I hate bubbles.

[Sure Squintsalot]

My 40 year old grad student-made thin sections, I now see, are chock full of tiny bubbles likely trapped during the epoxy mixing stage. Early (recent) attempts at plankton strews and plant stem sections fared no better. It's a problem (I think) I've solved with a de-gas chamber: I place a newly made slide inside the vacuum chamber, lock down the lid, then turn on the vacuum pump. After 15 minutes of watching the microscopic air bubbles expand their way through the Permount and out from under the cover slip, I end up with crystal clear, bubble-free slide.

But, this set-up is large, heavy, ungainly, and otherwise tied to my work bench. I'd like to have something small, lightweight, and portable enough that I could travel with it. I have some machining chops, so I could mill a single-slide chamber out plexiglass, but what about generating enough vacuum to get air bubbles out of mounting medium? Is there such a thing as a bicycle-like pump that generates vacuum? I'm also aware of the kitchen sink nozzle attachment that turn flowing water into a vacuum, too. But that requires copious water and a way to fix the adapter to a faucet. Any ideas?

[MichaelG.]

Is there such a thing as a bicycle-like pump that generates vacuum? […] Any ideas?

Yes … Find a ‘vintage’ bicycle pump [most modern ones will probably be less conveniently made] … dismantle it and reverse the leather cup-washer which forms the piston/valve.

Hey Presto !!

MichaelG.

[Chas]

A handheld vacuum pump of the sort used for brake bleeding?? :

brake bleed vacuum pump.jpg (52.05 KiB) Viewed 1790 times

[dtsh]

There are numerous hand vacuum pumps, but I would look into an electric one because the manual ones can be very ahem *tiring*'

Outside of microscopy, the two methods I know of to fight bubbles are either using vacuum to make them bigger so they raise/pop or using pressure to compress them smaller so they collapse.

[Hobbyst46]

About 3-4 years ago, a simple DIY compact vacuum chamber for slides was described on the forum. I can't remember whose idea it was (maybe Suphot ?)

A little later I constructed a device based on a 50mL Falcon tube (as chamber) and a 60mL gas-tight syringe (as a makeshift pump) and manual plastic syringe valves for the same purpose.
That too was posted here (in 2018 or 2019 maybe). Relatively simple to construct, and inexpensive. It worked, but was not great. You might try it maybe. I have to search that old post.
The problem was that obstinate bubbles need strong steady vacuum for a long duration.
A water faucet based pump, as was the laboratory standard decades ago, does not produce high vacuum, yet can be turned on for a long time (and disgustingly waste drinking water).
Indeed, an electric vacuum pump would be the best.

Edit: here it is: post "Of diatoms and air bubbles" (October 2018).
Please see responses no. 17, No. 21
Forum member mrsonchus used a pump for degassing liquid media.

[Phill Brown]

Have a look at LCD screen remover .
Separator.
They have heat and vacuum.
I put a glass slide dying/cleaning chamber upside down with the silicon pad supplied with the unit.
Had a quick look they are not as reasonably priced as they used to be.
I have model uyue 948Q which seems to still be available cheap as chips from AliExpress.

[Sure Squintsalot]

About 3-4 years ago, a simple DIY compact vacuum chamber for slides was described on the forum. I can't remember whose idea it was (maybe Suphot ?)

A little later I constructed a device based on a 50mL Falcon tube (as chamber) and a 60mL gas-tight syringe (as a makeshift pump) and manual plastic syringe valves for the same purpose.
That too was posted here (in 2018 or 2019 maybe). Relatively simple to construct, and inexpensive. It worked, but was not great. You might try it maybe. I have to search that old post.
The problem was that obstinate bubbles need strong steady vacuum for a long duration.
A water faucet based pump, as was the laboratory standard decades ago, does not produce high vacuum, yet can be turned on for a long time (and disgustingly waste drinking water).
Indeed, an electric vacuum pump would be the best.

Edit: here it is: post "Of diatoms and air bubbles" (October 2018).
Please see responses no. 17, No. 21
Forum member mrsonchus used a pump for degassing liquid media.

I didn't find "of Diatoms and air Bubbles", but I did find this thread, "Easy Chamber Slides": https://www.microbehunter.com/microscop ... ber#p34088. Seems that the hand-held vacuum pump found in brake-bleed kits may work for field applications; it seems that they can manage a pretty good vacuum. But yes, holding that vacuum over 15 minutes to properly remove stubborn or tiny bubbles may be a problem.

The LCD screen remover looks intriguing, but I wonder how low that vacuum will go. I really like the idea of heat-set AND degassing in one step. As it is, I make it 2 steps and heat my slide on a Ski-waxing iron.

[Phill Brown]

Why stick with epoxy if it's the root cause of the complaint?
It's not ideal to have no control of viscosity either.

[Hobbyst46]

Why stick with epoxy if it's the root cause of the complaint?
It's not ideal to have no control of viscosity either.

Air bubbles are a nuisance in other mounting media as well.

@Squintsalot: search keyword "30-40cps" in the MH search window (top right of the page) will lead you to the "diatoms and bubbles" thread - if it is of interest.
Somehow that "keyword" is unique in that thread !

[Sure Squintsalot]

Why stick with epoxy if it's the root cause of the complaint?
It's not ideal to have no control of viscosity either.

Air bubbles are a nuisance in other mounting media as well.

@Squintsalot: search keyword "30-40cps" in the MH search window (top right of the page) will lead you to the "diatoms and bubbles" thread - if it is of interest.
Somehow that "keyword" is unique in that thread !

Found it!
https://www.microbehunter.com/microscop ... r+bubbles

Screenshot 2023-02-08 121333.jpg (44.64 KiB) Viewed 1629 times

I have syringes and stopcocks laying around and will try this technique for degassing freshly mounted slides. I could see this being useful for (vacuum) impregnation of "loose" samples with a thin epoxy, or speeding up dehydration of hydrous materials. Are you happy with the diatom strews you're mounting with this degassing technique?

Why stick with epoxy if it's the root cause of the complaint?
It's not ideal to have no control of viscosity either.

In the case of making geological thin sections, the best, most cost-effective adhesives are clear, two-part epoxies. but I have plant sections mounted in gloss nail polish or Permount that also suffer from stubborn bubbles.

[MicroBob]

The amount of trouble with bubbles depends on what you do with the mountant, like shaking, carrying it. And it depends on the mountant itself, some hame much more problems with bubbles than others.
For plant stem sections Euparal works fine and has little problems with bubbles.
What do you do with you plancton before applying the miountant? Fixation?

[Phill Brown]

How is needing an electric vacuum pump for epoxy the most cost effective choice of mounting medium?
I have an electric vacuum pump also but never needed it for bubbles in slides.
Had a job and a half removing epoxy from the head of a microscope ditched from a university aerospace department, must be a cost cutting student thing.
Not tested epoxy for birefringence but I'd be interested to see if it's crystal clear.

[Hobbyst46]

Air bubbles are a nuisance for many mountants, worse for viscous ones.
I never used epoxy for mounting. I know quick-setting and slow-setting epoxies like Araldite; at home I use Poxypol. It is quick-setting, becomes very viscous within minutes. Even in the winter. I assume that for your slides, slow-setting epoxies are used ?

I tried the syringe-Falcon tube combination for Norland-61 mounted slides and it worked, but not so well. Yet the problem with that UV-curable cement is that it does not fill the valves of the clean diatom very well - at least those diatoms that I mounted. So other bubbles became relatively unimportant.

I very much support Bob's opinion on bubbles in the mountant: Leave the mountant motionless and quiet long enough to have bubbles float and disappear on their own.

However, if one has to warm the mountant, dissolved air will definitely lead to bubbles. Likewise, mixing epoxy components. Maybe it is possible to mix the two components very gently (neither shaken nor stirred !), to avoid bubbles.
As for ready to use mountants, like Permount, I would suggest finding the highly detailed and instructive thread by mrsonchus on the forum. He prepared great plant section plants and I remember a view of his vacuum degassing device in his lab.

[Sure Squintsalot]

How is needing an electric vacuum pump for epoxy the most cost effective choice of mounting medium?

It's cost effective if you're a graduate student needing to make dozens of thin sections, at $50 each, and can't afford high-end UV curable low-viscosity epoxies.