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What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 7:46 am
by Wes
I noticed that
this method mentions the use of #1 thickness glass coverslips. I was always under the impression that high precision #1.5 coverslips were best suited for this purpose.
Anyone care to enlighten me on the issue? I have noticed that slides from different diatomists require adjustment of the coverslip correction collar on my 40x objective anywhere from 0,13 mm to 0,185 mm.
Thanks!
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 8:51 am
by 75RR
.
I would assume that the slightly thinner cover slips are to compensate for the mounting medium, as I imagine that there is a thin layer between the diatoms and the cover glass.
Edit: Just read the instructions on the linked page - which seem to be instructions for making a diatom strew slide.
Don't know how different the procedure for arranged diatoms is ...
"Using a pipette, carefully place up to 1 ml of clean diatom slurry on each coverslip.
Take care not to disturb the coverslips and allow the diatoms to settle and the water to evaporate, at room temperature.
Coverslips usually dry overnight, but the amount of time depends on the ambient humidity.
When the coverslips are dry, place the aluminum plate on a hot plate (~ 130 C) to drive off remaining moisture.
Place a drop of mounting medium on a glass slide. Using the forceps, invert the coverslip with the diatoms (turn it diatom-side-down), and place it on the glass slide."
Curiously there does not appear to be any mounting medium between the glass slide and the diatoms - I had assumed that the diatoms were immersed in the high refractive index medium (thought that was the point), yet it appears that the diatoms only rest on it.
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 10:05 am
by Hobbyst46
75RR wrote: ↑Sun May 17, 2020 8:51 am
...Curiously there does not appear to be any mounting medium between the glass slide and the diatoms - I had assumed that the diatoms were immersed in the high refractive index medium (thought that was the point), yet it appears that the diatoms only rest on it.
1. Since diatoms are porous, and not sealed "glass boxes", solvent from the resin (IPA if Pleurax, toluene if Naphrax, etc) and the resin itself (especially when hot) can diffuse into and through the diatom and form a very thin layer in between the diatom and glass. In fact, some recommend to place a drop of solvent on the diatom layer on the cover slip, prior to addition of the resin.
2. To prepare arranged slides, a very thin layer of cement is speared on the coverslips and the diatoms are arranged on it (possibly sink somewhat into it). The mountant is added afterwards.
I doubt if anyone has identified, from the image of a diatom shown by a light microscope, the status of the space between the diatom and the coverslip - is it air, resin, cement...
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 11:24 am
by 75RR
Hobbyst46 wrote: ↑Sun May 17, 2020 10:05 am
75RR wrote: ↑Sun May 17, 2020 8:51 am
...Curiously there does not appear to be any mounting medium between the glass slide and the diatoms - I had assumed that the diatoms were immersed in the high refractive index medium (thought that was the point), yet it appears that the diatoms only rest on it.
1. Since diatoms are porous, and not sealed "glass boxes", solvent from the resin (IPA if Pleurax, toluene if Naphrax, etc) and the resin itself (especially when hot) can diffuse into and through the diatom and form a very thin layer in between the diatom and glass. In fact, some recommend to place a drop of solvent on the diatom layer on the cover slip, prior to addition of the resin.
2. To prepare arranged slides, a very thin layer of cement is speared on the coverslips and the diatoms are arranged on it (possibly sink somewhat into it). The mountant is added afterwards.
I doubt if anyone has identified, from the image of a diatom shown by a light microscope, the status of the space between the diatom and the coverslip - is it air, resin, cement...
So why do you think they are asking for a #1 cover slip?
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 11:51 am
by Hobbyst46
75RR wrote: ↑Sun May 17, 2020 11:24 am
...So why do you think they are asking for a #1 cover slip?
In the book "An Introduction to the Microscopical Study of Diatoms" by Robert B. McLaughlin, coverslips #1.5 are recommended.
in the
www.modernmicroscopy.com, article 107 "How To" Tutorial Series : The Collecting, Cleaning, and Mounting of Diatoms by Walter Franchini,
Coverslips of 0.16-0.18mm are suggested.
In the article: Diatom Arranging - Different Strokes, By Steve Beats - June 2015, the text does not mention, but the photo of necessary materials shows only #1.5 coverslips.
In the article: A Method for Cleaning Diatom Samples and the Preparation of Select and Strewn Mounts, By Stuart R. Stidolph (new Zealand)
#1.5 coverslips are suggested.
Just citations, nothing that I personally know.
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 12:03 pm
by Wes
Good discussion, I think #1.5 it is then!
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 12:09 pm
by MicroBob
He is a short introduction into a simple diatom arranging technique in german language:
http://www.mikrohamburg.de/Programm/Pro ... 170218.pdf
You need the right combination of mounting adhesive, sticky layer and mountant.
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 12:56 pm
by MichaelG.
Thanks for that, Bob ... I will see what DeepL makes of it
MichaelG.
.
Edit: Looks pretty good, but will need doing in two batches.
Re: What coverslip thickness for permanent diatom slides
Posted: Sun May 17, 2020 1:01 pm
by 75RR
A quick google translate of a relevant paragraph in MicroBob's linked article:
"The high refractive index mounting media do not run particularly well, so the recommendation is to use small round coverslips.
The cover glasses should adhere as closely as possible to 0.17mm to enable the best resolution when viewing."
I think it likely that as #1.5 and #1.5H cover slips are expensive, the original posting sensibly recommended the cheaper #1 cover slips for the diatom strew slides.
It is also possible that as strew slides tend to look somewhat like pick up sticks, a little less distance (thinner cover slips) is not a bad thing.
Re: What coverslip thickness for permanent diatom slides
Posted: Tue May 19, 2020 9:13 pm
by Wes