall. Close the chamber with the rubber stopper and press on it to seal. Push the plunger to expel all air from the piston, using the stopcock to vent. Turn the stopcock to block room air and allow air passage only between the syringes. Withdraw the plunger to suck air from the chamber. Turn the stopcock to block the chamber and allow venting the piston. Push the plunger to expel all air from the piston - so starts cycle no 2 of the evacuation process. Like using a hand or foot pump to inject compressed air into a car tire, but with a fully manual valve/air vent. After 3-4 cycles I turn the stopcock to block the chamber, and wait.
A preliminary experiment with a slide of nail polish, without sample. I shook the nail polish bottle vigorously to create plenty of bubbles, then made a slide. Applied vacuum - seemed to help somewhat. Now for the real thing... diatoms in NOA61... (will be cont'd).
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Re: Of diatoms and air bubbles

#21 Post by Hobbyst46 » Sat Oct 27, 2018 7:19 pm

Some more data about fighting air bubbles within mountant:
I assembled the static vacuum device, described in the above text. The stopcock enables blocking ("off" handle) of each of the three ports. Note that the syringes need not be identical - one of them has a wider bore, to accept a loosely placed slide.
I prepared three diatom strew slides as follows:
1. Dry a drop of suspension onto 22x22mm coverslip.
2. Incinerate the coverslip on a steel plate for about 12 min on a small oven gas flame, to burn out residues without deforming diatoms.
3. Cool the plate to room temperature (25C).
3. Place a small drop of NOA61 (diameter, 5-6mm) on a slide, invert the slide onto the coverslip, and:

for slide A - turn on the flame under the plate for 10-15 seconds, turn off the flame, and immediately monitor the plate temperature. When it is about
50C, place the slide on the plate. The adhesive spreads quickly. Wait another minute, then transfer to UV curing.

for slide B - repeat procedure A, but prior to curing, place in the vacuum chamber. Apply vacuum by three rapidly chained air withdrawals, blocking the
chamber when the plunger is pressed inside (in between withdrawals), then leave under vacuum for 10 minutes, vent to ambient air and transfer to UV
curing.

for slide C - vacuum only, then UV curing.

It might have been better to cure under vacuum, however the syringe wall is not transparent to UV.
The results are somewhat promising, in that vacuum (slides B, C) appears to prevent diatom-bound bubbles to large extent. However, in the mountant layer itself, between diatoms quite many bubbles appeared. Slide A was not better than my previous slides with NOA61.
These are not definitive results as yet, I think I will try to repeat the vacuum step with NOA61.

Incidentally:
mrsonchus wrote:...
MicroBob wrote:...
Bob, John B., for how long do you leave the slide under continuous suction by the pump ?
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Re: Of diatoms and air bubbles

#22 Post by mrsonchus » Sat Oct 27, 2018 10:32 pm

Hi, I apply the vacuum for about 5 minutes then slowly release - this allows space formerly occupied by air to be 'refilled' by the liquid in question, usually in the case of my tissue processing this will be fixative or dehydrant (alcohol).
This is repeated several times - complete infiltration is able to be judged when all tissue sinks to the bottom of it's container, rather than being floated by any internal air.
This process is used specifically for air contained within tissue (or in your case frustules) - the prevention of air-bubbles in mountant however, assuming a degassed or gas-free mountant is used, is hugely dependant upon the surface-condition of the coverslip used....

I use the term surface-condition rather than cleanliness deliberately, as cleanliness is an absolute requirement that I presume you always adhere to. However, after a couple of years struggling with the phenomenon of bubbles in mountant with perfectly clean slides and coverslips I finally discovered the by-far most influential factor to be the coverslip's surface-condition. Pitting or degradation of the surface of the coverslip is the culprit.
To cut a long story short, once I finally found a source of perfect coverslips the problem was for my work reduced by about 95% at least.....

The prevention of an ideal flow of mountant during mounting by such surface-imperfections causes absolute chaos and results in a significant level of failure due to the appearance of air bubbles which it turns out are perhaps better described as 'missed-bits' that the mountant has failed to flow into during mounting.....

My experience of course is in the context of botanical tissue processing and mounting rather than diatom frustules - although I'd be very surprised if the above was not valid for those also.

John B.
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Re: Of diatoms and air bubbles

#23 Post by Hobbyst46 » Sun Oct 28, 2018 7:39 am

Thanks John B for the detailed answer. I will try repeated vacuum.
The effects of glass imperfections you mentioned lead me to to think about the very high frustule density on my recent slides. Possibly, the roughness of the diatom layer, with many small "holes" and cavities between diatoms and under diatom clusters, may have behaved as nucleation points for bubbles. I will try and dilute them further.
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Re: Of diatoms and air bubbles

#24 Post by MicroBob » Sun Oct 28, 2018 8:45 am

I haven't tried this yet, but it may be possible to watch the effect of the vaccuum on the bubbles under the stereo microscope to find the best timing and number of cycles. I'm about to prepare a radiolaria mounting course and have to do some experiments to find the most straight forward technique, maybe I can look into this.

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Re: Of diatoms and air bubbles

#25 Post by MichaelG. » Sun Oct 28, 2018 8:55 am

MicroBob wrote:... I'm about to prepare a radiolaria mounting course ...
That's interesting: Please tell me more [either here, or by 'private message']

Thanks
MichaelG.
Too many 'projects'

billbillt
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Re: Of diatoms and air bubbles

#26 Post by billbillt » Sun Oct 28, 2018 11:12 pm

I also would like to hear more about it...

BillT

Hobbyst46
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Re: Of diatoms and air bubbles

#27 Post by Hobbyst46 » Mon Oct 29, 2018 5:45 pm

Hobbyst46 wrote:...I assembled the static vacuum device, described in the above text. The stopcock enables blocking ("off" handle) of each of the three ports. Note that the syringes need not be identical - one of them has a wider bore, to accept a loosely placed slide.
In fact, two slides, held back to back (coverslips pointing outward) by means of the paper clip, can be degassed simultaneously. Surprisingly, the chamber in the DIY apparatus proved to be well-sealed. When evacuated, the tip blocked by the stopcock, and left alone, air leaked very slowly into the chamber, so vacuum inside withheld for half an hour, at least.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Re: Of diatoms and air bubbles

#28 Post by MicroBob » Thu Nov 01, 2018 4:07 pm

Hi Doron,
by accident I found this thread in german mikroskopie-forum:
https://www.mikroskopie-forum.de/index. ... 3#msg32523

The wood dowel might be useful for you when your vaccuum lasts for so long.

Bob

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mrsonchus
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Re: Of diatoms and air bubbles

#29 Post by mrsonchus » Thu Nov 01, 2018 4:56 pm

Hi again, yes, the syringe method was my first method! I used a combination of jars, pierced rubber-bungs, fish-tank airline and fish-tank airline-valves. The valves can not only be combined but of course used to control and maintain vacuum to several 'vacuum jars' at once.
The syringe may be removed - the valves of course will maintain the vacuum.
See below an image of my setup from then.
Oh yes, here's a link to my original post when making this system..
ws_vacuum_fixing.jpg
ws_vacuum_fixing.jpg (331.85 KiB) Viewed 5802 times
This simple system has great flexibility and costs very little indeed to make....

John :)
John B

Hobbyst46
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Re: Of diatoms and air bubbles

#30 Post by Hobbyst46 » Thu Nov 01, 2018 7:09 pm

MicroBob wrote:Hi Doron,
by accident I found this thread in german mikroskopie-forum:
https://www.mikroskopie-forum.de/index. ... 3#msg32523

The wood dowel might be useful for you when your vaccuum lasts for so long.

Bob
Hi Bob,
Thanks for the idea and link! in the response to the user of the vacuum pump in that link, a 3-way stopcock is mentioned. This is essentially what I fitted, as shown in the drawing above. With the stopcock, the evacuated chamber can be blocked, cut-off from the room air, by turning the handle towards the chamber. Since it is a full 3-way stopcock, in this very position, the piston syringe is vented - open to the room air. Hence, the plunger is stable as it stays, and is not pulled inside by the vacuum - and accordingly, a dowel is not required.
I improved my vacuum apparatus a little, by fixing the assembled apparatus on top of a plywood flat block. The width of the block is much larger than the diameter of the piston or the chamber. That leaves a rim on each side of the fixed apparatus. I clamp the block to the edge of my bench. Then the apparatus is practically anchored to the bench. I can then withdraw the plunger and hold it against the the pulling action of the vacuum with one hand; and rotate the stopcock with the other hand, to block the chamber. Quite convenient.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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