Ferric ammonium oxalate tests

Dichromated Gelatin.
Martin
Posts: 84
Joined: Sat Apr 04, 2015 2:36 am

Re: Ferric ammonium oxalate tests

Post by Martin » Tue Jun 18, 2019 2:57 am

vasimv wrote:
Mon Jun 17, 2019 3:38 pm
With a way to do permanent large red-shift - FEG emulsion would perform much better (...).
Well, we definitely have the broadband option.

vasimv
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Re: Ferric ammonium oxalate tests

Post by vasimv » Tue Jun 18, 2019 7:06 am

Here's another, perhaps more promising article:
www.researchgate.net/publication/225168 ... holography
TEA+dye alone couldn't provide sensitivity, looks like the key is "N,N'-Methylenebisacrylamide". If i understood right, it adds more crosslinking(?) to the reaction with acrylamide (or glycerol in one of papers). Not cheap chemical but seems quite easy to get and low-toxic.

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

Re: Ferric ammonium oxalate tests

Post by Martin » Wed Jun 19, 2019 3:11 am

vasimv wrote:
Tue Jun 18, 2019 7:06 am
(...) looks like the key is "N,N'-Methylenebisacrylamide". If i understood right, it adds more crosslinking(?) to the reaction with acrylamide (or glycerol in one of papers).
Yes, MBA is to crosslink the Glycerol 1,3-diglycerolate diacrylate. As you can see by Jeff Blyth's presentation (https://av.tib.eu/media/21871), the system works nicely as long as the layer is kept wet.

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

Re: Ferric ammonium oxalate tests

Post by vasimv » Wed Jun 19, 2019 5:30 am

Yes, MBA is to crosslink the Glycerol 1,3-diglycerolate diacrylate. As you can see by Jeff Blyth's presentation (https://av.tib.eu/media/21871), the system works nicely as long as the layer is kept wet.
Ordered some MBA and acrylamide, couldn't find acrylic acid or diacrylate. :( Hope will able to go without or replace with something else. Tried adding safranin and TEA to speedball emulsion (no pure PVA yet), safranin did ok but after adding TEA - it got instantly polymerized into gum-like blob.

Adding FAC to TEA+safranin O emulsion didn't make consistent results, nothing holographic just coins reflections. Got weak ammonia smell during mixing, not sure if that was reaction FAC-TEA or bad pH adjusted TEA destroying gelatin. At 15 minutes exposure did look like 2..4 times better sensitivity to green (reflections are visible at whole beam area), but at 5 minutes - looks same (very weak reflection at most exposed spot). 45 minutes gave obvious overexposure (had only spot with reflection where emulsion was very thick). Tried to process one slide with 15 minutes exposure without H2O2 developer - nothing at all. My mistake was adding fixer bath, can't really compare results with pure TEA/dye emulsion. Had to add it because TEA emulsion was very weak, got heavy damage (peeled off, cracks) in good exposed areas.

Anyway, even if i got sensitivity boost from FAC - it is not great, beam strength was 50mw/12.5cm2 -> 4 mJ/cm2. So, still way over 3000 mj/cm2 to get anything.

Din
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Joined: Thu Mar 12, 2015 4:47 pm

Re: Ferric ammonium oxalate tests

Post by Din » Wed Jun 19, 2019 8:07 am

If you set up a Michelson, and put your plate with your emulsion into one path of the Michelson, ie between one mirror and the beamsplitter, then, as the material absorbed and cross linked, the density would change. As the density changed, the index would change. As the index changed, the phase of the light out of the plate would change, and the fringe system would shift. Can you not then determine sensitivity by marking the amount of shift of the fringe system as a function of time? It seems that determining the usefulness of this emulsion by exposing hologram brings other factors into play, and perhaps those other factors may be giving you this slow recording.

vasimv
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Re: Ferric ammonium oxalate tests

Post by vasimv » Wed Jun 19, 2019 11:00 am

If you set up a Michelson, and put your plate with your emulsion into one path of the Michelson, ie between one mirror and the beamsplitter, then, as the material absorbed and cross linked, the density would change. As the density changed, the index would change. As the index changed, the phase of the light out of the plate would change, and the fringe system would shift.
I know, my method sucks, but i haven't enough experience and much of stuff here. Not even beamsplitter (bought a semi-transparent mirror but it is on plexiglass and has visible texture in reflection). :( And if i understand correctly, crosslinking with ferric happens only in developer, so you can't determine FEG emulsion's sensitivity in real-time. i think it is could be possible to check Fe2+ content in emulsion by using infrared light as these ions block something about 1070nm light but will require precise equipment.

Btw, i've read something about self-developing ferric stuff somewhere (with a persulfate if i remember correctly) but the author did state it didn't work for the gelatin-based emulsions. :(

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

Re: Ferric ammonium oxalate tests

Post by Martin » Thu Jun 20, 2019 2:36 am

vasimv wrote:
Wed Jun 19, 2019 11:00 am
Btw, i've read something about self-developing ferric stuff somewhere (with a persulfate if i remember correctly) but the author did state it didn't work for the gelatin-based emulsions. :(
Ferric PVA has been used as a real-time recording medium (at 441nm). It used to be based on PVA + ferric chloride. No peroxide involved. Subsequent heat treatment was said to enhance DE. The system isn't quite high-speed though.

A Mexican group did some research on ferric systems (e.g. https://www.spiedigitallibrary.org/conf ... hort?SSO=1).

There's also been a acrylamide-MBA system with FAC and a peroxide incorporated.

Din
Posts: 224
Joined: Thu Mar 12, 2015 4:47 pm

Re: Ferric ammonium oxalate tests

Post by Din » Thu Jun 20, 2019 8:02 am

vasimv wrote:
Wed Jun 19, 2019 11:00 am
And if i understand correctly, crosslinking with ferric happens only in developer, so you can't determine FEG emulsion's sensitivity in real-time.
I don't know about Fe, but, in general, cross linking occurs at exposure. That's why you have an exposure time, to allow cross linking to take place. But, the cross linking is very weak. The initial cross linking is known as the Latent Image. The developing agent magnifies the amount of cross linking.

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

Re: Ferric ammonium oxalate tests

Post by vasimv » Sat Jun 22, 2019 8:08 pm

Finally received some 405nm laser diodes, two of them "NDV4313" (on beamq.com, not really this one as pinout doesn't match its datasheet) and SLD3236VF seems to have coherence length more than 6mm (did simple test with thick glass and this is thickest i have) but only at low power current (60mA, power output should somewhere at 5-20mw). Tried to use SLD3236VF to make holograms but failed on emulsion part - tried to dissolve gelatin in 0.5% solution of potassium alum, got gum-like substance and couldn't make good coating (tried to cover with piece of glass like butter on bread and failed to make uniform thickness). Although got small but very nice hologram spots with depth and colors (interesting, it gives more red-shift where coating has more thickness and goes to blue-shift at thinner areas). Will try to make more complicated process to get pre-hardened coating - coat with gelatin, then dry and dip first into potassium alum solution then into FAC solution. That should give strong coating, without unwanted reactions between components.

Also tried pure PVA with speedball diazo sensitizer, it does have sensitivity to 405nm (same or better than FAC, not sure yet) but no holograms. I do see coins reflections and rainbow around light source reflection from backside but this looks like just because kind of coating texture (possible because my bad coating method - just drying with hair dryer for few minutes and using plates right after). Coating have brown color (even after after-exposure water bath) and blocks much of light, looks like have to put less sensitizer. I've used 5ml of diluted sensitizer for 100ml of 5% PVA solution.

Joe Farina
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Re: Ferric ammonium oxalate tests

Post by Joe Farina » Sun Jun 23, 2019 6:44 am

For hardening gelatin, my preferred method is using chrome alum. I don't know if this is compatible with your ferric system, though. For example, one of my batches was mixed as follows: 0.5ml of a 5% chrome alum solution added to 47ml (room temperature) water, then 6 grams gelatin mixed into this and allowed to soak a while, then temperature raised to 44C. This works very well to reduce milkiness in my MBDCG. The chrome alum has dark purple crystals.

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