Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Silverhalide Emulsions / Chemistry.
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thycore
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by thycore »

Hey folks, I just have kind of a doubt here about this film sensitivity.
My laser is an Helium-Neon (meaning somewhat 632nm). I read somewhere in the previous posts that the Holofilm 250 par was used in combination with a pulsed ruby laser. These kind of lasers are rather deep red, like 694nm, aren't they ?

Are there reasonable reasons to believe my exposure will suffer from this ? or luckily enough the red dye in the film is broadly sensitive to all red spectrum ?
Ed Wesly
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by Ed Wesly »

I did use it with a He-Ne, shooting some transmission holograms. I developed it with an Ilford liquid concentrate, Phenisol, which is their version of Kodak D-19. So I don't think you should have any problems.
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thycore
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by thycore »

Thanks !

I would be a nice idea to open a new page on the holowiki's wiki pages with a matrix showing possible combinations between known plates/films and known developers/bleaches from the market and if these recipes are known (meaning available on holowiki) :
matrix.jpg
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thycore
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by thycore »

Hi !

I made my first attempt tonight with these Holofilm.

I exposed 10 seconds a piece of 24cm x 24cm sandwiched between 2 pieces of glass. (I left my set-up at rest for 20 minutes before exposure to settle it down).

After the first D-19 revealer bath I was clearly able to see the hologram (interference pattern in brown colour) which is usually a good indicator of the success of your shooting.

But then I bleached approx 20 seconds in EDTA Bleach and it somehow went wrong ! I have a substantial amount of white/cream precipitate which shown up and deposited on my film (when dryied it look like salt or fine grain of sand).

I used this formula :

Ewesly / Holographic Formulae / Benign Ferric EDTA :
Revised formula
30 g Ferric Sodium-EDTA
30 g Potassium Bromide
30 g Sodium Bisulfate
One litre water

I suspect 3 phenomena :

- too long bleach bath which could have "eaten the gelatine" ?
- not clean enough trail which may contain previous chemicals or tap water's salts ? (quite doubtly... but why not ?)
- not adapted formula to holofilm ?

Any idea? :)
Ed Wesly
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by Ed Wesly »

I didn't have any luck with that Fe EDTA bleach either. See one of my earlier posts above, June 16th, where I cut a piece in half and bleached one side with Benign and the other with 'Chrome. And the other rehalogenating bleach I tried was even more pitiful so I didn't even post pictures. For some reason the film doesn't take to that type of processing.

So my suggestion is to get some potassium dichromate to make the 'Chrome bleach. A most reliable source in the US, (where do you live?) is Photographers' Formulary for small amounts of stuff. In other parts of the world you should be able to find it from sources who deal in alternative photographic processes, as it is the light sensitive substance in a 19th century process, still popular, called gum bichromate.

And you don't need the sulfuric acid, as I mentioned above, but sodium bisulfate, available at pool and spa suppliers, or from the Formulary. Use 3 grams (2.82g to be exact) of the powder for every mL of sulfuric acid. Sulfuric acid used to be known as "battery acid", so you might try that route.

You don't necessarily need to bleach to get a result. You could leave the hologram black with silver, and you could fix it with the typical photo darkroom chemical but that's not really necessary. And you don't have to develop as dark as when you bleach, cutting down exposure time. The image will not be as bright as a bleached one, but at least you get to see something. And the signal to noise (contrast, or how black are the shadows) will be better!

How dark do you need it to get? Run a test strip as described here:http://edweslystudio.com/Pedagogy/TS/Te ... meset.html

It sounds like you are moving forward! But this is how things go in this field.
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thycore
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by thycore »

Right ! seems I came to the same result as yours :) this was the picture of your test (back from 16 june post) :

Image

And this is a close view on my bleached & 1 night dried film :
IMG_3205.JPG
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When i emptied my trail back to the bottle, I can cleary see the "deposit" on the bottom of the bottle (I suspect this power-stuff being the same as the one scattered on the film after bleach bath), I wonder if this is "chelated Ag+ stuff" or if this is some other sort of chemical ?
IMG_3206.JPG
IMG_3206.JPG (442.58 KiB) Viewed 13988 times
I ordered some Potassium Dichromate (and a gaz mask to handle it safely.. xD) and i'll give it a try !
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thycore
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by thycore »

I made a test "without" bleaching, I can clearly see the fringes of my hologram in the center (my microscope lens does not expand my beam much bigger than 10cm diameter, that's why only the center of this 25cm wide film part is dark).
IMG_3207.JPG
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I developed for approx 4 minutes, then I rinced in distilled water for 4 minutes.

The film somwhat quickly turned from transparent to amber-colored like. Is this a sign of under-development ?
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thycore
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by thycore »

I made a new test again, this time I developed in D-19 for nearly 6 minutes.

This time, the film around the exposed area remains transparent :
IMG_3208.JPG
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But, somehow, I see nothing as a hologram (no shiny red/green whatsoever)... the interference pattern shows nicely and with good contrast but nothing pops out, is this possible to have a good inteference pattern but no hologram ? or do I *have* to bleach it to see the hologram ?.
jeff-blyth
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by jeff-blyth »

Hi Thycore,
From what you say about seeing interference (colours )but no red image, ---this indicates I think that you have smudged your reflection fringes due to a tiny movement perpendicular to the plane of the film. Such movements do not do much damage to spurious transmission gratings whose fringes are also perpendicular to the film .(These are created by a spurious reflection from the film /air interface sending back a spurious beam from the same side as your object). I strongly recommend making your film tests initially on simple bright coins by working horizontally and beaming up from underneath as per my posting of 18th February 2017 in the "beginning holography" thread.
Ed Wesly
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Re: Which chemistry for "HOLOFILM 250 PAR" from Applied Holographics PLC ?

Post by Ed Wesly »

I have posted a bunch of brochures and pamphlets and leaflets pertinent to this discussion at: http://edweslystudio.com/Materials/AgX/AgXindex.html

Have fun!
"We're the flowers in the dustbin" Sex Pistols
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