Dry fusing diatoms to cover slip.

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Phill Brown
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Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Dry fusing diatoms to cover slip.

#1 Post by Phill Brown » Thu Jun 03, 2021 10:47 am

Did a search of this forum and didn't find this reference.
I am new to forums in general but like many here didn't hatch recently.
In a book from 1873 by Frederick Mills Dry mount method is attributed to an earlier book by a Mr Davies, that book is reprinted and available but the author is unlikely to be Mr Davies microscopist as apparently he was not given to writing.
Diatoms are added to a cover slip in a drop of water and allowed to dry.
No mention is made of arrangements but that should be possible?.
The cover slip is placed on a small platinum disc attached to a handle and held in the spirit lamp until a dull red.
This fuses the diatoms to the glass.
A mountant of choice can then be added without the diatoms moving and the cover slip mounted to the slide.

My musings are stainless steel could be substituted for platinum?
Oxide will contaminate the cover slip so platinum with 1600°c melting point may be optimal.
I have not tried this as I do not have access to cleaned prepared diatoms.

UK law PPE license required for H2O2 above 12%. Also Sulphuric above 15%.
I do not qualify for the PPE license so will need to work around it.
Any help with this issue would be a most welcome but should be a different thread. I could contribute by making precision parts in exchange.
Image
I have attached a picture of a cover slip holder I made. Easy to clean the cover slip,top part is a drop on fit that turns freely. Can rotate the cover slip under the microscope without moving the slide. The other,I place the cover slip into the circle which is centred. The cover slips either end are stuck with double sided plastic to space and align the slide. Image
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Suphot
Posts: 99
Joined: Wed Mar 11, 2015 4:35 am

Re: Dry fusing diatoms to cover slip.

#2 Post by Suphot » Sat Jun 05, 2021 1:37 pm

I did not fusing diatom on slide, but let it slowly dry under cover slip. It can kept diatom several months.

For details you may read my post from here;

https://www.microbehunter.com/microscop ... 10&t=12781

microbob comment that the diatom may be clean by using alcohol burner. I am not try it yet.

It may be work foryou.

Suphot

MicroBob
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Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Dry fusing diatoms to cover slip.

#3 Post by MicroBob » Sat Jun 05, 2021 2:14 pm

Hi Phill,
the heating process is used for burning off organic matter to clean the diatom for better visibility of the pores. The remaining dirt keps the frustule attatched to th ecover slip well enough, so colonies of diatoms stay in formation. The cleaning will be better with higher temperatures and longer duration but some diatoms will deform. Also the cover slip glass softens increasingly above 500°C and can deform.

I recently worked on improving this method:

- small rectangular cover slip cuttings, ca. 9x9mm
Deformation is no big issue with small coer slips and rectangular ones don't shatter as easily as round ones
- drop of fresh diatom sample, let dry
- heat on 3-4mm thick stainless steel plate with alcohol burner
- apply additional heat from above with small blue flame gas burner
- heat until there is a colour chane from black to light gray
- pick up cover slip, let cool a bit in air
- draw through HCl 25% or concentrated vinegar and water to remove ashes
- let dry
- mount in Pleurax or what you have

This works fairly well. It is not as clean as cleaning with harsh chemicals but good enough for slids that satisfy me.

Bob
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Hobbyst46
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: Dry fusing diatoms to cover slip.

#4 Post by Hobbyst46 » Sat Jun 05, 2021 3:45 pm

MicroBob wrote:...
Very lovely images. I especially like the darkfield ones.
"Phill Brown" wrote:...
Some old diatom cleaning and manipulation protocols are outdated, for example because they involve really dangerous procedures and materials.

There are plenty of relatively recent diatom manipulation sources.

Here is one:
https://www.mccrone.com/mm/an-introduct ... diatoms-2/

Here are three that combine practical experience with enjoyable reading
https://www.microbehunter.com/microscop ... oms#p26443
https://www.microbehunter.com/microscop ... 227#p38444
https://www.microbehunter.com/microscop ... oms#p80886

Here is another, that focused on cleaning by incineration, and shows some pitfalls (that MicroBob's recent protocol avoids)
https://www.microbehunter.com/microscop ... ion#p55443

Phill Brown
Posts: 603
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: Dry fusing diatoms to cover slip.

#5 Post by Phill Brown » Sat Jun 05, 2021 10:38 pm

Thanks for the links. I had read about burning off the organic components.
My preference is dark field for diatoms.
It's quite likely that the glass used for cover slips made in 1893 would have different properties.
The method in Mills book is specifically to fuse the diatoms to the surface of the glass.
I'll get some methylated spirits and dig out my spirit lamp.
Nitric acid was used to clean the diatoms.
The sections on how to make a camera for the microscope and a darkroom of one's bedroom makes me glad that some technologies have moved on.

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