How to Tackle Slavich Plate Problems.

[jeff-blyth]

Thanks very much for this information.

Do you know if dichromate bleaches are inferior to ferric EDTA ones?

I've been using copper sulphate bleaching, and it seems to work OK, but if I can get better results with other processes that would be great. How much of a difference does it make?

I know that dichromates are quite toxic, and I would prefer not to deal with them, but if they get better results, then it's probably worth using them.

Of course, even with the current process I do as much as I can to minimize/reduce exposure to the chemistry.


What diffraction efficiencies did you see with the various bleaches?

--Ted.

You raise a number of issues that need sorting Ted.
Dichromate bleaches are used mainly as reversal bleaches with no soluble bromide or chloride salt around so that all the developed up silver goes into solution and your diffraction comes from virgin AgBr grains that were there at the start. There are various additional aspects that are well
aired in the lit. One point that is not much mentioned though is that if you
use dichromate with potassium bromide to make a rehalogenating bleach with it, it is such a strong oxidant that it displaces elemental bromine although not very rapidly, so you quite soon start to notice choking
chlorine-like smells coming off!

You ask "Do you know if dichromate bleaches are inferior to ferric EDTA ones?"
There is reason to decide that diffraction efficiency of EDTA-ferric rehalogenating bleach should be higher because virtually all the silver has been repositioned in the emulsion as bromide salt and (ideally )none of it has been lost by going into solution unlike the case of dichromate bleach.
However the hardening of the gelatin around the exposed antinodes by chromium ions can compensate to some extent.

I will show later spectra that indicate the superiority of Ferric EDTA
over copper sulfate by a factor of very roughly 30% . I will discuss it later
and put it here somewhere.

Yes dichromate can be nasty in its soluble form but at least it is involatile and you can easily kill it by chucking it into a container with your old developer solutions. That instantly converts it to an insoluble sludge of basic CrIII compounds.
jeff

[Tom B.]

Thanks for the update, Jeff. Kind of surprising that metol was not helpful for plate rejuvenation. I wonder how metol + ascorbic + alkali (essentially just very dilute developer) would work. Digging around in my fridge, in addition to PFG-03M film, I found some old PFG-01 and Red Star film that had almost totally lost sensitivity. Might be worth trying to revive these too.

Re reflection masters with PFG-03M, I've done this and was able to get bright masters with metol/ascorbic (JD-4) developer and ferric bleach. My reasons for doing this were a bit perverse - I was trying to hide the cosmetic surface defects associated with the very soft emulsion by moving them out of the image plane and copying onto Ultimate film. I forget why I didn't just use the Ultimate film for mastering - maybe I had some PFG-03M plates I needed to use up.

One notable aspect which you've likely run into with BB-640 is that the matching of the humidity of the emulsion during recording and playback is important. If the emulsion requires presoaking for sensitization, then it should be dried with non-heated air at the ambient humidity to be used for playback (or dried with warm air and given lots of time to stabilize at ambient humidity). This can also provide some degree of interactive correction of the master playback wavelength for small wavelength shifts - breathe on the master to swell it, dry with short bursts of warmed air to shrink it, optionally covering the emulsion side with glass to keep the moisture level stable during the shoot.

[jeff-blyth]

Thanks for the update, Jeff. Kind of surprising that metol was not helpful for plate rejuvenation. I wonder how metol + ascorbic + alkali (essentially just very dilute developer) would work. Digging around in my fridge, in addition to PFG-03M film, I found some old PFG-01 and Red Star film that had almost totally lost sensitivity. Might be worth trying to revive these too.

Re reflection masters with PFG-03M, I've done this and was able to get bright masters with metol/ascorbic (JD-4) developer and ferric bleach. My reasons for doing this were a bit perverse - I was trying to hide the cosmetic surface defects associated with the very soft emulsion by moving them out of the image plane and copying onto Ultimate film. I forget why I didn't just use the Ultimate film for mastering - maybe I had some PFG-03M plates I needed to use up.

One notable aspect which you've likely run into with BB-640 is that the matching of the humidity of the emulsion during recording and playback is important. If the emulsion requires presoaking for sensitization, then it should be dried with non-heated air at the ambient humidity to be used for playback (or dried with warm air and given lots of time to stabilize at ambient humidity). This can also provide some degree of interactive correction of the master playback wavelength for small wavelength shifts - breathe on the master to swell it, dry with short bursts of warmed air to shrink it, optionally covering the emulsion side with glass to keep the moisture level stable during the shoot.

On your first point Tom , I have tried mixing ascorbate with metol as a sensitizing bath but the bad affect of metol desensitizing Slavich material is still very
evident.
This unexpected reaction of metol suggests to me that it is messing up
the Slavich sensitizing dyes.


Your second point about humidity control is of course dead right and applies to anybody's gelatin plates.
I resorted to puttingthe plates in a glass desiccator with a saturated solution of a certain salt . It was slightly tricky then keeping the humidity
constant during the exposure.
jeff

[Tom B.]

Hi Jeff - Re humidity control for reflection masters, indeed it applies to all emulsions - thanks for clarifying my carelessly phrased statement.

I tried some quick and dirty experiments on raising film from the dead tonight, and had some partial success. After treatment, the test PFG-03M strip had vastly reduced fog compared to the unexposed control which turned pitch black as soon as it smelled the developer. The sensitivity of the test strip was not very good - still in the light-to-mid grey range with 450 uJ exposure. Not expecting much, I was stepping from 0 - 450 uJ in 150 uJ steps.

I'm fairly certain that this was because, having gone to the kitchen cupboard and discovered that the EDTA jar was empty, I resorted to diluting some old ferric EDTA bleach ( 1 part bleach to 2 parts water) and using that. I suspect that the acid incoporated in the standard formulation dissolved or degraded the sensitizing dyes - which of course is why your recipe did not use acid. I do have ferric sulphate and bromide - maybe the EDTA is an optional nicety? It seems to be unneccesary in Brilland bleach which works well for me. Worth a try? Or I could maybe try to neutralize the acid in the current bath? (after dilution equivalent to 10 mg/l sodium bisulphate) Not having a pH meter, how much sodium carbonate should I add? (if this is even a reasonable thing to do)

I also tried the ascorbic acid/ sodium carbonate treatment on some dud PFG-01 and Red Star film. This increased the sensitivity by at least a factor of 2, and perhaps more, without raising the fog level. Whether this means they can now make better holograms remains to be seen.

The PFG-03M film emulsion was even slimier and more horrible than I remembered from plates - which is strange because I remember when experimenting with the film (December 03) that the emulsion seemed reasonably firm, even able to withstand a squeegee pass or two. At the time I thought that Slavich had switched to a new and improved hardener which had the unfortunate side effect of rendering their film completely fogged and useless, but it is strange that the hardening effect seems to have worn off with time. (though the fog and uselessness persist)

[jeff-blyth]

.........this was because, having gone to the kitchen cupboard and discovered that the EDTA jar was empty, I resorted to diluting some old ferric EDTA bleach ( 1 part bleach to 2 parts water) and using that. I suspect that the acid incoporated in the standard formulation dissolved or degraded the sensitizing dyes - which of course is why your recipe did not use acid. I do have ferric sulphate and bromide - maybe the EDTA is an optional nicety? It seems to be unneccesary in Brilland bleach which works well for me. Worth a try? Or I could maybe try to neutralize the acid in the current bath? (after dilution equivalent to 10 mg/l sodium bisulphate) Not having a pH meter, how much sodium carbonate should I add? (if this is even a reasonable thing to do)

I also tried the ascorbic acid/ sodium carbonate treatment on some dud PFG-01 and Red Star film. This increased the sensitivity by at least a factor of 2, and perhaps more, without raising the fog level. Whether this means they can now make better holograms remains to be seen.

The PFG-03M film emulsion was even slimier and more horrible than I remembered from plates - which is strange because I remember when experimenting with the film (December 03) that the emulsion seemed reasonably firm, even able to withstand a squeegee pass or two. At the time I thought that Slavich had switched to a new and improved hardener which had the unfortunate side effect of rendering their film completely fogged and useless, but it is strange that the hardening effect seems to have worn off with time. (though the fog and uselessness persist)

Yes too much acidity is likely to damage those dyes.
The EDTA is certainly not an "an optional nicety" I'm afraid. It is the sodium salt part of it which stops the pH dropping through the floor.
The trouble with the raw iron salts is that they are only stable at low pH
unless they are supported by complexation to suitable ligands, EDTA
being supremely good at it. Sodium ferric citrate might also work
but I'm afraid if you put any plain sodium carbonate into plain ferric sulfate solution you will immediately form a sad sludge of ferric carbonate/hydroxide. The other point is that thos Slavich dyes are quite likely to form a complex with ferric salt whereas in the EDTA case the ferric ions are firmly complexed up and not free to cause mischief.
Sorry you will just have to replenish your ferric EDTA jar.

....OK Here's a thought, if you really want to try something today make up a 3% citric acid solution then drop in small quantities of sodium carbonate and stir it round gently until it stops fizzing off CO2 gas , then add say Ferric sulfate enough to make it say 1% and see if it works.
Jeff

[jeff-blyth]

.................................
I'm fairly certain that this was because, having gone to the kitchen cupboard and discovered that the EDTA jar was empty, I resorted to diluting some old ferric EDTA bleach ( 1 part bleach to 2 parts water) and using that. I suspect that the acid incoporated in the standard formulation dissolved or degraded the sensitizing dyes - which of course is why your recipe did not use acid. I do have ferric sulphate and bromide - maybe the EDTA is an optional nicety? It seems to be unneccesary in Brilland bleach which works well for me. Worth a try? Or I could maybe try to neutralize the acid in the current bath? (after dilution equivalent to 10 mg/l sodium bisulphate) Not having a pH meter, how much sodium carbonate should I add? (if this is even a reasonable thing to do)

I also tried the ascorbic acid/ sodium carbonate treatment on some dud PFG-01 and Red Star film. This increased the sensitivity by at least a factor of 2, and perhaps more, without raising the fog level. Whether this means they can now make better holograms remains to be seen.

The PFG-03M film emulsion was even slimier and more horrible than I remembered from plates - which is strange because I remember when experimenting with the film (December 03) that the emulsion seemed reasonably firm, even able to withstand a squeegee pass or two. At the time I thought that Slavich had switched to a new and improved hardener which had the unfortunate side effect of rendering their film completely fogged and useless, but it is strange that the hardening effect seems to have worn off with time. (though the fog and uselessness persist)

On third thoughts Tom I think you should get the ready made
iron salt from say Aldrich or Acros to fill up your "EDTA" jar and not make up your own .
This is because the pH is important and the ready made salt leaves the
Slavich plate still incredibly photosensitive. I am amazed how well it works after just rinsing it out and carefully gently drying.

The salt is listed as:-

ethylenediaminetetraaceticacid, iron (III) sodium salt hydrate.

With regard to the "slimey" emulsion problem.
That dev formulation at the start of this thread should help on the basis that it should be so fast (provided your exposure level is reasonable)
that the plate will be in and out of it in not more than 10 seconds and then into an acid stop bath or into that acetic acid-rich bleach formulation at the start of this thread.
jeff

[Tom B.]

On third thoughts Tom I think you should get the ready made iron salt from say Aldrich or Acros to fill up your "EDTA" jar and not make up your own .
<snipped>
With regard to the "slimey" emulsion problem. That dev formulation at the start of this thread should help on the basis that it should be so fast (provided your exposure level is reasonable) that the plate will be in and out of it in not more than 10 seconds and then into an acid stop bath or into that acetic acid-rich bleach formulation at the start of this thread.
jeff

Yes, this sounds reasonable. The citric + carbonate + ferric concoction showed no sign of bleach activity for test chips from developed film or on the fogged film - I probably was off on the pH. My enthusiasm for reviving dead PFG-03M film has dropped, though, with the reminder of its yucky emulsion properties, especially if wet treatment is needed before exposure and development. But the prefab ferric EDTA might be interesting to compare with my usual bleach brew - I'll put it on the shopping list.
Photographer's Formulary http://www.photoformulary.com
has "Ferric Sodium EDTA" at $7.25/10g, $44.25/100g.