Diazo gelatin (DIAG)

Dichromated Gelatin.
Martin
Posts: 121
Joined: Sat Apr 04, 2015 2:36 am

Diazo gelatin (DIAG)

Post by Martin » Tue Oct 22, 2019 3:54 am

Just noticed that I might have had it wrong about D.A.S. (diazidostilbene-2,2'-disulfonic acid salt), diazo gelatin ("DIAG") - see https://holographyforum.org/forum/viewt ... 0&start=30.

Luckily, I had some ethanol D.A.S. solution left, which I had kept in my fridge for more than six years. I sensitized some Gelita culinary gelatin and let it dry. The layer looked somewhat "dirty" because a large part of the D.A.S. had precipitated out.

In my early diazo gelatin attempts I erroneously applied a similar processing scheme I had standardized with FEG layers, that's to say, H2O2 (occasionally persulfate or permanganate), water, alcohol. I now see it's a far better idea to start with an alkali bath (e.g. potassium carbonate solution).

So the holographic exposure ought to be done at 405nm (possibly up to 450nm or so). Then, the plate is inserted into an alkali solution, washed and dehydrated just like DCG. I don't know if this stuff can be spectrally sensitized though. On the samples exposed at 405nm I saw evidence for very strong index modulation, definitely on the level of DCG or FEG. It was somewhat tricky to judge because I have a 405nm diode with very short coherence length and heavy mode-hopping (hence I'm still looking forward to seeing these problems addressed by the laser guys here hopefully). Speed is in the DCG/FEG range. But processing has yet to be optimized.

In the light of this finding I wonder about the Speedball material "VASIMV" mentioned earlier this summer. As of now I was unable to get it delivered to my home country. So currently, I keep looking out for alternative diazo materials.

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Diazo gelatin (DIAG)

Post by vasimv » Tue Oct 29, 2019 6:47 pm

Interesting. I'm busy experimenting with dye+TEA/TMG (no dichromates) emulsions now and got good holograms with it last week but plan to return to experiments with FEG and speedball diazo stuff some time later.

Do you think the DIAG stuff compatible with dye+TEA or TMG sensitizing? Seems it has high pH on its own and shouldn't bleach dyes. I've managed to start green osram PL530 laser with peltier cooling and it looks much better than 405nm diodes (both in power and quality) and very interested in any stuff that can increase sesntivity of dye+TEA/TMG recipes.

Martin
Posts: 121
Joined: Sat Apr 04, 2015 2:36 am

Re: Diazo gelatin (DIAG)

Post by Martin » Thu Oct 31, 2019 3:05 am

vasimv wrote:
Tue Oct 29, 2019 6:47 pm
Interesting. I'm busy experimenting with dye+TEA/TMG (no dichromates) emulsions now and got good holograms with it last week but plan to return to experiments with FEG and speedball diazo stuff some time later.
That's amazing. What's your gelatin? The last time I tried this with my standard gelatin I was only able to record some dim transmission gratings.

Meanwhile, I had some success with dye sensitized FEG + monomer. I hope to post more on this soon.
Do you think the DIAG stuff compatible with dye+TEA or TMG sensitizing?


I don't know about other diazos but with D.A.S. TEA or TMG are not compatible. But I seem to remember spectrally sensitized diazo materials mentioned by Kosar's book.
I've managed to start green osram PL530 laser with peltier cooling and it looks much better than 405nm diodes (both in power and quality) and very interested in any stuff that can increase sesntivity of dye+TEA/TMG recipes.
The PL530 is good news. Is there a way of purchasing a system (being completely illiterate in regards to electronics)? Yet I'd love to see also a 405nm laser of decent quality/at a reasonable price.

As for speeding up your process, you might add a monomer to your solution. I got decent holograms with good speed when adding acrylamide and methylenebisacrylamide to the gelatin-TMG-dye solution. The holograms were extremely sensitive to humidity though. Of course, we'd have to find less hazardous monomers compatible with gelatin...

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Diazo gelatin (DIAG)

Post by vasimv » Thu Oct 31, 2019 8:02 am

Martin wrote:
Thu Oct 31, 2019 3:05 am
That's amazing. What's your gelatin? The last time I tried this with my standard gelatin I was only able to record some dim transmission gratings.
Well, it is one of my alchemy attempts, i've mixed safranin O dye, TEA and TMG (2 times more than TEA) in same emulsion (from my previous experience - TEA provides good holograms but weak sensitivity and TMG increases contrast and sensitivity but weak holograms alone). This should work with Methylene blue too but my red laser is quite weak to test as the emulsion requires many hundreds of mJ/cm2 exposure. Later i plan to test if i do really need TEA as my success could be just because i've got right pH adjustment with the recipe. The gelatin is "Superclear 300 bloom" - https://www.amazon.com/gp/product/B00FGZAXII

Best i've got so far with TEA/TMG (had to underexpose it a bit as it tends to do big blue shift in good exposed areas, perhaps because high concetrations of TEA+TMG):
DSC_2024.JPG
DSC_2024.JPG (142.03 KiB) Viewed 6326 times
Martin wrote:
Thu Oct 31, 2019 3:05 am
I don't know about other diazos but with D.A.S. TEA or TMG are not compatible. But I seem to remember spectrally sensitized diazo materials mentioned by Kosar's book.
Hmm. May be just add a dye to the DAS emulsion? The speedball diazo has some dye in it but looks like it was optimized for far-blue region.
Martin wrote:
Thu Oct 31, 2019 3:05 am
The PL530 is good news. Is there a way of purchasing a system (being completely illiterate in regards to electronics)?
I didn't found cheap ready systems with it. So, i've just made one with 2 switching regulators, peltier module, thermoresistor, arduino and MOSFET+LC filter (one regulator sets current for laser, other for its heater element and arduino with MOSFET regulates voltage on peltier module to keep laser assembly's temperature at 25C with 0.1C precision). Perhaps not good idea to use switching regulator for the laser diode (voltage ripples may cause diode's mode switching) but looks ok. I plan to make final version soon (fully made of assembled regulator modules and microcontroller board) which should be easy to assemble by anyone who can use a soldering iron, will post it on forum when ready. Full price for the stuff would be in $120..150 range.
Martin wrote:
Thu Oct 31, 2019 3:05 am
Yet I'd love to see also a 405nm laser of decent quality/at a reasonable price.
Seems only way is to buy 100..300 mW diodes and run them on very low power with good cooling to get some quality. There are crystals that could be used to increase laser frequency (like in green lasers) to make DPSS UV-laser but i haven't found cheap ready modules with it. :(
Martin wrote:
Thu Oct 31, 2019 3:05 am
As for speeding up your process, you might add a monomer to your solution. I got decent holograms with good speed when adding acrylamide and methylenebisacrylamide to the gelatin-TMG-dye solution. The holograms were extremely sensitive to humidity though. Of course, we'd have to find less hazardous monomers compatible with gelatin...
Sodium acrylate (NaO) perhaps? People use it as direct replacement of acrylamide in photopolymer systems. But i wasn't able to obtain some. :(

Martin
Posts: 121
Joined: Sat Apr 04, 2015 2:36 am

Re: Diazo gelatin (DIAG)

Post by Martin » Fri Nov 01, 2019 3:49 am

vasimv wrote:
Thu Oct 31, 2019 8:02 am

Well, it is one of my alchemy attempts, i've mixed safranin O dye, TEA and TMG (2 times more than TEA) in same emulsion (from my previous experience - TEA provides good holograms but weak sensitivity and TMG increases contrast and sensitivity but weak holograms alone). This should work with Methylene blue too but my red laser is quite weak to test as the emulsion requires many hundreds of mJ/cm2 exposure. Later i plan to test if i do really need TEA as my success could be just because i've got right pH adjustment with the recipe. The gelatin is "Superclear 300 bloom" - https://www.amazon.com/gp/product/B00FGZAXII

That's kind of a surprise. I'd have expected some alkali-treated cow gelatin, which was said to work best with TMG. Maybe the high Bloom of your gelatin is also important here.
My standard culinary gelatin is much less viscous - maybe around 200 Bloom.
DSC_2024.JPG
Impressive!

Hmm. May be just add a dye to the DAS emulsion? The speedball diazo has some dye in it but looks like it was optimized for far-blue region.
I tried a couple of dyes but didn't notice any sensitizing effect.

I didn't found cheap ready systems with it. So, i've just made one with 2 switching regulators, peltier module, thermoresistor, arduino and MOSFET+LC filter (one regulator sets current for laser, other for its heater element and arduino with MOSFET regulates voltage on peltier module to keep laser assembly's temperature at 25C with 0.1C precision). Perhaps not good idea to use switching regulator for the laser diode (voltage ripples may cause diode's mode switching) but looks ok. I plan to make final version soon (fully made of assembled regulator modules and microcontroller board) which should be easy to assemble by anyone who can use a soldering iron, will post it on forum when ready. Full price for the stuff would be in $120..150 range.
Not bad!
Seems only way is to buy 100..300 mW diodes and run them on very low power with good cooling to get some quality. There are crystals that could be used to increase laser frequency (like in green lasers) to make DPSS UV-laser but i haven't found cheap ready modules with it. :(
I wondered about this kind of filters: www.coherent.com/lasers/laser/powerlocker
Sodium acrylate (NaO) perhaps?
Yes, that would be a monomer to try. One difficulty is to find out about its compatibility with gelatin. The research groups in Dublin and Alicante don't look particularly interested in gelatin systems.

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Diazo gelatin (DIAG)

Post by vasimv » Fri Nov 01, 2019 8:27 am

Martin wrote:
Fri Nov 01, 2019 3:49 am
I tried a couple of dyes but didn't notice any sensitizing effect.
Found the patent for spectrally sensitized diazo by adding "dithiocarbamates" with dye: https://patents.google.com/patent/US3778274

There are some dithiocarbamates with low toxicity available for purchase even on amazon (like https://www.amazon.com/HiMedia-GRM4482- ... B00DYOBYBI but this one didn't mentioned in the patent).
Martin wrote:
Fri Nov 01, 2019 3:49 am
I wondered about this kind of filters: www.coherent.com/lasers/laser/powerlocker
Interesting, but if i understand correctly - bandwidth of these ones are too wide still. Their typical 0.03nm bandwidth is about 1.7mm coherence length. Would be nice addition to DPSS laser but alone wouldn't do much.

Martin
Posts: 121
Joined: Sat Apr 04, 2015 2:36 am

Re: Diazo gelatin (DIAG)

Post by Martin » Sat Nov 02, 2019 4:21 am

vasimv wrote:
Fri Nov 01, 2019 8:27 am

Found the patent for spectrally sensitized diazo by adding "dithiocarbamates" with dye: https://patents.google.com/patent/US3778274

Interesting. The question though is if the diazo materials mentioned in this patent are available and
compatible with gelatin.

Interesting, but if i understand correctly - bandwidth of these ones are too wide still. Their typical 0.03nm bandwidth is about 1.7mm coherence length. Would be nice addition to DPSS laser but alone wouldn't do much.
I was thinking of improving mode stability/coherence length of a cheap 405nm diode...

Martin
Posts: 121
Joined: Sat Apr 04, 2015 2:36 am

Re: Diazo gelatin (DIAG)

Post by Martin » Sat Nov 02, 2019 4:39 am

Martin wrote:
Sat Nov 02, 2019 4:21 am
I was thinking of improving mode stability/coherence length of a cheap 405nm diode...
See: https://www.coherent.com/assets/pdf/Sin ... torage.pdf

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