Making and Maintaining Bleaches for E-6 Process

[Rudeofus]

I added the ferric chloride before the ammonium bromide, what happened then? The EDTA precipitated, I added ammonia again little by little and the precipitate disappeared. I have a dense red solution. My question is, will it still work or should I start again from scratch?

Can you tell me precisely what kind of "EDTA" this was? Was this a sodium salt of EDTA by any chance?

 

[Josaw98]

Can you tell me precisely what kind of "EDTA" this was? Was this a sodium salt of EDTA by any chance?

I had disodium EDTA stored that I did not use, I obtained free acid EDTA by the method you proposed, once washed and dried this was the EDTA that you used.

To prepare the bleaching solution I added the EDTA, which did not dissolve, and added ammonia little by little until it dissolved, the pH rose to 5.3, after that I added the ferric chloride and the low pH until 1, more or less, then a precipitate was formed again, I added ammonia again until it went up to pH 4 where everything was dissolved.

 

[Rudeofus]

I had disodium EDTA stored that I did not use, I obtained free acid EDTA by the method you proposed, once washed and dried this was the EDTA that you used.

To prepare the bleaching solution I added the EDTA, which did not dissolve, and added ammonia little by little until it dissolved, the pH rose to 5.3, after that I added the ferric chloride and the low pH until 1, more or less, then a precipitate was formed again, I added ammonia again until it went up to pH 4 where everything was dissolved.

Ah, now it makes a lot more sense. Yes, EDTA goes in and out of solution depending on pH. This makes it a lot easier than e.g. Ferric Chloride, which will not dissolve easily once you precipitate Ferric Hydroxide.

You procedure was a bit more involved than the one in my instructions, but it will give you the correct product, and once you have bleach accelerator you will be able to work with it.

 

[Josaw98]

Ah, ahora tiene mucho más sentido. Sí, el EDTA entra y sale de la solución dependiendo del pH. Esto lo hace mucho más fácil que, por ejemplo, el cloruro férrico, que no se disolverá fácilmente una vez que se precipita el hidróxido férrico. Su procedimiento fue un poco más complicado que el de mis instrucciones, pero le dará el producto correcto y una vez que tenga el acelerador de cloro podrá trabajar con él.

Ah, ahora tiene mucho más sentido. Sí, el EDTA entra y sale de la solución dependiendo del pH. Esto lo hace mucho más fácil que, por ejemplo, el cloruro férrico, que no se disolverá fácilmente una vez que se precipita el hidróxido férrico. Su procedimiento fue un poco más complicado que el de mis instrucciones, pero le dará el producto correcto y una vez que tenga el acelerador de cloro podrá trabajar con él.

Yesterday I called a local supplier to see if they had ammonium bromide available, not only did they have it available, they had it at a great price.

I studied a little more about L-Cysteine and compared it to the other bleach accelerators discussed earlier in this thread, place a developing slide film in the first developer and then apply a stop bath so you can cut a small strip and continue with the process. Once the pre-bleach was applied, without washing, I put the film in the bleach and monitored the bleaching process with an open tank. The result? The film was completely bleached within 3-4 minutes. After developing the strip and getting good results, I developed the rest of the film, right now it is drying, I still need to do more tests with different films and make a comparison between L-cysteine and thioglycolic acid but I imagine that if I had not worked the L-cysteine bleaching would not have been carried out and I would end up with a very dense slide, or not? L-cysteine has the advantage, like Mercaptotrizole, of not having an unpleasant odor.

The film I developed was Fujichrome Provia 100F in 120 format, I made a mistake in the exposure in the camera and I shot it at ISO 200, so I applied a +1 push in the developer.

 

[koraks]

Yesterday I called a local supplier to see if they had ammonium bromide available, not only did they have it available, they had it at a great price.

Which reminds me - would you mind having a look at this thread please, and perhaps, if you can, share some advice with your fellow countryman? https://www.photrio.com/forum/threads/darkroom-chemicals-in-mexico.205936

 

[Josaw98]

Which reminds me - would you mind having a look at this thread please, and perhaps, if you can, share some advice with your fellow countryman? https://www.photrio.com/forum/threads/darkroom-chemicals-in-mexico.205936

Thanks, I had not seen this!

 

[Rudeofus]

I studied a little more about L-Cysteine and compared it to the other bleach accelerators discussed earlier in this thread, place a developing slide film in the first developer and then apply a stop bath so you can cut a small strip and continue with the process. Once the pre-bleach was applied, without washing, I put the film in the bleach and monitored the bleaching process with an open tank. The result? The film was completely bleached within 3-4 minutes. After developing the strip and getting good results, I developed the rest of the film, right now it is drying, I still need to do more tests with different films and make a comparison between L-cysteine and thioglycolic acid but I imagine that if I had not worked the L-cysteine bleaching would not have been carried out and I would end up with a very dense slide, or not? L-cysteine has the advantage, like Mercaptotrizole, of not having an unpleasant odor.

It would be great to know, whether L-Cysteine works, since it is much more available than all the alternatives. Regarding "bleached in 3-4 minutes" I would like to remind you of fixing: it's really fixed at twice the time it takes to visually fix the film. The same may apply here: if it takes 3-4 minutes to visually bleach the film under these conditions, then a full bleach may require up to 8 minutes, which is longer than E-6 spec, but still very manageable for us amateurs.

Looking forward to read your results from Thioglycerol vs. Cysteine!

 

[lamerko]

I would be interested too. This Mercaptotrizole chemical is €15 for 5g, but probably one gram will be unusable due to its volatility.

 

[Rudeofus]

I would be interested too. This Mercaptotrizole chemical is €15 for 5g, but probably one gram will be unusable due to its volatility.

Not sure where you got this price quote from, I don't remember paying nearly as much for it. Also, Mercaptotriazole is not volatile IMHO, it's been sitting in its glass for ages ...

 

[lamerko]

Well... this offer was made to me by Suvatlar - he was the only source I found. Maybe it's good to specify that the price is without VAT
Regarding the volatility - I haven't opened the bank, but I can see that the dust is stuck to the glass.
If you know of another source in Europe, I would be grateful if you could share it.

 

[Josaw98]

Looking forward to read your results from Thioglycerol vs. Cysteine!

Well, after some waiting, thioglycolic acid finally arrived on Wednesday. Today I was able to do some tests.

I say it once and for all, at first glance it seems that a Pre-bleach with cysteine works just like a Pre-bleach with thioglycolic acid. Right now I don't have a comparative photograph but I hope to have it soon.

The company that sold me thioglycolic acid states that the concentration can vary between 80 and 90%, I think this will depend on the batch, the label mentions that the bottle I received has a concentration of 88%. For the test, make two Pre-bleach solutions, both 500ml, solution 1 contains 0.23g of L-cysteine, solution 2 contains 0.2ml of thioglycolic acid (88%). The test film was Ektachrome E100 in 35mm format. I developed the film in its entirety until the color developer part, after that I divided the film into 2 parts to be able to apply the different Pre-bleachers, after that I applied the bleach for 6 minutes in both cases and applied fixative at the end pars conclude the process. After seeing the two pieces of film and comparing I can say that it looks completely the same, the same Dmax can be seen with the naked eye. I was monitoring the bleach by eye every two minutes and in both cases it could be seen that it was working at the same speed. In total I spent 12 minutes bleaching the entire film, 6 minutes with sample 1 and another 6 with sample 2, so I can say that L-cysteine works as a bleach accelerator.

However, the sulfur smell is not completely eliminated when using L-cysteine, it is still present although not as much as with thioglycolic acid.

 

[lamerko]

This is a great conclusion. I hope there will be a source somewhere in Europe.

 

[Rudeofus]

@Josaw98 great to hear, that the experiment went well, and it's even greater to hear, that Cysteine does the job well! One potential risk with Cysteine could be longevity of the working solution. I believe I have read somewhere, that Cysteine is a reducer, which may well react with aerial oxygen. But I can imagine many cases, where a Cysteine based prebleach freshly mixed is still a lot less hassle than jumping through the burning hoops to obtain Thioglycerol or Mercaptotriazol.

@lamerko if the smell of prebleach is an issue for you, then try to get Mercaptotriazol from Suvatlar. It's is known to work well and it's completely odorless.

@Josaw98 you can use an ICE capable film scanner to roughly check for retained silver. At least in vuescan I am able to obtain a histogram in the IR channel, and over 90% translucency in the IR channel indicates good desilvering of the film.

 

[Josaw98]

@Josaw98 great to hear, that the experiment went well, and it's even greater to hear, that Cysteine does the job well! One potential risk with Cysteine could be longevity of the working solution. I believe I have read somewhere, that Cysteine is a reducer, which may well react with aerial oxygen. But I can imagine many cases, where a Cysteine based prebleach freshly mixed is still a lot less hassle than jumping through the burning hoops to obtain Thioglycerol or Mercaptotriazol.

@lamerko if the smell of prebleach is an issue for you, then try to get Mercaptotriazol from Suvatlar. It's is known to work well and it's completely odorless.

@Josaw98 you can use an ICE capable film scanner to roughly check for retained silver. At least in vuescan I am able to obtain a histogram in the IR channel, and over 90% translucency in the IR channel indicates good desilvering of the film.

I have access to some scanners, I'll do the test, you'll see!

 

[lamerko]

I found a rather interesting Kodak patent for accelerators - US3893858A. They are specifically mentioned
cystine
cystamine
cysteine
One of the tests mentions that L-(+)-cysteine hydrochloride 6 g was added to the bleach. The rest have a pre-bath, where the pH should be quite low. Maybe I'm wrong, but I guess you need cysteine in both the pre-bath and the bleach?

 

[koraks]

One of the tests mentions that L-(+)-cysteine hydrochloride 6 g was added to the bleach. The rest have a pre-bath, where the pH should be quite low. Maybe I'm wrong, but I guess you need cysteine in both the pre-bath and the bleach?

This earlier thread may be of interest: https://www.photrio.com/forum/threa...bleaches-for-e-6-process.199444/#post-2782730
Your mention of cysteine rang a bell. (I'm aware you were involved in that thread, btw; maybe it had slipped your mind in the meantime though.)

 

[lamerko]

Wow, the last 2-3 posts have really blown my mind.
Anyway - cysteine seems to be readily available and not expensive here. Apparently it's used as some kind of food supplement. I also have some Mercaptotriazol.
If I fully expose a piece of film and process it in a black and white developer, I assume a bleach test would be telling?

 

[Rudeofus]

When I discussed this with Ron (aka PE) back then, he wasn't sure, whether the silver built up with a PQ type developer would be comparable to silver built up with PPD type developer. Taken to the extreme (which most likely won't be the case in real life), one could have a bleach with converts 99% of the silver developed with Dektol, but only 50% of the silver built up with CD-3. Or it could be the other way round, or any other ratio altogether. The only way to show what works is to do an experiment.

Therefore I recommend you do both:

1. one clip exposed to daylight, then fully developed in E-6 FD
2. one clip exposed to daylight, then fully developed in E-6 CD

If both bleached and fixed samples show no retained silver, then you should be good to go. Back then retained silver was measured with X ray devices, to which none of us has access. I have already described some ICE capable scanner based technique, however, this technique has never been verified against an X ray measurement. We're way off the beaten path here, so be careful.