Ferric ammonium oxalate tests

[Dinesh]

Martin
I've coated 10 plates with your FAO formula and I'm going to shoot them with 457 on Thursday (Jan 5th). Any idea of exposure?

[Martin]

Martin
I've coated 10 plates with your FAO formula and I'm going to shoot them with 457 on Thursday (Jan 5th). Any idea of exposure?

Wow, great news!
How do your plates look against a 457nm lit background? Do you notice any light absorption?
If so, I'd start with say, 1 - 4x the DCG exposure level.
By the way, new recording materials may sometimes behave rather unexpectedly, so I'd add a transmission holo element to your recording scheme (since a transmission grating is much easier to detect). E.g. I often put a transmission grating on top of the recording plate/film placed on a standard coin object.

[Dinesh]

Here's the first set of tests. Plates were made as follows:
30 gms 250 bloom pork gelatin
6 gms FAO
300 mls water

Plates were coated on Monday 2nd Jan. and exposed today (5th Jan). I did not measure the thickness, but I would approximate about 7 to 9 microns. Geometry was a two-beam transmission grating at zero degrees and 24 degrees (~900 l/mm) at 457 nm from a solid state Melles Griot laser. I started the first exposure at 50 mJ, then increased by 10 mJ until finally the last shot was at 120 mJ. Below is a picture of the 60 mJ exposure (the second exposure).

Processing was as follows:
10 seconds in 1% Hydrogen Peroxide
2min water @ ~ 18 deg C
dehydration with IPA as per dcg

The 50 mJ exposure was very, very weak. It could only be seen under direct sunlight. I would judge less than 5%. By about 80 mJ, the hologram was viewable with a halogen lamp and I would judge about 10%, The last one, at 120mJ was bright enough to be clearly and easily seen under fluorescent lighting and would make a good H2 on dcg. I would judge about 25%. This kind of exposure is about, maybe, 3x dcg exposures.

Tomorrow (6th Jan), I'm going to start at 120mJ and try to make a single beam Denisyuk. Will post pictures and results if succesful.

[Martin]

Processing was as follows:
10 seconds in 1% Hydrogen Peroxide
2min water @ ~ 18 deg C
dehydration with IPA as per dcg

The 50 mJ exposure was very, very weak. It could only be seen under direct sunlight. I would judge less than 5%. By about 80 mJ, the hologram was viewable with a halogen lamp and I would judge about 10%, The last one, at 120mJ was bright enough to be clearly and easily seen under fluorescent lighting and would make a good H2 on dcg. I would judge about 25%. This kind of exposure is about, maybe, 3x dcg exposures.

That doesn't sound that bad. Glad to learn you were able to record holograms. I had feared my culinary gelatin was somewhat too "special".
Speaking of gelatin, with the stuff I use, index modulation clearly is related to the the temperature of the water bath. Depending on the degree of crosslinking, best results used to be achieved at ~30°C. But I don't know if your gelatin will behave in the same way.

[dannybee]

this sound so familiar .. like a old photo process http://en.wikipedia.org/wiki/Cyanotype
http://photochemistry.epfl.ch/PC/PC2_Lesson_9.pdf
http://www.google.com/#hl=en&sa=X&ei=LS ... 09&bih=916

[Dinesh]

Danny, thanks for bringing this to our attention. There may be a lot of old photographic processes that could be adapted for holography, but the question remains, can these photographic processes take the spatial frequency requirements of a hologram. Typically, a photographic process needs roughly 200 l/mm, while a hologram needs 10 times this and more.

I do think we need to look into alternate materials that can reproduce dcg-type holograms because dichromate is rapidly being banned world wide. I understand that it's very difficult to get it in Europe and in the US, I need to sign a document stating why I want to buy the stuff, a requirement that never existed before. The word among the wise is that we have maybe a year or two before dichromate is on the banned list here also.

However, in order to get a new material with dcg-type characteristics up and ready in a couple of years, we need to thoroughly determine the parameters: how high a spatial frequency can be recorded? What is the exposure curve? What is the max index modulation? etc etc. Unfortunately these old photosensitive materials don't answer any of these questions and these questions can only be answered by repeated testing.

[dannybee]

I do think we need to look into alternate materials that can reproduce dcg-type holograms because dichromate is rapidly being banned world wide. I understand that it's very difficult to get it in Europe and in the US, I need to sign a document stating why I want to buy the stuff, a requirement that never existed before. The word among the wise is that we have maybe a year or two before dichromate is on the banned list here also.

I have no problem getting it , I get mine from ebay, no docs to sign http://www.ebay.com/sch/i.html?_from=R4 ... Categories

[Martin]

this sound so familiar .. like a old photo process http://en.wikipedia.org/wiki/Cyanotype
http://photochemistry.epfl.ch/PC/PC2_Lesson_9.pdf
http://www.google.com/#hl=en&sa=X&ei=LS ... 09&bih=916

Yes, FEG undoubtedly relies on Herschel's cyanotype process to the extent that it makes use of light-sensitive ferric salts. But that's about it. There is no "cyan" (no ferricyanide) component involved.

Cyanoacrylates (which are the chief agents of instant adhesives, Super Glue and alike) have nothing to do with cyanotypes or FEG.

[dannybee]

this sound so familiar .. like a old photo process http://en.wikipedia.org/wiki/Cyanotype
http://photochemistry.epfl.ch/PC/PC2_Lesson_9.pdf
http://www.google.com/#hl=en&sa=X&ei=LS ... 09&bih=916

Yes, FEG undoubtedly relies on Herschel's cyanotype process to the extent that it makes use of light-sensitive ferric salts. But that's about it. There is no "cyan" (no ferricyanide) component involved.

Cyanoacrylates (which are the chief agents of instant adhesives, Super Glue and alike) have nothing to do with cyanotypes or FEG.

whats the formula ???? share

[Martin]

whats the formula ???? share

What formula? Regarding ferric gelatin (FEG) everything is here on the forum. As for cyanacrylates, I only know them from using super glue...