Ferric ammonium oxalate tests

Dichromated Gelatin.
dannybee
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Ferric ammonium oxalate tests

Post by dannybee »

Martin wrote:
dannybee wrote:ooo Iron-silver this might be interesting using the hardning of the Ammonium Ferric Citrate, and the senitvity of Silver :D

The Process
Sensitiser

note: rinse all utensils in distilled water before use.
Make 3 separate solutions;

6g Ammonium Ferric Citrate in 22ml distilled water
1g Tartaric Acid in 22ml distilled water
2.50g Silver Nitrate in 22ml distilled water
I tried that one. At 405nm that mixture didn't produce anything holographic. Speed was low. I believe the material doesn't provide the necessary resolution. Note by the way, that these ferric/silver nitrate mixtures are supposed to produce metal (= "black") silver. So similar to AgX, you'd have to bleach the layer subsequently.
hears my thought I think in this normal mix the grain is way to large
but if we handle it like Hans DYI Process we can get the grain small (just like in silver)

process Idea
1 Silver Nitrate in the gel coated onto glass
2 30 sec in bath of Ammonium Ferric Citrate
3 Rince in di water then let dry
my thougth here is the Ferric will harden the gel with the speed of silver (Ferric/Sliver) also dyes can be added as needed
with a bleach and fixer it can be processed like a DCG .....its a idea :D
Martin

Ferric ammonium oxalate tests

Post by Martin »

dannybee wrote:process Idea
1 Silver Nitrate in the gel coated onto glass
The silver nitrate may react with the gelatin meanwhile. Or, if its concentration is too high, it will precipitate out on top of the layer...
2 30 sec in bath of Ammonium Ferric Citrate

I'd fear that in that bath you'll simply wash out the silver nitrate from the layer. No "grains" à la AgX will form...
3 Rince in di water then let dry
my thougth here is the Ferric will harden the gel with the speed of silver (Ferric/Sliver) also dyes can be added as needed
The hardening doesn't come from the FAO (or FAC etc.) alone. Actually, very little "dark reaction" seems to be taking place. That's why gelatin/FAO solution have very good keeping properties.
For hardening you need both the action of light and peroxide. Incidentally, I still believe in the FEG process (and perhaps this is true for DCG as well) you actually get both hardening and softening effects within the layer.
also dyes can be added as needed
I don't know if you'd end up with any kind of spectral sensitization. Moreover, at 405nm FEG proved to be far more light sensitive than the Van Dyke mixture.
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jsfisher
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Ferric ammonium oxalate tests

Post by jsfisher »

A good thread should never die, and this thread is no exception.

Have there been any follow-up developments with ferric ammonium oxalate and gelatin? Those of us without suitable blue lasers are anxious to hear more. I would think some of the same dyes used to sensitize dichromates would be of some use with FAO.
World's worst holographer
Dinesh

Ferric ammonium oxalate tests

Post by Dinesh »

Martin wrote:That's why gelatin/FAO solution have very good keeping properties.
Well,I note that I shot the holo in January of 2012. The hologram was never sealed, yet it never faded, as all dcg's do. We've had pretty high humidity at times, but the hologram was still there. Finally, about a couple of months ago, I simply threw the holo into the reject pile for eventual re-cycling. So, it may be buried under a pile of old holos or it may already be recycled.

We've been busy with students these past few weeks, so we've had no time for any practical experimentation (I've played around with a few theoretical ideas, but I'm pretty sure no one here is interested in those. I've also been working on replacing some of our systems with an Arduino/Raspberry Pi and been doing quite a bit of X Window programming on Linux). However, we do have some down-time now, so if there's any interest, I can coat a few more plates and try an H1/H2 setup. I note that it took a lot of exposure to make the Denisyuk, maybe the H1/H2 setup will require less energy.
Martin

Ferric ammonium oxalate tests

Post by Martin »

jsfisher wrote:Have there been any follow-up developments with ferric ammonium oxalate and gelatin?
From time to time I get back to FEG, trying a few new things. What has become clear now is that control of the layer thickness is key. If the coatings are too thick, processing yields opaque layers only. If they're too thin, processing leads to loss of material - again no hologram will show up. By the way, layer thickness of the successful holograms seems to be around 10um.
It looks like that the ferric/peroxide systems have to be well balanced in regard to the H2O2 diffusion into the layer. Obviously, thick layers somehow prevent gelatin crosslinking. Maybe after laser exposure the freshly formed Fe2 (ferrous) parts get washed out before they can react with the peroxide to interact on the gelatin strands (at the light fringes).
Those of us without suitable blue lasers are anxious to hear more.
Well, speaking of suitable lasers, that's just another "variable" making my FEG tests very unpredictable. Beyond some guessing about mode hops it's hard to figure out the behavior of the violet diode I use.
I would think some of the same dyes used to sensitize dichromates would be of some use with FAO.
Absolutely, you're right, it's definitely possible to spectrally sensitize FEG. For red sensitized layers I occasionally got very good diffraction efficiency. But limited spatial response remains a huge issue. So as of now I've yet to record a reflection holograms.
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jsfisher
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Ferric ammonium oxalate tests

Post by jsfisher »

Martin wrote:
jsfisher wrote:Have there been any follow-up developments with ferric ammonium oxalate and gelatin?
From time to time I get back to FEG, trying a few new things. What has become clear now is that control of the layer thickness is key. If the coatings are too thick, processing yields opaque layers only. If they're too thin, processing leads to loss of material - again no hologram will show up. By the way, layer thickness of the successful holograms seems to be around 10um.
Would thickness be less of an issue if you used a dip method? (I.e., coat plates with gelatin only, dry, then later dip in an FAO solution.) I'd think control of dip time would regulate how deep the FAO penetrated the gelatin.
...
I would think some of the same dyes used to sensitize dichromates would be of some use with FAO.
Absolutely, you're right, it's definitely possible to spectrally sensitize FEG. For red sensitized layers I occasionally got very good diffraction efficiency. But limited spatial response remains a huge issue. So as of now I've yet to record a reflection holograms.
Unfortunately, the dye chemicals tend not to be readily available to the rank amateurs such as myself. I've wondered, though, if something as simple as red food coloring could serve as a make-shift sensitizer for green. (In the US, red is a mixture of red dye #40 and #3, the latter being Erthrosine. I have no idea of the ratios, though.)
World's worst holographer
Martin

Ferric ammonium oxalate tests

Post by Martin »

jsfisher wrote:Would thickness be less of an issue if you used a dip method? (I.e., coat plates with gelatin only, dry, then later dip in an FAO solution.) I'd think control of dip time would regulate how deep the FAO penetrated the gelatin.
Putting FAO, FAC etc. into the gelatin prior to the laser exposure is easy. And getting the peroxide into the layer (during development) isn't difficult either. The problem as I see it is to balance the two diffusion processes taking place during development:

1) The H2O2 entering the layer to react with the freshly generated Fe2 (by the laser exposure that is) at the bright fringes only. No hologram forms when the Fe2 and the H2O2 are reacting outside that area. The reaction of the H2O2 with the Fe2 is called FENTON reaction. It's unclear what's taking place exactly within the gelatin matrix. It seems to me that both crosslinking and "softening" may occur at the same time.

2) The washing off/removal of the remaining iron salts.
Unfortunately, the dye chemicals tend not to be readily available to the rank amateurs such as myself. I've wondered, though, if something as simple as red food coloring could serve as a make-shift sensitizer for green. (In the US, red is a mixture of red dye #40 and #3, the latter being Erthrosine. I have no idea of the ratios, though.)

Yes, that's the kind of dyes you'd have to look for (not the cyanine dyes used for AgX sensitization).
I assume many useful dyes are available from companies dealing with stains for microscopy (https://en.wikipedia.org/wiki/Staining).
vasimv
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Re: Ferric ammonium oxalate tests

Post by vasimv »

Found interesting article: https://www.jstage.jst.go.jp/article/ph ... f/-char/en

According to it, adding citric acid does help to improve sensitivity almost to dichromated gelatin level. Not sure if it will work for holography, going to try this (as my shippment of dichromate is delayed yet).

Also, there is interesting idea to cover FEG emulsion with protective cover of agar agar to block oxygen-ferric reaction (while H2O2 can go through it still. Wonder, why don't try to make pure ferric-agar emulsion, without gelatin at all.
Martin
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Re: Ferric ammonium oxalate tests

Post by Martin »

vasimv wrote: Thu May 16, 2019 8:56 pm Found interesting article: https://www.jstage.jst.go.jp/article/ph ... f/-char/en
It very much looks like a short version of the CHIBA system paper (www.polychrome.nl/file_download/4/TheChibaSystem-HR.pdf).

I still think ferric gelatin (FEG) has nothing to do with free-radical POLYMERIZATION - as long as no monomer has been added.
In a FEG system the free radicals generated (by the reaction of the H2O2 with Fe2+) may actually attack and disrupt parts of the gelatin. So the whole process seems to have more to do with PHOTODEGRADATION than polymerization.That said, there could still be gelatin crosslinking from Fe3+ (particularly when ferric chloride is present).

In my crude view of the mechanisms involved with FEG, things approximately look like this: on the light fringes ferric (Fe3+) is reduced to ferrous (Fe2+). On contact with the H2O2 hydroxyl radicals are formed, which then attack the gelatin in that area. Maybe part of the Fe2+ is re-oxidized by the H2O2, leading to some slight crosslinking. In any case the crosslinking doesn't come anywhere close to Cr3+ crosslinking in a DCG system. That can also be concluded from the fact that re-processing of FEG layers cannot be done numerous times.

According to it, adding citric acid does help to improve sensitivity almost to dichromated gelatin level. Not sure if it will work for holography, going to try this (as my shippment of dichromate is delayed yet).
I'm looking forward to learn about your tests.
In my experience adding citric (or tartaric, oxalic, lactic) acid didn't enhance speed.
By the way, at 405nm speed of FEG may be at least on par with DCG. But it also depends on the particular gelatin.
I think the whole discussion about which ferric ingredient has better speed, FAO or FAC essentially depends on their absorption wavelight.
Most photo people making Cyanotypes use either UV or sunlight. I guess FAO has a higher light absorption at 365nm than FAC.
Also, there is interesting idea to cover FEG emulsion with protective cover of agar agar to block oxygen-ferric reaction (while H2O2 can go through it still. Wonder, why don't try to make pure ferric-agar emulsion, without gelatin at all.
It's difficult to make agar stick to glass. As for its oxygen barrier qualities there are probably better options out there.
Grayham
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Re: Ferric ammonium oxalate tests

Post by Grayham »

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?

I know it's not the same thing but in the same vein.

Grayham
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