Ferric ammonium oxalate tests

[Martin]

Results are quite strange, i see bright colors are all over emulsion during 91% IPA bath (green and red mostly) and 99% IPA (shifting to blue) but after i try to dry slides with hair dryer - it turns to white mostly. I can repeat the process by dipping it into water and going through IPA baths again (31+75+91+99 at 29..30C) but after drying it gets just milky again.

The good news is the "bright colors" you observed.
Could it be your hologram of the dried layer has been shifted to the UV?
Have you ever tried putting your plates directly into the 99% IPA from your water bath?
If the water temperature comes close to the threshold temperature of your gelatin (28-30C with my gelatin), you should see very broadband reconstructions.

[vasimv]

Did second batch with same emulsion (dried without dryer at 28..30C 50..60% for 20 hours) and 28..30C H2O2, was able to keep some of colors (but still more of them in IPA). Warm water bath's temperature after developer don't mean much, tried any from 30 to 50C with slightly more light golden reflective colors at higher temperatures and blue/green at lower. Looks like pre-hardened emulsion with potassium alum is a bit easier to process, will try to play with different IPA baths for next batch. Looks like good idea to try warm H2O2 also, as with cold developer i haven't able to keep colors at all.

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Update: Tried to reprocess same plates with water -> 91 -> 99, blue shift is obviously less and colored areas got bigger (mostly blue still). But color contrast decreased, more milky. I guess, it because emulsion gets damaged from multiple reprocessing, so i'll try to dip in 90+ right after developing and washing next time.

[vasimv]

Got minor success with red shifting. Warm developer didn't help at all (but i've found that it is safe to increase developing time up to 3 minutes), tried citric acid and sugar (alone and in combination, in different concetrations) but only found the way to remove emulsion from used plates (citric acid does this good). Finally found that acetic acid (used diluted kitchen vinegar, definetely not pure acetic acid) doesn't peel off emulsion so hard as citric, in less than 2% concetration it is safe to keep plates in it for minutes.

So, my processing method was (29C, about 90% humidity):

1. 5..8 minutes exposure with 405 nm laser
2. H2O2 developer (3 minutes)
3. 1..2% acetic acid for 5 minutes (instead washing off in pure water)
4. 99% IPA (well, not really 99% as it is contaminated from my previous experiments already, will use new one next time).
5. Drying with hair dryer in 50% humidity environment

It still gets blue (into UV) shifted but less than day ago. Also, it is clearly that most of shift is going on corners, possible affected by emulsion thickness (simple veil coated, 20 hours drying) or not good stirring during processing.

Also, i was able to get more red shift by re-processing with water->33->75->91->99 (last photo), lost some saturation and sligthly more milky.

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[Martin]

That looks pretty holographic already!

[vasimv]

That looks pretty holographic already!

Well, acetic acid's effect wasn't permanent. They slowly shifted to blue/UV again in day, even sealed one. Either i didn't good drying or this was just short effect. Will try to shoot holograms in 60% humidity with more exposure, may be this will cause less blue shift.

As part of my alchemy program, tried TEA+Safranin O emulsion and 50mw green laser with developing in FAC+H2O2 solution. Wasn't going to work and it didn't, emulsion got wiped off just. Will try to add FAC in emulsion directly to test but low chances as i understand.

Pure TEA+Safranin O has low sensitivity to green and i did get small area (1 cm2 about) with true hologram, depth and resolution were amazing - not just surface color with barely visible depth as in my FAC attempts. But it did require something like thousands MJ/cm2 (90 minutes with 50mw laser circle with 1.5 inches diameter), not really useful. Tends to have blue shift also (humidity again?). Found article about successful holography with PVA+TEA+MB+some stuff, going to try simplified version of that with safranin too as soon as PVA shipment arrives: http://sutlib2.sut.ac.th/sut_contents/H ... 636_84.PDF

[Joe Farina]

For DCG, I have red-shifted (to an extent) by incorporating collagen into the emulsion during the processing stage. This is the type of collagen I used: https://www.amazon.com/Great-Lakes-Gela ... M0K64&th=1

It's soluble in cold water. From what I gather, the collagen gets into the matrix of the emulsion, and causes it to shrink less. This is done towards the end of the processing. Stojanoff wrote papers concerning this, such as: https://www.researchgate.net/publicatio ... _no_613601

Might be worth looking into.

[vasimv]

For DCG, I have red-shifted (to an extent) by incorporating collagen into the emulsion during the processing stage. This is the type of collagen I used: https://www.amazon.com/Great-Lakes-Gela ... M0K64&th=1

It's soluble in cold water. From what I gather, the collagen gets into the matrix of the emulsion, and causes it to shrink less. This is done towards the end of the processing. Stojanoff wrote papers concerning this, such as: https://www.researchgate.net/publicatio ... _no_613601

Ah, thank you, good night bed reading. With a way to do permanent large red-shift - FEG emulsion would perform much better as we don't have way to shift its sensitivity to green and only 405nm looks like suitable option (445/450nm works in high humidity environment but still not good as 405). Few types of 405nm laser diodes on way to me, hope i'll have one with more than 3mm coherence length.

[Joe Farina]

You're welcome. If you decide to try red-shifting with hydrolyzed collagen, this is an example of what I did with MBDCG:
After exposure, emulsion soaked in water to swell, then soaked in a 6% solution of hydrolyzed collagen (in water) for 30 minutes, then dehydrated in alcohols. This resulted in a noticeable red-shift, with no decrease in brightness. The only problem (which I haven't worked on yet) is the uniform removal of the collagen solution, after the 30 minute soak. It might be possible to use a Mayer bar (or some other method like spinning) to remove the 6% collagen solution uniformly from the surface of the layer. (Longer soak times might produce more of a red-shift, I haven't tried it yet).

[Martin]

Found article about successful holography with PVA+TEA+MB+some stuff, going to try simplified version of that with safranin too as soon as PVA shipment arrives: http://sutlib2.sut.ac.th/sut_contents/H ... 636_84.PDF

Here's another, perhaps more promising article:
www.researchgate.net/publication/225168 ... holography

[Martin]

For DCG, I have red-shifted (to an extent) by incorporating collagen into the emulsion during the processing stage.

Good point, thanks for reminding us. I had forgotten about the collagen.