Diatom selection experience
Re: Diatom selection experience
Thanks 75RR !
Re: Diatom selection experience
I would have great difficulty trying to provide a convincing technical description of the process ... But, intuitively, that seems very reasonable.Hobbyst46 wrote: ↑Wed Sep 09, 2020 3:46 pm[…] it appears that for some reason, wet diatoms attach better (to glass) than dry diatoms. Perhaps, this holds for gently cleaned frustules, that still contain trace amounts of protein or other organic residue that may function as adhesive. But it worked for me with chemically cleaned fossil diatoms as well.
I’m sure that adhesion and cohesion [see, surface tension] are your friends.
MichaelG.
Too many 'projects'
Re: Diatom selection experience
No way I can prove this process...MichaelG. wrote: ↑Wed Sep 09, 2020 9:26 pmI would have great difficulty trying to provide a convincing technical description of the process ... But, intuitively, that seems very reasonable.Hobbyst46 wrote: ↑Wed Sep 09, 2020 3:46 pm[…] it appears that for some reason, wet diatoms attach better (to glass) than dry diatoms. Perhaps, this holds for gently cleaned frustules, that still contain trace amounts of protein or other organic residue that may function as adhesive. But it worked for me with chemically cleaned fossil diatoms as well.
I’m sure that adhesion and cohesion [see, surface tension] are your friends.
MichaelG.
On the one hand, the most remarkable mounted diatom artworks dating from so many decades indicate, that it is possible to arrange and mount them densely and in a particular order on the glass surface, then make it permanent.
On the other hand, mounting with a resin, that needs 180C to harden, along with the boiling of the solvent, seems to be complex. How can an the adhesive fulfill all demands:
adhere strongly to the glass AND to the frustules even under these high-temp conditions -
- stay transparent
do not fill the frustules
do not lower the refractive index too much
do not crystallize or form lumps
do not discolor
have a decent shelf-life
be easy to evenly spread
My experience stems from a limited number of experiments. Just laying the diatoms on a dry coverslip, then mounting in Pleurax, sent them far away beyond the borders of the coverslip. Exactly as previously mentioned by Charles. Methods a and b above provided a viable though not ideal solution.
The polyacrylamide adhesive might work better; however, the stuff is very expensive and the shelf life of the liquid is limited.
Re: Diatom selection experience
Sorry, Doron ... I’m confused by your latest post
It quotes my response to a previous one, but that seems irrelevant to what you are saying.
Apologies if I am missing something
MichaelG.
It quotes my response to a previous one, but that seems irrelevant to what you are saying.
Apologies if I am missing something
MichaelG.
Too many 'projects'
Re: Diatom selection experience
The polyacrylamide adhesive works, I tested it. Whats not mentioned in this link is that he uses a special anionic PAM variant. I however used regular PAM and it worked really well.Hobbyst46 wrote: ↑Wed Sep 09, 2020 7:48 pmThanks Bob, I stand corrected ! it is far apart... yet both substances are soluble in water and not in alcohol (or at least, much less in alcohol). The amide chemical groups makes them so.MicroBob wrote: ↑Wed Sep 09, 2020 7:26 pmHi Doron,
nice to hear of you progress!
According to your note 2: Michel Haak suggests polyacrylamide, not polyamide. I'm no chemist and don't know how far this is apart. http://www.diatoms.eu/de/node/77
The high curing temperature of Pleurax really narrows down the number of possible candidates for adhesives.
Bob
Zeiss Photomicroscope III BF/DF/Pol/Ph/DIC/FL/Jamin-Lebedeff
Youtube channel
Youtube channel
Re: Diatom selection experience
Good news, thanks ! I thought that any ionic substance is bound to crystallize or form lumps. Sigma-Aldrich prices for polyacrylamide are very high.Wes wrote: ↑Thu Sep 10, 2020 12:42 pmThe polyacrylamide adhesive works, I tested it. Whats not mentioned in this link is that he uses a special anionic PAM variant. I however used regular PAM and it worked really well.Hobbyst46 wrote: ↑Wed Sep 09, 2020 7:48 pmThanks Bob, I stand corrected ! it is far apart... yet both substances are soluble in water and not in alcohol (or at least, much less in alcohol). The amide chemical groups makes them so.MicroBob wrote: ↑Wed Sep 09, 2020 7:26 pmHi Doron,
nice to hear of you progress!
According to your note 2: Michel Haak suggests polyacrylamide, not polyamide. I'm no chemist and don't know how far this is apart. http://www.diatoms.eu/de/node/77
The high curing temperature of Pleurax really narrows down the number of possible candidates for adhesives.
Bob
BTW - another advantage of the "water adhesive" over gelatine is that the background is fairly clean, gelatine showed various artifacts, perhaps tiny cracks. These were formed during application, since the gelatine adhesive itself was filtered through a 0.45um filter prior to use. Admittedly the gelatine was ~2% in strength, whereas the final strength of the polyacrylamide adhesive is ~0.004% as described by M. Haak.
Re: Diatom selection experience
Hi Doron,
for your single diatom mouts I had another idea: You might set the diatom in a tiny drop of Pleurax on a cover slip and cure it. Then mount the cover slip on the slide with a different mountant that doesn't need a bubbling curing action, like an UV glue. This way you would be sure that the diatom will be in the tiny spot of Pleurax.
Bob
for your single diatom mouts I had another idea: You might set the diatom in a tiny drop of Pleurax on a cover slip and cure it. Then mount the cover slip on the slide with a different mountant that doesn't need a bubbling curing action, like an UV glue. This way you would be sure that the diatom will be in the tiny spot of Pleurax.
Bob
Re: Diatom selection experience
I see bubbling mentioned a lot with these diatom mountants -- is it necessary for some physical/chemical reason, or is it just difficult to remove the solvent in a reasonable amount of time without bubbling?
Re: Diatom selection experience
It is difficult to remove the solvent within a reasonable time period without boiling. Every 10C difference in temperature implies lengthening the time by roughly X 2.5.
Re: Diatom selection experience
Update:
Gelatin works too, but only when it is freshly made, and the gelatin coated slides are not as clean, so PAM is recommended.
After many more isolated diatom preparations, my results are indeed that PAM works well, and is compatible with Pleurax, although the exact positioning of the diatoms relative to one another on the slide is unimportant for me.
Gelatin works too, but only when it is freshly made, and the gelatin coated slides are not as clean, so PAM is recommended.
Re: Diatom selection experience
Did you synthesize the PAM yourself and procured it from a commercial source?Hobbyst46 wrote: ↑Sun Jun 13, 2021 3:59 pmUpdate:
After many more isolated diatom preparations, my results are indeed that PAM works well, and is compatible with Pleurax, although the exact positioning of the diatoms relative to one another on the slide is unimportant for me.
Gelatin works too, but only when it is freshly made, and the gelatin coated slides are not as clean, so PAM is recommended.
Zeiss Photomicroscope III BF/DF/Pol/Ph/DIC/FL/Jamin-Lebedeff
Youtube channel
Youtube channel
Re: Diatom selection experience
It is a commercial product, from Sigma perhaps, got a tiny sample from a friend. Prepared a concentrated stock solution. Dilute and filter to make the adhesive. The adhesive still works OK after 3 months storage in a stoppered vial at room temperature (here, around 20-25C most of the time so far).
Re: Diatom selection experience
Just asking cause I always prepared it fresh by polymerizing acrylamide and I am not too keen on working with acrylamide. Never tested the shelf life tho. Could you link the exact product from Sigma?Hobbyst46 wrote: ↑Fri Jun 18, 2021 9:46 amIt is a commercial product, from Sigma perhaps, got a tiny sample from a friend. Prepared a concentrated stock solution. Dilute and filter to make the adhesive. The adhesive still works OK after 3 months storage in a stoppered vial at room temperature (here, around 20-25C most of the time so far).
Zeiss Photomicroscope III BF/DF/Pol/Ph/DIC/FL/Jamin-Lebedeff
Youtube channel
Youtube channel
Re: Diatom selection experience
I was told that it is Sigma 92560 non-ionic PAM. Very old package. A tiny amount suffices for many slides. The Sigma catalogue appears to specify a MW of 5*10^6 or so. It swelled in water, and I brought to solution by heating.