Ferric ammonium oxalate tests

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

Re: Ferric ammonium oxalate tests

Post by vasimv »

I'm looking forward to learn about your tests.
In my experience adding citric (or tartaric, oxalic, lactic) acid didn't enhance speed.
Well, i've messed up my first batch and couldn't get samples good enough to compare them. But looks like citric acid does help a bit (not sure how much though). Will try to make new test by covering with already sensitized emulsion instead using sensitizer on gelatine layers and green laser instead near-uv one (which does produce something as gelatine stays on exposed areas but i can't see real hologram, possible because blue shift in UV area or just bad coherency of the laser).
Diazo was a direct replacement for Dichromate in gum and screen prints. From what I have read it was 2x faster as well.
How hard would it be to extend the spectral sensitivity of Diazo?
Going to try this with safranin-o and methylene blue dyes with speedball diazo emulsion when it arrives. There is also talks about another variant of the process with "4,4'-Diazidostilbene-2,2'-disulfonic acid, disodium salt, tetrahydrate" which gives even better results (https://www.photrio.com/forum/threads/a ... ive.99071/), but i couldn't find supplier for the chemical.
Martin
Posts: 131
Joined: Sat Apr 04, 2015 2:36 am

Re: Ferric ammonium oxalate tests

Post by Martin »

Grayham wrote: Tue May 21, 2019 12:46 pm Diazo was a direct replacement for Dichromate in gum and screen prints. From what I have read it was 2x faster as well.
You might search among the photoresists. I believe (???) Shipley started with diazos and later came up with hybrid diazo-photopolymer systems, which were much faster than the original one.
How hard would it be to extend the spectral sensitivity of Diazo?
I gathered that diazos required acid dyes for spectral sensitization. So methylene blue etc. can be ruled out.
Martin
Posts: 131
Joined: Sat Apr 04, 2015 2:36 am

Re: Ferric ammonium oxalate tests

Post by Martin »

vasimv wrote: Wed May 22, 2019 6:01 pm
I'm looking forward to learn about your tests.
In my experience adding citric (or tartaric, oxalic, lactic) acid didn't enhance speed.
Well, i've messed up my first batch and couldn't get samples good enough to compare them. But looks like citric acid does help a bit (not sure how much though). Will try to make new test by covering with already sensitized emulsion instead using sensitizer on gelatine layers and green laser instead near-uv one (which does produce something as gelatine stays on exposed areas but i can't see real hologram, possible because blue shift in UV area or just bad coherency of the laser).
Making contact copies from a transmission grating might simplify your tests.

As of now I never managed to record a hologram from a FEG layer. However, mixed layers of potassium chromate and FEG worked nicely. Curiously, they could be developed à la DCG (water swelling bath, alcohol dehydration) or à la FEG (H2O2 treatment, water wash, alcohol dehydration).


Going to try this with safranin-o and methylene blue dyes with speedball diazo emulsion when it arrives.


Do you happen to know the peak absorption wavelength of the Speedball diazo?
There is also talks about another variant of the process with "4,4'-Diazidostilbene-2,2'-disulfonic acid, disodium salt, tetrahydrate" which gives even better results (https://www.photrio.com/forum/threads/a ... ive.99071/), but i couldn't find supplier for the chemical.
I tried that one (you can get D.A.S. from alternative photo supplies). But it was very difficult to put a reasonable amount of D.A.S. into the gelatin. So light absorption at 405nm was pretty weak. Hence speed wasn't terrific. Moreover, the H2O2 "development" did rather poorly. I managed to get good holograms only with a potassium permanganate "developer".
Martin
Posts: 131
Joined: Sat Apr 04, 2015 2:36 am

Re: Ferric ammonium oxalate tests

Post by Martin »

Martin wrote: Thu May 23, 2019 3:04 am

As of now I never managed to record a hologram from a FEG layer.
Meant to say at 532nm.
vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv »

As of now I never managed to record a hologram from a FEG layer.
Meant to say at 532nm.
Same, tried with safranin-o dye added, no any results with green laser (even at tens times more exposition as my UV-near laser), plate is completely empty with no polymerization (all of gelatine washed off). Will try later when TEA will arrive, may be it'll help. But i guess, i need good blue laser just.
Do you happen to know the peak absorption wavelength of the Speedball diazo?
Nope. I found just some of unnamed diazo graphs on google with UV-near-blue peak.
vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv »

Finally got something that looks like hologram with 5mw 405nm laser at 300..480 seconds exposure with 2x3" slides (tried also 450nm laser but couldn't get anything useful yet, seems my adjustments for the laser wasn't enough). Got out of citric acid at previous failed runs (funny fact, it is hard to find it in the Dominicana somewhy), so this time was just 2g Ferric ammonium citrate (used less concetration to prevent blue shift) + 13g gelatine + 90ml water. Also added warm (45C) water bath and fixer bath (potassium aluminium sulfite) after developing in 1% of H2O2.

Interesting that slide lying in 99% IPA looks more colorful but when drying with hair dryer - it loses some of colored area and coins turn into weak white images of itself. Perhaps because high humidity here (90%+). Did help a bit when i did repeat 50+75+99 bathing and drying in my room with conditioneer at 50% humidity, loss of color is much less.
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Martin
Posts: 131
Joined: Sat Apr 04, 2015 2:36 am

Re: Ferric ammonium oxalate tests

Post by Martin »

vasimv wrote: Sun May 26, 2019 4:56 pm Finally got something that looks like hologram with 5mw 405nm laser at 300..480 seconds exposure with 2x3" slides (tried also 450nm laser but couldn't get anything useful yet, seems my adjustments for the laser wasn't enough). Got out of citric acid at previous failed runs (funny fact, it is hard to find it in the Dominicana somewhy), so this time was just 2g Ferric ammonium citrate (used less concetration to prevent blue shift) + 13g gelatine + 90ml water. Also added warm (45C) water bath and fixer bath (potassium aluminium sulfite) after developing in 1% of H2O2.

Interesting that slide lying in 99% IPA looks more colorful but when drying with hair dryer - it loses some of colored area and coins turn into weak white images of itself. Perhaps because high humidity here (90%+). Did help a bit when i did repeat 50+75+99 bathing and drying in my room with conditioneer at 50% humidity, loss of color is much less.
Congratulations! That looks very promising. The white color of the dry layer seems to indicate some layer damage. Maybe the water was simply too warm?

I'd skip the potassium aluminium sulfate step.
vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv »

Congratulations! That looks very promising. The white color of the dry layer seems to indicate some layer damage. Maybe the water was simply too warm?

I'd skip the potassium aluminium sulfate step.
Without fixer a lot of emulsion gets washed off in water. And wasn't able to get something near that without warm water. Whole thing is a bit complicated to me, looks like i have to get practiced with dichromated first.

Failed to get anything useful with my 405nm at bigger depth, must be really bad laser - only few millimeters deep and nothing visible after. And at small depths coins reflections get imprinted into the gelatine layer like photographs just. Going to raise power of my 450nm laser (can't be good too as it was 2.5w for engravers with bar-like beam and i just lowered its power output by decreasing current, but don't have anything else yet) with increased amount of FAC with mold coating, may be will able to get some transmission holograms at least.
vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv »

Didn't get any hologram with 4% FAC emulsion with my 405nm and 450nm lasers. Only semi-transparent reflections of coins in the gelatine, with white milky layer at lower exposures and transparent on higher. Not sure if that is right method, but i've examined plates with strong magnifying glass and found no any signs of diffraction patterns like i see on the hologram that i've posted (wave-like lines of different width all around). Only very small amount at edges on my transmission hologram attempt (nothing visible with any laser anyway). I think, high concetration raises sensitivity but lowers resolution, going to try 1% soon. Ordered some 50..150mw blue-ray laser diodes to find one that has good beam for small holograms.
vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv »

A bit confused. Couldn't get a reflective hologram but did copy a transmission one with 405nm laser (the master was made with red laser on litiholo film, i just placed the film on FAC emulsion plate under beam to get direct transmission copy). Perhaps i did something wrong as i see only small part of it at weird replay angle (with any laser) but did work still, it has original's depth and reflections from sides when i look from different angles. Not sure why i keep failing with reflective holograms, may be it is layer's thickness or my processing method.
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