My new "wet" diatom adhesives - Looking for testers and feedback

Bill Dailey

7/24/23   #5521

Edited 7/30/23

For the last several months I’ve been messing with several wet diatom adhesives including Klaus’ (who actually used Meakin’s dextrine/glycerine but threw in some acetic acid  to make it last longer. Note that Klaus didn't actually use his tragacanth gum mess which he told everyone to make!), polyvinyl alcohol(PVA)/glycerine/isopropanol/isobutantol, and Debes/Beats/Downing (this is gelatin with added glycerine and is based on Beats’ revised Debes adhesive but with glycerine first reported on the Diatom Forum by Craig Downing in 2015: https://groups.io/g/diatom-forum/message/3254).

I've found that both the PVA/glycerine and the gelatin/glycerine adhesives work very well. I would like to get other peoples feedback so I can make any improvements to make it even better. The key to getting both methods to work without showing adhesive in the final mounts is to make the adhesive coating very, very thin. This requires flaming the cleaned coverslip before adding the diluted adhesive. I use a product called ROR (residual oil remover) available from eBay (https://www.ebay.com/itm/143623380581) or on Amazon (https://www.amazon.com/dp/B01LZBMI73/) to clean the covers and slides. I made a couple short video tutorials on flaming the cover and adding the adhesive that I have added to the Technique section of the Files section.

Right now my favorite wet adhesive is Debes/Beats/Downing (gelatin/glycerine) but other mounters like the PVA/glycerine formula.

Gelatin/glycerine formula:

Make a stock solution of 0.3 grams gelatin mixed in 1.0 mL of distilled water and then dissolve this in 25 mL of glacial acetic acid. (This is Beats’ solution)

Make a stock solution of 2:1 isopropanol/isobutanol.

To make the adhesive for use:  Add 2.0mL of the gelatine/acetic acid solution, 0.10mL of glycerine, and 2.5 mL of the alcohol mixture. I store this in a small vial that has a septum through which I pushed an open capillary tube. I use the capillary tube to add the small drop to the cover.

Clean you cover well, then flame it (very important-see video). Place cover on clean surface and add small drop of adhesive via capillary. If your cover was clean and well flamed, the adhesive should quickly flow to the edges, except where you held the cover with the tweezers. Let the acetic acid and alcohols evaporate for 15 minutes. However you can keep it overnight and use it the next day too. I've not tested now long the adhesive will stay.

To use the coated cover, I add a very small spot of glycerine on a slide and place the cover on that to hold it. Arrange your forms. When finished you can push the cover to the edge of the slide carefully with tweezers, then grab the edge of the cover with the tweezers and remove from the slide. I set the adhesive by running it through an alcohol flame a couple times but you can also use a hot plate set to 170-200 for 15-30 minutes or so. Then mount the cover.

Polyvinyl alcohol(PVA)/glycerine formula:

I obtained PVA inexpensively from eBay here: https://www.ebay.com/itm/193262811442

Stock solutions:

Make a solution using 0.4grams of PVA in 4.0mL glycerin and 10 mL glacial acetic acid. This requires heating and mixing for a day or two to get all the crystals into solution.

Make a 2:1 (volume/volume) mixture of isopropanol/isobutanol.

Use 0.1mL of this solution PVA/glycerine/acetic acid solution and dilute with 0.5mL glacial acetic acid and 0.5mL of a 2:1 mixure of isopropanol and isobutanol. I store this in a small vial that has a septum through which I pushed an open capillary tube. I use the capillary tube to add the small drop to the cover. (see video in the Files section under techniques).

Clean your cover well (I use ROR), then flame it (very important-see video). Place cover on clean surface and add small drop of adhesive via capillary. If your cover was clean and well flamed, the adhesive should quickly flow to the edges, except where you held the cover with the tweezers. Let the acetic acid and alcohols evaporate for 15 minutes. However you can keep it overnight and use it the next day too. I've not tested now long the adhesive will stay moist.

To use the coated cover, I add a very small spot of glycerine on a slide and place the cover on that to hold it. Arrange your forms. When finished you can push the cover to the edge of the slide carefully with tweezers, then grab the edge of the cover with the tweezers and remove from the slide. I set the adhesive by running it through an alcohol flame a couple times but you can also use a hot plate set to 170-200 for 15-30 minutes or so. Then mount the cover.

I believe that these adhesives may work for Pleurax, but I am so allergic that I dare not attempt it. Please let me know if you are able to test Pleurax with these adhesives.

I would appreciate any feedback from users of either method. Currently there are a couple diatomists trying these methods but the more the merrier!

As a final note: Since everyone uses different size cover glass and will have different size drops, etc, if you find that the adhesive layer is too thick after waiting overnight, then try diluting your adhesive mixture more using equal quantities of acetic acid and the 2:1 mixture of isopropanol/isobutanol.

Craig Downing

7/24/23   #5522

Hi Bill,

I got the original Beat's modified Debes recipe from his great article on Micscape in 2015 http://www.microscopy-uk.org.uk/mag/artjun15/sb-Diatom-Arranging.pdf

Craig

Rob Kimmich

7/24/23   #5523

Bill,

Excellent article and videos.

Thanks,

Rob

Bill Dailey

7/25/23   #5524

One of the things that I have no data on yet is how long these adhesive solutions, once mixed, will remain stable and usable. The chemist in me suggests that the PVA/glycerine should be stable indefinitely like Klaus' (Meakin's). The Debes/Beat/Downing (gelatin/glycerine) adhesive might suffer the same fate as the original Debes/Beats and lose its effectiveness in a few months because of some kind of changes to the gelatin. HOWEVER since I am curing the slide differently (heating hot) than the Debes/Beats method, I think that even "denatured" gelatin may still act as a good glue once all the solvent is removed by heating. So I have some confidence that it will also remain usable for a long period of time.

But I would appreciate feedback from others on any aspect of using these two formulas.

Bill

Anne Gleich

7/25/23   #5525

Dear Bill,

congratulation to this wonderful work. My or a general question for me is, what happens with the Glycerin? Boiling point is 290 degree Celsius.

best

anne

Bill Dailey

7/25/23   #5526

Edited 7/30/23

Hello Anne,

The glycerine "evaporates"! Just like water, which boils at 100C, evaporates at (or well below) room temperature, the same happens with the glycerine. Putting the cover through the alcohol flame, you can see the "puff" of glycerine evaporating. But it also evaporates even at a lower temperature (like 175 to 200C) on a hotplate in 15 to 30 minutes. Emiliano uses this method to cure his slides. I use the alcohol flame (because I am impatient). Try the adhesives and let me know what you think of them. I have found that for small covers (like 10mm) with small forms, a more dilute adhesive formula may be better. The last few times I have added some more acetic acid and the 2:1 alcohol mixture (maybe half as much total volume as was the original adhesive mixture) and this works well. You will have to try it and see how thick the coating of glycerine/gelatin is on the cover compared to the forms you want to mount. There can be some liquid showing on the forms as you move them, but they shouldn't be completely covered by the liquid adhesive or you may see some traces in the final mount. Your dilution will depend on how big your covers are (the area needed to be covered) and how big of the drops of adhesive that you add to the cover. So just do a few trials and see what you find. I have found that prepared covers can be used at least two days later (probably much longer but I haven't done it yet).

Best regards,

Bill

Edit:  Please try Pleurax for me!!

Craig Downing

7/26/23   #5527

Hi Bill,

I tried another quick arrangement of gold coated Oamaru rarer fragments and some complete forms froma strew slide using your exact procedure/recipe. Worked well. This time I baked off the coverslip on hotplate, unlike last time! All held well with fairly vigorous bubbling when heating the mounted slide.

When I tried this in 2015, I used Beats' recipe, but added more glycerine than what you specify ( a little less than the amount of isobutanol). Looks like less works better, but I could cook it off no problem. All of those slides have survived without problems.

I remember having problems with floating diatoms before using Pleurax, which I expected due to the alcohol solvent used, but I thought it could hold the diatoms in place, and with caution cure the mounting media with coverslip down (rest the slide on two blank slides on hotplate). I then got a hold of Naphrax, then Styrax which worked much better in that respect. I'll try again sometime with Pleurax.

Craig

Craig Downing

7/26/23   #5528

... forgot to mention those 2015 era slides I also mounted using Cargille Meltmount/toluene before trying Naphrax and Styrax, which have been stable since.... I haven't used Naphrax for a while as my jar of it has gone cloudy, and I can't find a way to get rid of the cloudiness.

Bill Dailey

7/26/23   #5529

Hi Craig,

Thanks! Sounds good. Yes, if you could try Pleurax on a really well-cooked (or even flamed like I do) cover that would be great. I THINK it will hold ok since Klaus' (Meakin's) dextrin/glycerine works fine with Pleurax. I'm assuming that the high heat "cooks" the gelatin into something different so it won't be as soluble in alcohol. But someone just needs to check it.

Concerning your cloudy Naphrax: sorry but when this happened when I made my Zrax, I just threw it out. I tried many, many, many ways to get the cloudy out and failed. I think it's some kind of phase-separated impurity. When you dissolve the Naphrax (or Zrax) in enough toluene it goes away, but when you remove the toluene it comes back. Makes for a snow-storm under darkfield!

I've also started a thread on the German Mikroskopie-forum if anyone would like to follow that. I use Google translate or DeepL as a translator since my 2 years of German for scientific reading knowledge is long gone. The thread is here:  https://www.mikroskopie-forum.de/index.php?topic=46912.0

Bill

Craig Downing

7/27/23   #5530

Hi Bill,

I made a small 7 form cross arrangement this afternoon with gold coated Oamaru diatoms. A couple of Coscinodiscus and a nice Aulacodiscus (kittoni?) plus a few others. This time I tried Pleurax. Two floated away: The Aulacodiscus which was qiute well seated on the rim and a small cup shaped centric which was attached on the surface rather than edge and I could see a rung of wet adhesive when I plonked it down in place. Could be they were going to go off in a toluene diluted resin, but they seemed pretty secure to me, so I don't think so. I baked the crap out of the coverslip on the hotplate at 275 oC for about 20minutes. Have been curing on hotplate inverted for 2hrs, will leave for a while more.

Craig

Bill Dailey

7/27/23   #5531

Thanks Craig. So 5 out 7 stayed attached? That's a good start!

Bill

Craig Downing

7/30/23   #5542

Hi Bill,

Finally, success! I spent this afternoon picking over a single dilute strew of your cleaned Dunkirk material on a 22x22mm coverslip, then arranging in my best effort at a circle of 38 of the most interesting/complete forms. As the sample is so rich and your cleaning so well done, there was plenty just from that. Probably could find about 10% of the strew without breakages.

I used the modified Debes with glycerol. Cured on hotplate at around 130 oC for 15-20min or so, then mounted in medium using toluene as solvent. No problem this time. Had the slide inverted to boil of solvent for over 6 hours and bubbles were coming out until almost the end, but all stayed in place.

Craig

Bill Dailey

7/30/23   #5544

Hi Craig,

Looks good! Can you try Pleurax again the same as this?

Bill

Craig Downing

7/30/23   #5545

Will do, once I build up the courage! Getting my skills back up to speed....

I noticed Pleurax often tends to "pop" lifting the coverslip up, perhaps due to the lower boiling point of isopropanol vs toluene? This may be causing the problems I had with the previous attempt. If the temperature is low to start curing the slide then it also tends to seal from the outside slowing evaporation of the solvent it appears. SO I have found it a bit tricky to get the temperature right. I have been using about 120 - 125 oC on the hotplate.

Bill Dailey

7/30/23   #5546

Edited 7/30/23

Craig,

Yes, isopropanol boils much lower (82C) than toluene(110C) so you should lower your hotplate temperature by 30 degrees to cure Pleurax slides to avoid overly vigorous bubbling. I'd start at 80C and see how it goes, then slowly increase to maybe 100C. Vigorous bubbling with Pleurax can be a problem.

You might consider Beats' method (Beats please chime in here!). He adds a small amount of slightly diluted mountant to the forms on the cover which is placed on the warm (not hot) hotplate and lets the solvent slowly evaporate. Because it is open to the air, the solvent doesn't form bubbles or if it does they head straight up and don't move the forms. Once the solvent is gone he adds the slide onto the mountant drop. I have never used this technique so I don't know how difficult it is. But I can image that you have to be very careful not adding too much mountant or it will go everywhere. You might want to try with blank cover slips for a few tries.

Bill

Craig Downing

7/31/23   #5550

Hi Bill,

Thanks, I did try Beats' method a few years ago to avoid bubbles. Did not do that this time. I just made another small arrangement and mounted in Pleurax. This time I did the same curing adhesive on coverslip on hotplate at around 130-140 oC for about 15mins. Once mounted, very slowly raised temp from 80 to about 100 oC with coverslip down so it bubbled very gently. THe slide I made before with Pleurax "popped" so that no doubt helped dislodge a couple of diatoms. So far so good, let's see how it turns out in a couple of hours!

Craig

Craig Downing

7/31/23   #5551

Worked out fine, nothing shifted! https://groups.io/g/diatom-forum/photo/287584/3658511?p=Name%2C%2C%2C20%2C1%2C0%2C0

Bill Dailey

7/31/23   #5552

Excellent!! So the Debes/Beats/Downing adhesive can be used for both toluene-based AND alcohol-based mountants!!!!!

Great job Craig!

Bill

Anne Gleich

8/14/23   #5591

Dear Bill,

I tested the method today - it works for me with Pleurax.

It was important that the adhesive base with the diatoms on it is dried at a high temperature for a sufficiently long time. (thank you Bill for this tip)

I first dried at about 130°C for 30 min, which was not enough.

When drying at 190-200°C for about 40 min, the diatoms were no longer detached from the Pleurax.

I cannot say whether it works at 160°C, for example.

Thank you Bill for assisting me in the background.

anne

Craig Downing

1/12/24   #5931

Hi Bill,

I got my hands on some PVA from the source you identified and mixed up a batch per your recipe. I was wondering if the reason you show a small volume of final solution ready for use (~1ml) vs the Debes recipe was maybe due to expectation in the self life of the adhesive? But then I see in your post that you would expect a long shelf life for the mixed PVA adhesive. I mix these up in 4ml autosampler vials, as I have a box of them handy. Even then 3-4ml is a lot. A batch of Debes from July is now cloudy with a thick deposit on the bottom of the vial of a mm or two - I just had it out on my "lab" bench, so at room temp in the basement with a little UV coming indirectly through small windows.

For Debes, is the degradation of the gelatin due to the alcohols, the esters forming with the acetic acid, or both perhaps?

I'll give the PVA glue a try this weekend if I get a chance - could try with Pleurax too. I just made a nice 39 form selection from the Newport material using the wet Debes last weekend. I cured inverted and it was perfect. However, no doubt due to something lacking in my process I had a couple of floaters after warming a little on hotplate the right way up (I wanted to level the coverslip)... aargh. Mind you they were large heavy diatoms such as a Campylodiscus (only one whole example I have found so far, in addition to a couple of fragments!) Still got some nice examples from that mounted up. Loads of variety in the small-mid range (20-60 micron sieved fraction).

Now I am thinking of trying out sputter coating some picked Newport diatoms...