Developing difficulties with colour film

I've been developing c41 for a little while now since my lab has shut due to covid. I haven't had too many problems so far, most things turn out just fine. I have a big tub of water at the correct temperature and that's enough to keep me withing half a degree for the length of development.

 

The problem I'm having is some of my images come out with discoloured areas. It isn't every shot, and I'm getting better at editing them out, but it would be nice to not have them in the first place. Originally I thought it might be down to over-agitation but I've switched to two smooth inversions and they still appear. Examples below, I've chosen the most egregious offenders

I think its one of two possibilities - A light leak in the darkroom or substandard bleach/fix. Easy to test the blech/fix.. Place the chemical is a bowl and swish one the effected frames in this solution for about double the normal time. Wash in running water and then re-stabilize. Bet this fixes the problem. The C-41 process is actually a blech solution followed by a fixing. An abbreviated process combines the bleach and fix in a single solution, not as energetic. The bleach is iron EDTA and it needs to be oxidized to work. In machine processing an air-stone, like in a fish aquarium is used to give the fluid the needed air and the solution absorbs oxygen and thus restored. Bet your bleach time needs a boost -- extra time will likely do this trick. OK to put the film through the bleach/fix again.

Insufficient bleach-fix would be my guess too.

 

Easily checked by re-blixing and washing the offending negatives. If the patches improve or go away, then it's poor blixing, and you should get fresh blix or increase the time in the blix.

I've switched to two smooth inversions...

Those wouldn't be those stupid slo-mo figure-of-8 inversions shown in a YouTube video would they?

 

If so, that's entirely wrong! The tank should be smartly inverted, held upside down for a couple of seconds, and then righted again. Do this twice per minute.

 

I have no idea where that crazy slow motion inversion idea came from. Some (ignorant) people just make sh*t up and it becomes an internet meme. For no good reason.

Edited July 10, 2020 by rodeo_joe|1

Thank you both for your responses, I'm glad to hear it's likely something fairly easy to fix! My bleach and fix solutions are the oldest chemicals I'm using right now, and I've got them stored in airtight containers with all the air removed... I figured this would help with shelf life but it seems like it's the exact opposite of what I need to do.

 

Previously I got some darkening around the sproket holes in 35 which can apparently be caused by too much agitation which is why I was so cautious, but I'll definitely start doing some more sensible inversions now

C-41 blix is in a continual process of self-destruction from the moment you mix it. It's a shame that all these easy-to-buy kits have blix.

A word or two about EDTA based bleach:

 

The E-6 and C-41 films have dyes incorporated into the various emulsions -- meaning the dyes are placed in the film during manufacturing. These are organic dyes in a leuco state. Leuco is from the Greek meaning white. A leuco dye is colorless, or nearly so, and blossoms becoming vibrant after modification.

 

When color film is developed, exposed silver salts are reduced to metallic silver by the action of the developer. This freshly deposited silver is now subject to attack by oxygen dissolved in the waters of the developer. This action acts as a catalyst. Adjacent dye globules switch their state and blossom.

 

After developing, areas in the film, not exposed in the camera, contain unreduced silver salts and leuco dye. Areas in exposed areas contain metallic silver and blossomed dye. The image is veiled by metallic silver, which is opaque, and the undeveloped silver salts will eventually self-reduce, so it is necessary to remove both by chemical treatment.

 

The bleach solution is somewhat misnamed; its purpose is to convert metallic silver back to a silver salt. The best chemical for this job was Farmers Reducer, a mixture containing potassium Ferricyanide (used for over 100 years without any incidents). The name gets in the way in modern times, so Kodak removed and substituted iron ethylenediaminetetraacetic acid (EDTA), which is a sequestering agent (metal scavenger). The iron content is oxidized, turning the solution ruby red. Following the bleach step, the film is immersed in a fix bath that dissolves away all but a minuscule amount of silver of any kind. Now the organic dyes that comprise the color film display themselves as being full-bloomed. In an abbreviated process, the bleach and fix are combined.

 

Now the dyes are organic and, as such, if not in the correct environment, they will revert back to a leuco state. This happens if the pH is not correct.

 

Exhausted bleach or fix will likely have reduced chemical activity plus, the pH will be incorrect. In a continuous film machine, the bleach is replenished with fresh solution and air is sparged into the solution via an air pump and air-stone or distributor.

 

The purpose of this is to give some insight into the processing of these films.