Using Agfa 304 fixer as C41 stop&preblix bath?

[Rudeofus]

I have developed dozens of rolls of C41 film with Tetenal's 2 bath kits and so far found two issues:

1. When I go directly from CD to BLIX, I sometimes get yellow color streaks in my images.
2. The BLIX exhausts noticeably when the bath is reused a few times, long before Tetenal's stated capacity is reached.

I solved the first issue with a regular stop bath between CD and BLIX, but wondered whether some acidic fixer could solve both issues at once. Since I have access to the raw materials for mixing Agfa 304 (200 g/l Sodium Thiosulfate, 50 g/l Ammonium Chloride, 20 g/l Sodium Metabisulfite, pH ~ 4), I wondered whether I could use this to both stop the color developer, scavenge remaining CD-4 (oxidized or not), and take some load off the following BLIX step by eliminating most of the silver halide left over in the CD step. The ingredients for Agfa 304 are so dirt cheap that processing cost would barely increase (and that's the reason I wouldn't want to use Ammonium Thiosulfate).

Has anyone tried this or something along these lines before? Are there any pitfalls I overlooked? Any suggested improvements ?

 

[nworth]

PE is the resident expert on this area of color processing.

I have found that you absolutely need a stop bath between the developer and blix. I had similar and worse problems without it.

I can't see any reason why a low pH fixer wouldn't work before the blix, but I haven't tried it. The most likely horror scenario would probably be some sort of color shift. The usual order for separate bleach and fix (which does work) is to bleach first, but that is because silver salts are created by bleaching, and they need to be fixed out. You are trying to just ease the fixing burden of the blix by getting rid of the undeveloped silver first so that all the fixer in the blix has to do is remove the bleached silver salts. Sounds reasonable.

As has been noted here before, blix is a terribly unstable mixture. The bleaching agent and fixing agent attack each other, and the combination doesn't last long. It is a situation somewhat like Farmer's reducer. In any case, time as well as capacity is a real issue with blix. Once it is mixed, it goes bad after a day or two.

 

[Bob-D659]

You might find the blix isn't happy with the fixer carry over. I use Kodak C41 chems and use a 30 second stop and water rinse after the developer to keep the bleach happier with no dev or stop carry over. Same with RA4 processing in drums to preserve the blix.

 

[Rudeofus]

You might find the blix isn't happy with the fixer carry over. I use Kodak C41 chems and use a 30 second stop and water rinse after the developer to keep the bleach happier with no dev or stop carry over.

Note that Kodak's C41 bleach uses a more aggressive bleaching compound (Ammonium Ferric PDTA) than most other C41 bleaches and especially BLIXes, therefore you may see these problems only with Kodak's dev kits. I'm not sure about Fuji, but Tetenal definitely uses Ammonium Ferric EDTA.

nworth, I have read many many times that BLIXes are not as good as separate bleach and fix steps, but apart from the issues listed above, Tetenal's C41 kit has worked reasonably well for me so far. Yes, the BLIX has limited working solution life, but so does the CD anyway. Who needs bleach and fix living for 6 months if the CD goes bad after 4 weeks?

 

[nworth]

...nworth, I have read many many times that BLIXes are not as good as separate bleach and fix steps, but apart from the issues listed above, Tetenal's C41 kit has worked reasonably well for me so far. Yes, the BLIX has limited working solution life, but so does the CD anyway. Who needs bleach and fix living for 6 months if the CD goes bad after 4 weeks?

I have read the same thing about blix vs. separate bleach and fix. I have had minor problems with the Tetnal 3 bath E-6 kit (excessive density) which has led me to use only the six bath kit. I suspect the Tetnal bleach is more aggressive than most, but residual silver could still be a problem. The use of a fixer before the blix may actually help. The amount of fixer carried over is fairly small, but I suppose it could accelerate the bleach decomposition. Generally, color developing chemicals are used as one-shots, so that shouldn't be a problem.

 

[Rudeofus]

Quite to the contrary, unless you use the Tetenal kit at 48°C, it is recommended for multiple use even in their booklet, and given its price tag anything but multiple reuse would not be economical. This is especially true for hand inversion tanks where 250ml are required for an 135 roll and even 500ml are needed for an 120 roll. Also note, that even if BLIX gradually attacks its fixer, a trace of extra fixer is certainly not going to hurt, apart from that I wash with water between Agfa 304 stop bath and BLIX.

I have just finished processing two rolls of film with Agfa 304 used as stop bath and just from looking at the negs on the spindles I would say that everything looks normal. Scanning and especially RA4 printing will show whether I got uncorrectable color casts, but to be honest, I doubt it.

There are a few issues with Agfa 304 which may reduce its suitability as C41 stop bath: its relatively low sulfite content and its poor buffering. Note that Sodium Metabisulfite does buffer, but most strongly between pH 6.5 and 7.5, and 20 g/l are not only a weak buffer, but may not even provide enough SO32- for properly scavenging remaining CD-4. I will perform some pH measurements to see whether buffering is at least adequate, i.e. whether pH stays below 5.5 after 5 film rolls in 1/2 liter. In future tests I may end up trying a modification of my recipe: 200 g/l Sodium Thiosulfate, 50 g/l Ammonium Chloride, 50 g/l Sodium Sulfite, Acetic Acid ---> pH 4.5. Or maybe just throw more Sodium Metabisulfite into the mix and be done with it ....