First attempts at arranging diatoms

[Wes]

For a brief while now I've been entertaining the idea of making my own diatom arrangements. After reading different accounts on how its done and a bit of struggling I present you my very first attempts. Below are a few arranged diatoms that I collected from the nearby river, which I cleaned and then mounted in Pleurax. There is not particular logic behind the choice of forms and species, simply going around a strew and picking up stuff that looked kind of interesting. I find it very challenging to align them perfectly and very often in my attempts to do so I undo the previously arranged frustules which is very frustrating so I tend to let it slide.


There are mostly penate forms, and a few centrics. On the lower left I managed to mount the same species in a way that reveals the valve and girdle sides.


The big one looks like some kind of Surirella but I'm not entirely sure.


Cymbella with a first order wave plate.


Gyrosigma, actually from a previous slide I mounted. Its a stack of 8 images.

[Charles]

Good job Wes! Nicely done.

[75RR]

Impressed with all the hard work! Not sure yet if you have inspired me or frightened me away ;)

[Hobbyst46]

Magnificent ! impressive variety, beautiful display and neat arrangment. No chance I will ever try this...

[microb]

Really cool.

Would be great to see the steps taken, and the recipe for the mount on the cover slip.

[KurtM]

Really cool.

Would be great to see the steps taken, and the recipe for the mount on the cover slip.

^^^ I second the motion!

[Wes]

Thank you all for encouraging remarks!

Now to answer some of your questions. I boil the samples in 30% hydrogen peroxide with some hydrochloric acid followed by several washes with distilled water and finally the diatoms are resuspended in ethanol to prevent mold growth. I make a strew slide from the ethanol suspension and using a pulled glass needle I transfer the diatoms to another slide (in my case to an adhesive coated coverslip but would now start a keeper slide).

Since I used Pleurax my adhesive of choice was based on advice by Michel Haak who owns diatoms.nl. He suggested a polyacrylamide adhesivethat he had developed and so far it worked really well. Once I arrange the diatoms on the adhesive coated coverslip I breathe on it a few times to moisturize the surface and get the diatoms to firmly attach to the adhesive. I gently heat up the coverslip to 100˚ C and let it stay that way for some 10 minutes or so. When it cools down I add a small drop of isopropanol and while still wet I add the Pleurax. Initially I was making the mistake of adding not enough Pleurax which ultimately resulted in the coverslip crushing the diatoms. So I started adding the generous amount of 0.2 µl Pleurax per mm² of coverslip area (basically 50 µl per 18 mm round coverslip). I register the orientation of the arrangement and carefully put the coverslip on the heating unit. There I slowly start raising the temperature from 40 to 100˚ C. This drives off the solvent and the Pleurax thickens quite a bit. Then I simply flip the coverslip on to a clean slide on the same heating unit and gently raise the temperature up to 180˚ C. Once at that temperature I let it stay for 1-2 hours and then turn off the heater. Initially I was getting some bubbling but I managed to completely avoid it with the last attempts. Once it cools down the slide is ready. I am still not ringing the slides by might do so in the future.

[MicroBob]

Hi Wes,
that is a great first attempt at diatom mounting! Making diatom photos and studying them in detail is much easier with these arranged slides. For these uses it doesn't matter if there is an angle not quite right or a single frustule is not really in first class condition.
It really is difficult to check the individual frustule for it's condition and keep an overview when moving it with the same magnification. I used a 5:1 objective with 10:1 eyepiece ant this went so-so. Occasionally I precision mounted pieces of dirt.
As a mounting needle I used a baby seal hair from a 1970s winter boot. Hedgehog hairs( the spikey ones next to the spines are best) can also be used.
Also nice to hear of a Pleurax-compatible process! My Aroclor version will only be available as long as I can get Aroclor and the production is banned for decades.
Does that adhesive layer offer a certain initial tack to be able to get the diatoms off the needle?

Bob

[Wes]

Does that adhesive layer offer a certain initial tack to be able to get the diatoms off the needle?

Hi Bob! I don't think this particular adhesive offers that although I have not extensively compared it against a plain surface coverslip or other adhesives. In fact the adhesive layer itself is very thin, usually difficult if not impossible to see and only becomes visible after I breathe on it. It seems that electrostatic forces play a great role in making the diatoms stick to coverslip/adhesive surface or your needle, sometimes they stick to the needle and just don't want to let go. Other times they don't want to stick at all (certain species seems much easier to work with than others).

[charlie g]

Beautiful work, Wes! Thanks for this display of good microtech. charlie guevara BTW, I always wonded if I could collect and save the occasional huge pennate naturally cleared frustules I encounter in wetmounts from time to time...to one day try and mount these frustules.

Thanks again Wes for a wonderful thread,

[MicroBob]

It seems that electrostatic forces play a great role in making the diatoms stick to coverslip/adhesive surface or your needle, sometimes they stick to the needle and just don't want to let go. Other times they don't want to stick at all (certain species seems much easier to work with than others).

Hi Wes,
in the method I use the mounting fibre is made sticky with a tiny amount of skin fat. On the cover slip there are fine layers of shellac and skin fat. A diatom can be placed and moved into position but doesn't fly away in the lightest breeze. The guy I have this from researched Möllers methods in great detail. The Möller company still exists, about 25 km from here.

Here is a nice introduction video into diatom arranging: https://www.canal-u.tv/video/science_en ... e_1999.163

Bob

[Wes]

[/quote]

Beautiful work, Wes! Thanks for this display of good microtech. charlie guevara BTW, I always wonded if I could collect and save the occasional huge pennate naturally cleared frustules I encounter in wetmounts from time to time...to one day try and mount these frustules.

Thanks again Wes for a wonderful thread,

Thanks Charlie. You certainly can do that, you can perhaps wash the wetmount into a small container and store it till the time comes. Or move them manually, whichever works better for you.

It seems that electrostatic forces play a great role in making the diatoms stick to coverslip/adhesive surface or your needle, sometimes they stick to the needle and just don't want to let go. Other times they don't want to stick at all (certain species seems much easier to work with than others).

Hi Wes,
in the method I use the mounting fibre is made sticky with a tiny amount of skin fat. On the cover slip there are fine layers of shellac and skin fat. A diatom can be placed and moved into position but doesn't fly away in the lightest breeze. The guy I have this from researched Möllers methods in great detail. The Möller company still exists, about 25 km from here.

Here is a nice introduction video into diatom arranging: https://www.canal-u.tv/video/science_en ... e_1999.163

Bob

Cheers Bob, this adhesive would require the PCB mounting agent (Aroclor) right (to dissolve the finger grease)? Sounds pretty convenient for sure, this pinging effect with some diatoms drives me crazy. Also cool video, but I understand no French whatsoever.

I have now procured some rare samples from Oamaru and a few other places and have started the freeze-thaw cycles. So hopefully I can show you some interesting fossil diatoms soon.

Btw since we are on the topic does anyone know of a source of high precision coverslips? I have some 0,17±0,005 mm coverslips from Zeiss (18x18 mm) but would like to get round ones (wouldn't mind trading the Zeiss ones I currently have).

Wes

[Hobbyst46]

...Btw since we are on the topic does anyone know of a source of high precision coverslips? I have some 0,17±0,005 mm coverslips from Zeiss (18x18 mm) but would like to get round ones (wouldn't mind trading the Zeiss ones I currently have).

I have been using Menzel-Glaser coverslips, purchased a long time ago. Some suppliers carry them. The declared thickness is 0.16-0.19, I never checked it; but they are very clear and clean, unlike no-name cheap Chinese slips. Not the same cost of course.

[Wes]

Hm if I had a micrometer I could just bin them and select the 0.17 bin for cleaning and further processing.

[75RR]

Hm if I had a micrometer I could just bin them and select the 0.17 bin for cleaning and further processing

What you want is a Moore & Wright Micrometer No: 961MB

Here is one that sold recently: https://www.ebay.co.uk/itm/Moore-Wright ... _cvip=true which is accurate down to 0.002mm

Not expensive and there are usually a couple about, though not at this moment unfortunately. Bound to be one in the next week or two.

[MicroBob]

On german ebay there are lots of good used micrometers all the time. This was a product many companies tried to make money with in the 1950s and 1960s before the market concentrated on a couple of manufacturers. When used a lot, abused or dropped even theserobust measuring instruments become worthless. Basic professional grade is not expensive new: https://www.hoffmann-group.com/DE/de/ho ... e/p/420200

The best option for repetitive testing in a narrow range is this: https://www.feinmess-suhl.com/produkte/ ... aube-0537/

The micrometer was one of the most important inventions as it was very dependable and allowed repeatable measurements in the sub 0,1mm deviation range. Many good (and bad) things wouldn't have happened with out the micrometer!

Bob

[MicroBob]

http://www.o-kindler.de/deckglaeser.php ... eckglaeser

Kindler is one more cover slip maker. They say that they have other cover slips available, perhaps only in bigger amounts.

Your aim (precise and round) makes sense, especially for work intensive arranged slides.
I one bought round cover slips from China that were up to 0,25mm thick!

[Wes]

Thank you 75' and Bob

What about this one? https://www.ebay.co.uk/itm/Bugelmesssch ... SwenJaGCJe

Does it seem reasonable?

[Hobbyst46]

here is a Moore&Wright instrument
https://www.ebay.com/itm/Vintage-Moore- ... SwqjBe0sSB
And another
https://www.ebay.com/itm/Moore-And-Wrig ... SwXzBeN3Rd
In agreement with 75RR's forecast!
Mitutoyo micrometers, who I thought were top of the line, start at around 100USD on Amazon... why?

[75RR]

A micrometer that measures down to 0.01mm is not accurate enough, 0.002mm minimum is what you are after. Look for a 961MB

If you are going to measure your cover slips you need to be accurate.

MicroBob's recommendation to buy new and therefore potentially avoid the ware and tear of old equipment is valid, assuming the micrometer he is recommending is up to scratch.

[Hobbyst46]

Here is the M&W 961
https://www.ebay.co.uk/itm/Moore-and-Wr ... Sw5Ppc3Us4

[75RR]

Here is the M&W 961
https://www.ebay.co.uk/itm/Moore-and-Wr ... Sw5Ppc3Us4

Needs to be 961MB - that stands for metric and thousands, the one you show is inches.

[Wes]

Your aim (precise and round) makes sense, especially for work intensive arranged slides.

Other than ringing the cured slide on a ringing table is there any other particular reason to use round coverslips? I somehow doubt square coverslips would be much worse, but maybe I miss something here.

[MicroBob]

Hi Wes,
in my experience it is easier to completely fill the room under a round cover slip with mountant and get a half way nice looking slide. So for permanent slides I use round cover slips if at all possible. Along a ruler you could apply your ringing paint onto the edges of a rectangular cover slip too.

Micrometers: According to DIN 863 a micrometer 0-25mm has an allowed error of 4µm for the displayed value, 2µm for the parallelity of the measuring surfaces and 2µm for the elastic deformation due to the measuring force. So while it is possible to get readings below +/- 0,01mm to compare objects it will not be possible to get absolute measurements with more real accuracy. But we are already talking about a resolution that is in the range of the wave length of visible light!
This here would be a Mitutoyo one: https://www.hoffmann-group.com/DE/de/ho ... e/p/420500

Micrometers are not used as much today as they were a couple of decades ago when manualy controlled machines were the norm. So the very finest micrometers are not available any more as the makers have moved to products with more profit. But the ones you will get from Hoffmann and other reputable dealers will adhere to DIN 863 and measure correctly.
Enlosed is an image of some more interesting micrometers: Exchangable anvils, mechanical digital displays, extended range, a Feinzeiger micrometer, micrometers with 1mm per turn movement for quicker measuring, a big one.
For cover slips a basic one of dependable quality will do nicely. They were so successfull because they work after a simple principle and can withstand workshop use without going out of tolerance too easy. They follow Abbe's comaparator principle (he again!) that sais that for dependaple mesuring the scale and the measuring positions on the object have to be colinear. This makes the micrometer more dependable than a digital caliper.

Here is a nicely looking one: https://www.ebay.de/itm/Gewinde-Spindel ... 2444717437

Bob

[75RR]

What about this one? https://www.ebay.co.uk/itm/Bugelmesssch ... SwenJaGCJe

That looks nice, I would like to see the brand though.

[Hobbyst46]

This discussion amplified curiosity and it appears that <<0.01mm accuracy micrometers are being marketed, although prices are ~100USD. For example, by the firm Starret.
But, since we all own microscopes (by definition), and stereoscopes, there must exist a simple DIY optical trick to verify coverslip thickness, perhaps by comparing them all to a single "standard" 0.170mm coverslip. Newton rings or something...
Sorry, posted before I saw the link for a micrometer at 23 Euro.

[Wes]

What about this one? https://www.ebay.co.uk/itm/Bugelmesssch ... SwenJaGCJe

That looks nice, I would like to see the brand though.

Good point, not clear what the brand is (may explain the rather accessible price).

Maybe if one had a nice set of gauge blocks calibration would be easier.

[MicroBob]

One part of the testing of micrometers is actually done with an optical parallel. The numer of newton rings visible under monochromatic light is part of the specification. In use the anvils wear and won't pass the regular test any more. These micrometers are then sold on ebay.
The 0-25mm micrometers are tested and adjusted in the 0mm setting which is very close to cover slip thickness. Testing cover slips is comparatively undemanding as the whole anvil surface is used.

[75RR]

That is a nice collection MicroBob

I only have two, an inch one which I have had for years and a much newer to me metric one, as converting from inch to mm was inconvenient.

Here is a link that shows how to read a metric micrometer, includes instructions on reading a vernier which a 0.001 or 0.002 micrometer would have.

https://www.wisc-online.com/LearningCon ... LT3702.htm

[MicroBob]

The very expensive high tech swiss micrometer by TESA (top left) and Etalon (top right) have vernier scales to read in µm steps. On standard metric micrometers even from the best manufacturers I have never seen them in reality, while on imperial micrometers they are common. The scale on a metric micrometer is much finer than on an imperial one so probably people see them as superfluous. The TESA micrometers with the mechanical digital display are not really useful as the gears the drive the display take away some of the fine feel when using the micrometer. For my lathe I use the 0-50 micrometer most. While it is unwieldy it covers my most used diamterer range in one instrument.