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[quote="Joe Farina" post_id=72860 time=1687808431 user_id=2184]
Martin, you've almost certainly seen this old 1978 report, but in case you haven't, it includes some info on diazo sensitization:

https://erdc-library.erdc.dren.mil/jspui/bitstream/11681/11334/1/ETL-0128.pdf

Also some mention of casein, and among other things, corn zein :)
[/quote]

Yes, thanks, I've seen it.

In the 1980 paper I had mentioned earlier in this thread (Gladden, Grating formation in diazo salt (sensitized) gelatin) Gladden seems to have based his diazo gelatin tests but on fixed Kodak 649F plates. That produced some rather modest results in respect to DE, speed. I assume using a fixed AgX gelatin layer was kind of suboptimal. Who knows how the history of DCG (and diazo gelatin) had turned out if Gladden had coated his plates on his own.

Martin, you've almost certainly seen this old 1978 report, but in case you haven't, it includes some info on diazo sensitization:

https://erdc-library.erdc.dren.mil/jspui/bitstream/11681/11334/1/ETL-0128.pdf

Also some mention of casein, and among other things, corn zein :)

[quote=Din post_id=72851 time=1687718547 user_id=2357]
Here's the contents page for DCG and other materials. I used the method of carbon printing (chap 2.1b) to show it was possible to use DCG as a resist material. We recorded a thin hologram on DCG with depth < 1u, and then transferred the image to a piece of plastic by casting. We poured Norland onto the DCG, and laid a plastic film on the Norland. After curing the Norland, we peeled it off and showed the image on the plastic film. Processing was simply a warm water bath.
contents.jpg
[/quote]

Amazing! Using it as a resist seem to be the classic approach to DCG. By the way, I am pretty sure the ferric or diazo gelatin systems could be used for this as well.

In the context of DCG I always wandered how Curran/Shanoff got to the alcohol dehydration thing. I never found anything alike mentioned before in the photographic litterature.

[quote=Din post_id=72850 time=1687717972 user_id=2357]
[quote=Martin post_id=72807 time=1683365680 user_id=2364]
[quote=Din post_id=72801 time=1683214853 user_id=2357]
Joy tells me that I tried to throw it out when we left Triple Take behind, but she rescued it; she knows it's somewhere, but doesn't know where. [/quote]

That sounds exciting. Would be nice to see it online some day.

[/quote]
Martin, Joy found the book I inherited from Don Broadbent.
non-silver.jpg
[/quote]


I see, thanks for mentioning!

Jaromir Kosar's Light-Sensitive Systems: Chemistry and Application of Nonsilver Halide Photographic Processes still is an extremely important book I think. Jeff sent me a copy of that book in the early 2000s. Ever since I've come back to it time and again. It covers an incredibly large area of topics.

Here's the contents page for DCG and other materials. I used the method of carbon printing (chap 2.1b) to show it was possible to use DCG as a resist material. We recorded a thin hologram on DCG with depth < 1u, and then transferred the image to a piece of plastic by casting. We poured Norland onto the DCG, and laid a plastic film on the Norland. After curing the Norland, we peeled it off and showed the image on the plastic film. Processing was simply a warm water bath.
[attachment=0]contents.jpg[/attachment]

[quote=Martin post_id=72807 time=1683365680 user_id=2364]
[quote=Din post_id=72801 time=1683214853 user_id=2357]
Joy tells me that I tried to throw it out when we left Triple Take behind, but she rescued it; she knows it's somewhere, but doesn't know where. [/quote]

That sounds exciting. Would be nice to see it online some day.

[/quote]
Martin, Joy found the book I inherited from Don Broadbent.
[attachment=0]non-silver.jpg[/attachment]

[quote=Din post_id=72803 time=1683307156 user_id=2357]
The first thing that occurred to me was the size of the reproduction source. But, you say you can get sharp holograms with silver, so this does not appear to be the problem. Joy asked if you used the same source, at the same distance, for the sharp hologram as the blurred ones.
[/quote]

I forgot to reply to Joy's question. Yes, with the same source and distance, although I haven't done silver since the 90's. But I've noticed, especially with Agfa, that clear and sharp images are typical, with excellent sharpness and clarity in the deeper parts of the image. This is often not the case with DCG. I have a feeling this is partly due to the narrowband nature of silver. Of course, DCG can be made narrowband, low-noise, and sharp in the deeper parts (although this latter quality is something I rarely see). Agfa will probably have strict protocols and quality control measures, unlike many (non or semi-professional) display DCG makers. So, all of the factors you mentioned earlier about possible sources of scatter, noise, etc., are something the professional (HOE maker) like yourself would be aware of, and be able to deal with. For DCG, the burden of producing a quality, low-noise product would rest on the shoulders of the maker. The home-DCG'er is probably not aware of possible noise sources, or even willing to go through the extra trouble to correct the problems. Most of the time, the objective seems to be in making extremely bright (i.e., broadband) holograms, without a great deal of concern about noise.

[quote=Din post_id=72801 time=1683214853 user_id=2357]
Joy tells me that I tried to throw it out when we left Triple Take behind, but she rescued it; she knows it's somewhere, but doesn't know where. [/quote]

That sounds exciting. Would be nice to see it online some day.

I've been reading a great many papers on AgX, DCG etc. For AgX the specific impact from gelatin (and, later from the addition of sulfur and reduction sensitizers) has been established pretty clearly. I don't see anything alike for DCG. Sometime around the 1990 scientific papers on DCG seemed to have switched from dichromated gelatin to dichromated polyvinyl alcohol. It was pointed out that the less complex chemical structure of polyvinyl alcohol provided better insight into the mechanisms of light-sensitive dichromated systems. But in hindsight it looks a bit like capitulation.

I guess what I've been missing was something similar to what happened to silver halide photography: once the sensitivity promoting gelatin components were identified, they were added to highly purified ("inert") gelatin subsequently. Something alike I naively expected to find for DCG (let alone FEG or diazo gelatin). That would have culminated in adding the chemical(s) XY to some inert gelatin in order to get increased speed/modulation. Various speed enhancing chemicals have been mentioned earlier but to the best of my knowledge there has never been systematic research in that area.

Thanks very much Din. Please thank Joy also.

After a 6 year hiatus from DCG, I'm having to re-learn many things. I will be carefully re-reading your posts, and also searching the forum for old posts. There is truly a wealth of information here, if one is willing to search. Regarding scattering in the emulsion, I've made numerous sins lately, including not filtering the emulsion. Another potential error was only heating the emulsion to about 40C (just above the melting temp). If I go higher, say to 50C as you mentioned, I have a feeling the emulsion will be more homogenous. The many potential sources of scattering need to be considered, I think, as you outlined so well in this thread. I also found an old post of yours at:

https://holographyforum.org/forum/viewtopic.php?f=7&t=847&hilit=%26amp%3Bamp%3Bamp%3Bamp%3Bamp%3Bquot%3Btype+A%26amp%3Bamp%3Bamp%3Bamp%3Bamp%3Bquot%3B+gelatin

Today, I bought some silicone molds which I think can be used to make small cubes of gelatin/dichromate. Then I can send a laser beam through the cube, and observe scattering on the sides. This may help considerably with the choice of gelatin, etc. My current DCG formula has a lot in it: gelatin, potassium chromate, TMG, acetic acid, methylene blue, rhodamine 6G, and chrome alum (the latter I've found helpful for bias hardening). All this stuff could contribute to scattering. The cube test may help with this also.

My current plan is to go back to basics for a while, and temporarily forget about color. I just want to do regular DCG (gelatin/dichromate/488nm) and then start to think about color. The most important thing to me is the strength of the image, its clarity, the clarity being maintained over a reasonable depth, say 2.5 inches, and being narrowband overall. Brightness needs to be at a certain level, but it's not the overriding factor to me.

Thanks for the photo, I appreciate it. I've taken a photo of a very poor hologram I made this week (of some painted marbles). There was no attempt at balancing the power of the lasers, the 488nm was turned all the way up to 200mW (much higher than 532nm and 633nm), so the image is quite blue overall. I've gotten so out of practice that I still can't identify the reason for the miserable horizontal splash marks.[attachment=0]P1010054.JPG[/attachment]

[quote="Joe Farina" post_id=72802 time=1683220284 user_id=2184]
Also, can a DCG hologram be made narrowband enough to produce a very sharp image with say three inches of depth, comparable to what silver halide can do?

Thanks.
[/quote]

Yes, this one is about 4 inches deep.
[attachment=0]plane30152.jpg[/attachment]