There is no doubt that Jeff Blyth’s recommendation of a distilled water rinse before the Pyrochrome or reversal or dichromate bleach eliminates the dreaded precipitate that is almost impossible to eliminate from the emulsion. But is there a chemical additive (and cheap besides) that could be added to a pre-bath to the bleach?
The reason why I am asking is that I have been processing some 70 mm 10E75 film on a hundred foot spiral reel. The tanks need 12 liters, or about 3 gallons American to be filled. I don’t want to use this much distilled H20 and toss it every time, or is it even worth saving after it’s used once?
Would a water-softening agent, like something in the States called Calgon added to the tap water before the bleach do the precipitate preventing job? Or a sequestering agent like EDTA, although that might be pricey, but in small amounts do-able? Or adding something to the bleach itself might prevent this mess? Or a sulfite bath like Kodak used after the similar type of bleach in the old B&W reversal film processing kit?
Any help would be appreciated.
Clearing bath before Pyrochrome reversal bleach
Clearing bath before Pyrochrome reversal bleach
"We're the flowers in the dustbin" Sex Pistols
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Jeffrey Weil
Clearing bath before Pyrochrome reversal bleach
Hello Ed,
I might be totally off base here but I'll give the answer a try.
If the precipitate your talking about is elemental silver the problem is the chlorine in the regular water. Take a bit of silver nitrate, either powder or solution, and put a drop in regular water, you'll see the silver go white, the same dropped into di water and there's no problem.
So, you might try aging regular water to let the chlorine out gas. A single 5 gal bucket from Home Depot would do the trick. If you have some silver salts you could even test it to see how long it would have to sit to remove the chlorine.
The sulfite bath you mentioned might do the trick too, that's a silver solvent. If you've reversed the elemental silver back to halide in the emulsion but have elemental silver on the surface, the sulfite might dissolve the precipitate while leaving the hailed alone......Ok, I just realized you probably knew that already. I'm going to leave it in though to help others, or for them to laugh at me if its totally wrong
I hope this helps.
Jeff Weil
I might be totally off base here but I'll give the answer a try.
If the precipitate your talking about is elemental silver the problem is the chlorine in the regular water. Take a bit of silver nitrate, either powder or solution, and put a drop in regular water, you'll see the silver go white, the same dropped into di water and there's no problem.
So, you might try aging regular water to let the chlorine out gas. A single 5 gal bucket from Home Depot would do the trick. If you have some silver salts you could even test it to see how long it would have to sit to remove the chlorine.
The sulfite bath you mentioned might do the trick too, that's a silver solvent. If you've reversed the elemental silver back to halide in the emulsion but have elemental silver on the surface, the sulfite might dissolve the precipitate while leaving the hailed alone......Ok, I just realized you probably knew that already. I'm going to leave it in though to help others, or for them to laugh at me if its totally wrong
I hope this helps.
Jeff Weil
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Dinesh
Clearing bath before Pyrochrome reversal bleach
10E75 with the pyrochrome process! Oh my lord, that takes me back a few moons!Ed Wesly wrote:I have been processing some 70 mm 10E75 film
Once Upon a Time there was this Agfa
Where we used to shoot a plate or two
Remember how we worked all night till dawn
And dreamed of all the great H2's we'd do
Those were the days my friend
We thought they'd never end
We'd dev and bleach forever and a day
With just the chem we choose
Fringes we'd never lose
For we were young and sure to have our way.
Those were the days, oh yes those were the days
Clearing bath before Pyrochrome reversal bleach
ther is a way of ionizing the water so the Limescale and mineral buildup in the hard water is changed so it will not cling which i thing is very inportant by changing the partical charge. its worth checking intoEd Wesly wrote:There is no doubt that Jeff Blyth’s recommendation of a distilled water rinse before the Pyrochrome or reversal or dichromate bleach eliminates the dreaded precipitate that is almost impossible to eliminate from the emulsion. But is there a chemical additive (and cheap besides) that could be added to a pre-bath to the bleach?
The reason why I am asking is that I have been processing some 70 mm 10E75 film on a hundred foot spiral reel. The tanks need 12 liters, or about 3 gallons American to be filled. I don’t want to use this much distilled H20 and toss it every time, or is it even worth saving after it’s used once?
Would a water-softening agent, like something in the States called Calgon added to the tap water before the bleach do the precipitate preventing job? Or a sequestering agent like EDTA, although that might be pricey, but in small amounts do-able? Or adding something to the bleach itself might prevent this mess? Or a sulfite bath like Kodak used after the similar type of bleach in the old B&W reversal film processing kit?
Any help would be appreciated.
http://www.easywater.com/howitworks.aspx
http://wavehomesolutions.com/content/wa ... nology.cfm
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jeffblyth
Clearing bath before Pyrochrome reversal bleach
Hello Ed.
There is a bit of a problem on your question here.
I know you have for years had to teach youngsters the principle of the “double decomposition” reaction of salts in water. But just to remind others here of the principle. If one mixes different salt solutions together then if there is any combination of the negative and positive ions that can come together to form a precipitate they will automatically do so and it is always the least soluble combination that will form precipitate first.
Very roughly speaking, Ag Iodide is 10 times less soluble than AgBr and AgBr is 10 times less soluble than AgCl.
So the problem of the scatter in reversal bleached holograms where you have not given a good rinse in deionised water after the development step before going into the acid dichromate bath, is not primarily caused by using tap water with its chloride ions. The real problem is caused by the iodide and bromide ions left in the wet emulsion after it has been through the developer.
Even if you don’t add a little potassium bromide to your developer as all traditional photographic devs do (KBr is called a “restrainer”) , soluble iodide and bromide ions are inevitably produced by the development reaction itself. I don’t know the percentage of AgI that Agfa used to mix in with their AgBr in 10E75 emulsion, but my guess is that it was quite high. So once the exposed AgBr is turned into black Ag metal then those accompanying iodide and bromide ions have to be got rid of somehow in the wash water. Or else if they are carried over to the dichromate bath, then as the Ag metal is oxidised by the dichromate, instead of going into solution and being washed out of the hologram to leave you with Agfa’s original AgBr/AgI in the dark unexposed fringes only, you get scattery precipitation of AgBr/I in the light fringes which at this stage are supposed to consist of gelatin only .
Now were you to try using a silver halide solvent to get rid of the scatter then of course you would also start getting rid of your vital AgBr/I in the dark fringes.
However there maybe a bit of leeway here with the help of sulfite solution as you mentioned.
This is because the weak solvent effect of sulfite allows it to be much more effective at removing AgCl than AgBr . However just plain old very hot tap water may manage to do the job alone.
So you could try this:-
1)After the development step give a thorough rinse in running tap water. –It needs to be thorough because soluble Br and I ions are inclined to stick onto the AgBr in the dark fringes and are only slowly washed away. You will then be just left with Cl ions. and no soluble Br or I ions.
2) Then carry out the dichromate /acid bleaching .
cheapest solution to get rid of scatter from AgCl precipitate:
3) Instead of using sulfite solution , just try using really hot tap water (~80-95C) .
There is bound to be some blue shifting in a dried reflection holo but it may be OK.
However I always found the inherent scatter so awful with 10E75 that it was only just good enough for transmission holos and so perhaps you are not making reflection holos with it so blue shifting does not come into it.
Alternative step (3) using sulfite solution.
Possibly the blue shift of reflection holos from the high temperature bath treatment is caused by some gelatin loss as well AgBr loss. So a sulfite bath will avoid gelatin loss at least.
3) rinse in a weak solution of sulfite made up in tap water. Then there will be enough solvent action to remove the AgCl in the emulsion but leave the vital AgBr/I just about unaffected.
I am sorry I do not know what the right concentration of sodium sulfite should be. You will have to do a trial and error test.
Jeff
Off Topic note.
PS. Thanks for your good wishes. And I am glad to hear TJ is doing OK ..
There is a bit of a problem on your question here.
I know you have for years had to teach youngsters the principle of the “double decomposition” reaction of salts in water. But just to remind others here of the principle. If one mixes different salt solutions together then if there is any combination of the negative and positive ions that can come together to form a precipitate they will automatically do so and it is always the least soluble combination that will form precipitate first.
Very roughly speaking, Ag Iodide is 10 times less soluble than AgBr and AgBr is 10 times less soluble than AgCl.
So the problem of the scatter in reversal bleached holograms where you have not given a good rinse in deionised water after the development step before going into the acid dichromate bath, is not primarily caused by using tap water with its chloride ions. The real problem is caused by the iodide and bromide ions left in the wet emulsion after it has been through the developer.
Even if you don’t add a little potassium bromide to your developer as all traditional photographic devs do (KBr is called a “restrainer”) , soluble iodide and bromide ions are inevitably produced by the development reaction itself. I don’t know the percentage of AgI that Agfa used to mix in with their AgBr in 10E75 emulsion, but my guess is that it was quite high. So once the exposed AgBr is turned into black Ag metal then those accompanying iodide and bromide ions have to be got rid of somehow in the wash water. Or else if they are carried over to the dichromate bath, then as the Ag metal is oxidised by the dichromate, instead of going into solution and being washed out of the hologram to leave you with Agfa’s original AgBr/AgI in the dark unexposed fringes only, you get scattery precipitation of AgBr/I in the light fringes which at this stage are supposed to consist of gelatin only .
Now were you to try using a silver halide solvent to get rid of the scatter then of course you would also start getting rid of your vital AgBr/I in the dark fringes.
However there maybe a bit of leeway here with the help of sulfite solution as you mentioned.
This is because the weak solvent effect of sulfite allows it to be much more effective at removing AgCl than AgBr . However just plain old very hot tap water may manage to do the job alone.
So you could try this:-
1)After the development step give a thorough rinse in running tap water. –It needs to be thorough because soluble Br and I ions are inclined to stick onto the AgBr in the dark fringes and are only slowly washed away. You will then be just left with Cl ions. and no soluble Br or I ions.
2) Then carry out the dichromate /acid bleaching .
cheapest solution to get rid of scatter from AgCl precipitate:
3) Instead of using sulfite solution , just try using really hot tap water (~80-95C) .
There is bound to be some blue shifting in a dried reflection holo but it may be OK.
However I always found the inherent scatter so awful with 10E75 that it was only just good enough for transmission holos and so perhaps you are not making reflection holos with it so blue shifting does not come into it.
Alternative step (3) using sulfite solution.
Possibly the blue shift of reflection holos from the high temperature bath treatment is caused by some gelatin loss as well AgBr loss. So a sulfite bath will avoid gelatin loss at least.
3) rinse in a weak solution of sulfite made up in tap water. Then there will be enough solvent action to remove the AgCl in the emulsion but leave the vital AgBr/I just about unaffected.
I am sorry I do not know what the right concentration of sodium sulfite should be. You will have to do a trial and error test.
Jeff
Off Topic note.
PS. Thanks for your good wishes. And I am glad to hear TJ is doing OK ..
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Dinesh
Clearing bath before Pyrochrome reversal bleach
What about exposing the wet, post-wash emulsion to Ammonium Hydroxide? How's the solubility of Ammonium Chloride/Iodide compare with the solubility of the corresponding silver salts?
But it'll shift the reconstruction angle. You won't be able to simply put the plate back in the holder. If the shift is either severe or non-uniform (some parts of the emulsion shrink more or less than other parts), it'll also cause aberrations.jeffblyth wrote:...so perhaps you are not making reflection holos with it so blue shifting does not come into it.
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jeffblyth
Clearing bath before Pyrochrome reversal bleach
Yes Dinesh , ammonium hydroxide can be a useful substitute for hypo (sodium thiosulfite solution) if you want to avoid using oxidable sulfur compounds . But the really strong solutions of NH3 will certainly start removing AgBr and AgI as well making your dark room smell worse than a nappy washing laundry . There is though plenty of scope for having more tolerable dilute solutions that will only really remove AgCl . and I quite like your idea. So Ed could avoid using any DI water in the process. Incidentally from your posting , NH4 Halide salts are all extremely soluble.
I should have mentioned perhaps earlier that after the dichromate bleach bath you obviously need to then rinse well in tap water to get the dichromate bleach out and if you collect your rinsings into a tank rather than let the harmful dichromate
go straight down the sink (nowadays this is illegal) you can easily just kill its high toxicity with sodium sulfite solution or spent developer .
BTW
If anyone has the time to experiment (and facilities) it would be nice to know what sort of result you could get on the reversal bleach "pyrochrome" system if you substituted the dichromate solution for dilute nitric acid .
Thus cutting out nasty dichromate altogether. Diluted nitric acid is not very nasty (unlike the concentrated stuff) and can be disposed off down the sink with plenty of water . .
Jeff
I should have mentioned perhaps earlier that after the dichromate bleach bath you obviously need to then rinse well in tap water to get the dichromate bleach out and if you collect your rinsings into a tank rather than let the harmful dichromate
go straight down the sink (nowadays this is illegal) you can easily just kill its high toxicity with sodium sulfite solution or spent developer .
BTW
If anyone has the time to experiment (and facilities) it would be nice to know what sort of result you could get on the reversal bleach "pyrochrome" system if you substituted the dichromate solution for dilute nitric acid .
Thus cutting out nasty dichromate altogether. Diluted nitric acid is not very nasty (unlike the concentrated stuff) and can be disposed off down the sink with plenty of water .
.Jeff
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Dinesh
Clearing bath before Pyrochrome reversal bleach
How dilute? 0.5M ? I no longer have any Agfa, but I do have conc nitric and I can try it with Slavich VRP.jeffblyth wrote:dilute nitric acid .
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jeffblyth
Clearing bath before Pyrochrome reversal bleach
It needs to be moderately conc.
Try starting with 1 vol conc nitric to 2 vols water.
Jeff
Try starting with 1 vol conc nitric to 2 vols water.
Jeff
Clearing bath before Pyrochrome reversal bleach
Thanks so much Jeff for the info! You are the go-to man for chemistry!
Of course I am not making reflection holos with 10E, either you’d have to be nuts or extremely talented. Just transmission copies and low frequency gratings. And they aren’t so bad, with the Pyro stain keeping the noise down. Virtual zero-order extinction on some!
Next time I process this material again, I’ll start with the hottest tap water, but I don’t think it’s going to be up where you specified, more like 40 – 50 C. It would be kind of poetic justice if I used the hottest tap water on the 10E and the coldest tap water on PFG-03M or Sphere-S GEO-3!
I think that clearing bath formulae that I have seen are like 1% sulfite, but my library is not at hand at the moment.
The nitric bath idea sounds great, again next time I am processing similarly I will give it a shot.
Of course I am not making reflection holos with 10E, either you’d have to be nuts or extremely talented. Just transmission copies and low frequency gratings. And they aren’t so bad, with the Pyro stain keeping the noise down. Virtual zero-order extinction on some!
Next time I process this material again, I’ll start with the hottest tap water, but I don’t think it’s going to be up where you specified, more like 40 – 50 C. It would be kind of poetic justice if I used the hottest tap water on the 10E and the coldest tap water on PFG-03M or Sphere-S GEO-3!
I think that clearing bath formulae that I have seen are like 1% sulfite, but my library is not at hand at the moment.
The nitric bath idea sounds great, again next time I am processing similarly I will give it a shot.
"We're the flowers in the dustbin" Sex Pistols