I hate bubbles.

Here you can discuss sample and specimen preparation issues.
Post Reply
Message
Author
Sure Squintsalot
Posts: 393
Joined: Mon May 16, 2022 3:44 pm

I hate bubbles.

#1 Post by Sure Squintsalot » Tue Feb 07, 2023 7:03 am

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.
Posts: 3976
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

Re: I hate bubbles.

#2 Post by MichaelG. » Tue Feb 07, 2023 8:38 am

Sure Squintsalot wrote:
Tue Feb 07, 2023 7:03 am
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.
Too many 'projects'

Chas
Posts: 422
Joined: Tue Jan 19, 2021 3:11 pm

Re: I hate bubbles.

#3 Post by Chas » Tue Feb 07, 2023 7:43 pm

A handheld vacuum pump of the sort used for brake bleeding?? :
brake bleed vacuum pump.jpg
brake bleed vacuum pump.jpg (52.05 KiB) Viewed 5250 times

dtsh
Posts: 977
Joined: Wed May 01, 2019 6:06 pm
Location: Wisconsin

Re: I hate bubbles.

#4 Post by dtsh » Tue Feb 07, 2023 7:49 pm

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
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: I hate bubbles.

#5 Post by Hobbyst46 » Tue Feb 07, 2023 8:45 pm

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
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: I hate bubbles.

#6 Post by Phill Brown » Tue Feb 07, 2023 11:05 pm

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
Posts: 393
Joined: Mon May 16, 2022 3:44 pm

Re: I hate bubbles.

#7 Post by Sure Squintsalot » Wed Feb 08, 2023 5:05 am

Hobbyst46 wrote:
Tue Feb 07, 2023 8:45 pm
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
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: I hate bubbles.

#8 Post by Phill Brown » Wed Feb 08, 2023 9:24 am

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
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: I hate bubbles.

#9 Post by Hobbyst46 » Wed Feb 08, 2023 3:43 pm

Phill Brown wrote:
Wed Feb 08, 2023 9:24 am
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 ! :lol:

Sure Squintsalot
Posts: 393
Joined: Mon May 16, 2022 3:44 pm

Re: I hate bubbles.

#10 Post by Sure Squintsalot » Wed Feb 08, 2023 7:28 pm

Hobbyst46 wrote:
Wed Feb 08, 2023 3:43 pm
Phill Brown wrote:
Wed Feb 08, 2023 9:24 am
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 ! :lol:
Found it!
https://www.microbehunter.com/microscop ... r+bubbles
Screenshot 2023-02-08 121333.jpg
Screenshot 2023-02-08 121333.jpg (44.64 KiB) Viewed 5089 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?
Phill Brown wrote:
Wed Feb 08, 2023 9:24 am
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
Posts: 3154
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: I hate bubbles.

#11 Post by MicroBob » Wed Feb 08, 2023 8:58 pm

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
Posts: 604
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: I hate bubbles.

#12 Post by Phill Brown » Wed Feb 08, 2023 9:03 pm

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
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: I hate bubbles.

#13 Post by Hobbyst46 » Wed Feb 08, 2023 10:35 pm

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
Posts: 393
Joined: Mon May 16, 2022 3:44 pm

Re: I hate bubbles.

#14 Post by Sure Squintsalot » Thu Feb 09, 2023 12:46 am

Phill Brown wrote:
Wed Feb 08, 2023 9:03 pm
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.

AntoniScott
Posts: 108
Joined: Tue Dec 24, 2019 3:54 pm

Re: I hate bubbles.

#15 Post by AntoniScott » Tue Apr 11, 2023 12:17 pm

Bubbles can be very aggravating and makes the final slide look like it was prepared by an amateur.
I used to be plagued with bubbles when I mounted the final specimin. It took me a while to figure out what was going on but I thought it was the dry surface of the cover slip or glass slide that contributed to the appearance of bubbles. Through experimentation, I came up with a procedure that dramatically reduced bubbles in my slides.

The final step for mounting my slides was to remove the specimin from 100% Xylene and place it on the permanent glass slide. It is important to not let the xylene on the specimin evaporate off. Mounting medium (in my case Fisher Permount) is dispensed onto the permanent slide using a glass pipette which was "pre-wetted" with xylene to reduce the surface tension, improve the flow and minimize or eliminate any bubbles. . If I see that there are any bubbles in the mounting medium, I return it to the original container and make a second attempt to withdraw mounting medium.

Sometimes it helps to "pre-wet" the pipette with xylene so to as to reduce the surface tension between the glass and the Permount. When I apply the Permount (I usually make whole mount slides of insects, or insect parts) I start from one end of the slide and dispense it over the specimin to the other end making sure that the specimin is fully covered with Permount.

The most critical step is the final step when I apply the cover slip. I place one end of the cover slip into the Permount at one end of the specimin slide and very slowly lower the cover slip down over the Permount flooded specimim. The speed at which I lower the slide over the specimin is critical and is determined by how viscous the Permount is. I pay attention to how the Permount attaches to the cover slip as it is lowered as it moves by capillary action. If I see that a bubble might get trapped, I raise the cover slip a tiny bit to allow the slow moving Permount to catch up and not create a bubble. I guess this part is as much an art as a science. You might also cosider dipping the cover slip in xylene prior to applying to the slide. The xylene will remove the surface tension of the dry cover slip and allow it to let the Permount spread without creating a bubble.

It is also possible that bubbles are introduced from the lowering of the coverslip onto the specimin because too much time was taken between applying the Permount and applying the coverslip. Unattended Permount tends to dry with a "skin" on its surface with the liquid Permount underneath.
Speeding up this procedure or wetting the coverslip with xylene will help immensely.

Hope that helps.

Antoni

Sure Squintsalot
Posts: 393
Joined: Mon May 16, 2022 3:44 pm

Re: I hate bubbles.

#16 Post by Sure Squintsalot » Wed Apr 12, 2023 6:24 pm

I use the same combination of Permount and xylene as you. I think you're onto something regarding surface tension and the cover slip. I've noticed that how I clean the cover slip has an important effect on the flow of Permount over the surface. However, I don't clean the slides, and maybe I should clean them the same way I clean the cover slips.

I should think about this more.

Post Reply