Rejuvenating old Ilford plates

Holography related topics.
dannybee
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Re: Rejuvenating old Ilford plates

Post by dannybee »

I think its got to be simpler than that :D , 1 if you take the plate out to the sun will it expose? if it does, does it expose to uv or blue? if it does, then maybe just maybe the dye in the plate is no longer working, the question is can the bleach alter the ph of the dye or even alter it.. or can age alter the dye... simple test expose 1/2 plate to laser light and 1/2 to sun..... then if this is the case the dye was altered .. you can reintroduce the dye... also not sure if when you use ferric EDTA bleach to convert the silver specks on the silver crystal whether if its got a lot of specks (way over fogged) (I think I remember it needs at lest 3 specks which is what you do with ascorbic acid bath) if this will make the size of the crystal bigger there by changing the dynamics of the film or plate(just a thought here) I've used this even on fogged litho film and it works great...EDTA bleach is great
walschuler
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Re: Rejuvenating old Ilford plates

Post by walschuler »

A progress note:
After consulting with the Olsens, who donated the plates long ago, I tried a 5 minute water pre-soak. We got images (THANK YOU R and B!), albeit not very strong ones. The OD was 1.5 and 2.0 in the trials, and the images about the same strength in them. This OD for that exposure is consistent with my memory of the last prior student experience, several years ago. We tried post-devo ferric EDTA bleach and then ascorbic acid redevelopment, standard with PFG-01 in class, and neither improved the image, in fact they weakened it. This is also consistent with memory of the performance of Ilford plates.

So several questions: Why did the water pre-soak work?
An older question: why does water presoak hypersensitize emulsions by a factor of about two? Why does TEA do that too?
Danny and Dinesh offered suggestions involving dyes and emulsion cracking which I have not yet tested, but they are on my list....
Why should Jeff's suggestions about pre-exposure dilute bleach and devo have worked and why didn't they??
I can get along empirically but really like to be able to explain my results........

An example of sorts as an illustration of explanatory satisfaction: many years ago a student came in with a sand dollar and shot a nice hologram of it, but it had a black spot on it surrounded by rings of an orderly spectrum blue-gtreen-yellow-red, totalling maybe a centimeter in diameter. Since no TEA was involved, I had some moments of what-the -heck?! Then I looked at and touched the specimen and it dawned on me that parts were still damp, and that the part closest to the emulsion was one of those, so the imbibed moisture swelled the emulsion, with the closest part depositing the highest concentration, which then decreased radially. The black area at point of near-contact was over-swollen into the UV. and thus invisible....
jrburns47
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Re: Rejuvenating old Ilford plates

Post by jrburns47 »

I have a lot of old Ilford plates as well. Two summers ago, I exposed a number of them (532nm) as transmission holograms and got very clear & clean but relatively dim images. No presensitizing of any kind. I used the GP-61 developer, non hardening fix, and the GP 431 bleach - all designed originally for Agfa material - and dried using 4 step alcohol drying. I also exposed some old Agfa 8E56HD plates in the same sequence and got significantly better results. I'm getting ready to try the Ilford material again soon. Based on the results of two summers ago, it seems to me worthwhile to try TEA presensitzation, as well as serious testing of other chemistry. In the meantime, Ed Wesly has recommended trying SM6 chemistry and Hans B has sent me some ideas to try. Regardless, it seems clear to me that the GP-61/GP431 chemistry is inappropriate for Ilford. Since I have a lot of the old Ilford, i would love to hear of any current Ilford success stories.
Din
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Re: Rejuvenating old Ilford plates

Post by Din »

walschuler wrote:Why did the water pre-soak work?
Well, when you soak something, especially something gelatinous, in water, it swells. Should there be local inhomogenities (cracks, displacements etc), then the swelling "fills in" the cracks etc. It may also depend on the pH of the water, especially if it's slightly alkaline. You may also have latensified the film.
walschuler wrote:Why should Jeff's suggestions about pre-exposure dilute bleach and devo have worked and why didn't they??
Presumably because if the AgBr had a very small amount of printout, then the bleach would have reversed that. I don't think that's completely true because the re-halogenated crystals are a different size, otherwise you're simply returning the developed Ag+ back into AgBr. So, it may not have worked because there was no printout. Rehalogenating Ag+ may not have worked because there was no Ag+, the smaller crystal size of the now-recovered AgBr would have needed a higher exposure. There is an inverse relationship between crystal size and energy required to expose it.
Martin
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Re: Rejuvenating old Ilford plates

Post by Martin »

As for hypersensitizing photographic AgX emulsions with water, general wisdom taught that a pre-exposure water soak did remove excessive bromide ions.

I guess I just tried about any holographic AgX emulsion in that respect. Some showed a minor speed increase after a water soak. The only material to be unique I found, was Ilford‘s SP-673 (but not Ilford‘s HOTEC films!). As long as the layer was dry, it was practically useless – due to its very low sensitivity. However, when I exposed the still wet emulsion, I noticed some 20x speed increase. The holograms were very bright. In order to remain visible, they had to be wet. That made them highly vulernable to printout.
walschuler
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Re: Rejuvenating old Ilford plates

Post by walschuler »

Martin---
Your description of the exceptional Ilford SP-673 emulsion with the poor sensitivity when dry and extra speed gain when damp seems like a modern version of wet plate collodion emulsions of the 1800s. I had a student who, with a small amount of help from me, became expert in wet plate and it was striking how critical the dampness was to success. The same unanswered question about this arises: what is the explanation?
Din
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Re: Rejuvenating old Ilford plates

Post by Din »

walschuler wrote:The same unanswered question about this arises: what is the explanation?
It isn't unanswered, Bill. I thought I already answered it.
jrburns47
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Re: Rejuvenating old Ilford plates

Post by jrburns47 »

After a lot of back and forth about the total non exposure response I’ve been experiencing with old (30+ years?) Ilford red sensitive SP696T plates, I think I’ve found the problem. It doesn’t appear to be fogging or dark reaction per se but seems to be gross insensitivity. Without presensitizing it requires a massive exposure. As soon as I start testing my few old HRT BB640 4x5s, I’ll try presensitizing the SP696T and see if that helps. See photo with annotation. Interestingly, it doesn’t seem to be an issue with the Ilford green sensitive SP695T plates which expose normally.
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Din
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Re: Rejuvenating old Ilford plates

Post by Din »

Fogging is dark reaction, at least, one aspect of it. These extremely high exposure seem to be the symptom, not the disease. It's necessary to analyse the disease. By the way, these figures in ergs, are they what your meter is reading? If so, these should be power figures, not energy figures.
jrburns47
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Re: Rejuvenating old Ilford plates

Post by jrburns47 »

Meter is reading in mw & uw. I know that as a theorist you don’t like ergs as an expression of power. Regardless, it’s reasonable to say that 10 ergs=1 microwatt (uw). Ergs were a useful thing when 3mw HeNes were teaching lasers.
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