Using the same fixer for BW/C41/E6, is it a good idea? Capacity?

[Anon Ymous]

Ok, maybe I'm cheap, but I'm also lazy. I've made some E6 fixer using ammonium thiosulfate. It's a nearly pH neutral fixer that I've also used for C41 films and works very well. I also used it for few bw films I shot lately and everything works fine so far. As far as I can tell, there's nothing wrong with that, but am I missing something?

Now for the second question, about capacity. According to Ilford's instructions for their rapid fixer, a 1l working solution can be used for 24 135-36 films and has about the same amount of ammonium thiosulfate as my homebrew fixer. There is a fine detail in this case though, bw films are not stripped of all silver, as opposed to E6 and C41 films. Does it practically mean that my fixer's capacity is about half that figure when used for colour films? Or that a colour film "counts" roughly as two bw films? Yes, I know that I can check clearing time and discard it when it's doubled, but your experience/knowledge would be appreciated.

 

[darkroommike]

What follows is mostly supposition based on personal experience. The fixation by-products for B&W vs. Color are very different. I would use separate fixes for both. Have you checked the published capacity of C-41 or E-6 fixers? That would be a place to start, I don't think the "load" on the fixer is any higher since the bleach takes care of the processed silver.

 

[Anon Ymous]

Mike, C41 and E6 use rehalogenating bleaches, so the load on fixer can be much higher.

 

[darkroommike]

Mike, C41 and E6 use rehalogenating bleaches, so the load on fixer can be much higher.

Yeah, forgot that. But I would still recommend checking the capacity of ready made color fixers.

 

[pentaxuser]

I thought that somewhere on Photrio in maybe the not so recent past I had read that C41 fixer is OK for traditional B&W so is in effect a universal fixer but the same isn't true in reverse i.e. B&W fixer is not suitable/ideal( not sure which adjective applies here) for C41

It may have been a statement by PE but I am hazy on this. If my recollection isn't faulty then it might help if the reason for this statement was re-iterated by whomsoever made it - again assuming it wasn't a figment of my imagination.

pentaxuser

 

[Anon Ymous]

Oh, yes, C41 fixer is fine for traditional bw film, it's about using the same solution for all kinds of films that I'm not entirely sure.

Now, regarding capacity of C41 fixer, I found something relevant in Kodak's Z131 manual in section 3. There's a table about the capacity of unreplenished solutions and 8 135-36 films per litre is the number given. Looks like my estimate was rather optimistic.

 

[darkroommike]

Oh, yes, C41 fixer is fine for traditional bw film, it's about using the same solution for all kinds of films that I'm not entirely sure.

Now, regarding capacity of C41 fixer, I found something relevant in Kodak's Z131 manual in section 3. There's a table about the capacity of unreplenished solutions and 8 135-36 films per litre is the number given. Looks like my estimate was rather optimistic.

Kodak suggests 20 rolls per liter for black and white and Ilford suggests 24 rolls per liter so I think you were right about the greater "silver load" when processing color films (any type).

 

[Rudeofus]

In C-41 it is not so much the silver load which limits capacity, rather the kind of silver salts which need to be dissolved. The silver salt with PMT is very insoluble and exhausts fixer at a much lower silver load. The PMT comes from DIR couplers. E6 has more silver than C-41, but doesn't use DIR couplers. I would therefore compare fixer capacity for B&W film with E-6 rather than C-41.

 

[Sirius Glass]

I would use hypo for black & white film and paper. For C-41 and E-6 I would use the fixer in the development kits.

 

[Anon Ymous]

...The PMT comes from DIR couplers...

PMT as in mercaptophenyltetrazole?

 

[Rudeofus]

PMT = 1-Phenyl-5-Mercaptotetrazole. This compound is released during development, when certain DIR couplers do their job, and its pKsp with silver is quite high.

 

[Anon Ymous]

PMT = 1-Phenyl-5-Mercaptotetrazole. This compound is released during development, when certain DIR couplers do their job, and its pKsp with silver is quite high.

That's the same compound used for cooltone print developers, who would have thought.

 

[Rudeofus]

Theory has it, that cool tone is created by heavily restraining development, such that those fewer grains which do develop turn out rather large for the same overall density.

 

[pentaxuser]

I think the answer to part of my statement has been answered, namely that C41 fixer is fine for B&W but my recollection that B&W fixer is either unsuitable or not ideal for C41 is yet to be answered.

Can anyone say whether my recollection is correct or is it a fact that both C41 and B&W fixer are completely interchangeable?

Thanks

pentaxuser

 

[markbarendt]

I think the answer to part of my statement has been answered, namely that C41 fixer is fine for B&W but my recollection that B&W fixer is either unsuitable or not ideal for C41 is yet to be answered.

Can anyone say whether my recollection is correct or is it a fact that both C41 and B&W fixer are completely interchangeable?

Thanks

pentaxuser

It is my understanding that fix is essentially universal until it is put into service. Once it has been used for one type it should not be used for another because of the byproducts of development that carry over.

 

[Photo Engineer]

Color fixer is indeed ok for all films and papers. B&W fixers are generally not suitable for color materials. You can mix products in the fixers as long as you test to insure that there is no retained silver or hypo. Figure that color products use the fixer up at more than 3x B&W products. This is due to the 3 color layers, and the need to remove all of the silver in the coating.

PE

 

[Rudeofus]

@markbarendt : There are two requirements for C-41/E-6 fixer:

1. powerful, fast fixing action, which scavenges Ag-PMT salts of C-41 materials and which can cope with the high silver load from E-6 materials.
   
2. pH of 6.5 for correct dye hues

The first requirement can be somewhat relaxed if long fixer times and fewer fixer reuses are acceptable, but the second requirement is sine qua non. There are neutral B&W fixers (TF-5, ...) which would most likely work well for C-41 and E-6.

 

[markbarendt]

Thanks

 

[Photo Engineer]

And watch out. If you have used fix from a color process, carryover of bleach can take place with poor washing. This can hurt B&W films because the fix becomes a very weak blix and can remove some silver.

PE

 

[pentaxuser]

Thanks PE My decision, if I was mainly a C41 user and an occasional B&W film user would be to use C41 fixer all the time but not the same actual liquid for both C41 and B&W as per your post 19.

pentaxuser

 

[Anon Ymous]

And watch out. If you have used fix from a color process, carryover of bleach can take place with poor washing. This can hurt B&W films because the fix becomes a very weak blix and can remove some silver.

PE

Good to know, thanks.