Topic: C-41 kit capacity?

[Nigel]

Hi guys, I hope everyone is keeping safe and well.

I've finally started processing colour at home. I'm using the Tetenal kit and I'm two batches (four 120 films in).

In the instructions, it says, "if the user processes predominantly high-speed films (iso 400 and faster) it is recommended that only three development runs (per litre) be done."

That would get me only six rolls of 120 from a kit. On that basis, it would be cheaper (although not as satisfying) to send them to the lab, what do you do?

[Indofunk]

I use it till it stops working. Depending on ambient temperature and time since it was mixed, I can get from 12-24 rolls from a liter. Pretty sure Miguel has gotten even more than that, but whereas I'll develop a roll or two a week, he'll run through all 24 rolls in a couple of days

ALWAYS. DO. A. LEADER. TEST!!! I can't emphasize that enough. Even if you're doing 2 runs on the same day, do separate leader tests before each. As soon as your leader test fails, toss the chems and mix up another batch.

Store the chems (especially developer) in a cool, dark place (I use an air evac container to get as much evil oxygen out of there as possible, you can also do the marble trick) and it should last for months. Oh! And don't let your blix get within the same area code as your developer! A drop of blix contamination will kill your dev in an instant. I use separate pitchers, funnels, and stirring rods for dev vs blix, and wash my Peterson tank after each run more thoroughly than I wash my hands to prevent COVID!

[Francois]

When they put a kit capacity, it only means that processing more film won't guarantee color accuracy. Since you don't print the color negs in the darkroom you don't have to worry about that quite as much.

I remember Al (ChemicAl) used to get insane life out of a single kit. But like Satish said, do a leader test before each batch.

[Nigel]

Thanks guys.

Satish, can you run me through how you do your leader test? I want to develop my own project work, so I want to be as confident I can that I’m going to get results.

[Indofunk]

Simple. You know the end of that 135 roll that you cut off and toss before loading the film into a spool? Keep that leader. It's been exposed to light for god knows how many hours, so when developed it should be completely black. Heat up your chems and dip that leader in developer for the 3.5min and look at it (I usually rinse it quick, then dip it in blix for a minute to make sure that nothing weird is happening and the blix doesn't clear the developed film, but that's not necessary). If your leader is dark, then full steam ahead! If it isn't (or if the blix clears it) then toss it all and mix up a new batch.

[Francois]

That simple. I always keep the film leaders for testing stuff. I usually cut the end and slice it in half. But I could just use a test roll and clip from that.
Just don't mix the B&W and C41 leaders...

[Nigel]

Thanks again, guys. I appreciate the help.

[Francois]

You're welcome. That's what we're here for.

[Indofunk]

That simple. I always keep the film leaders for testing stuff. I usually cut the end and slice it in half. But I could just use a test roll and clip from that.
Just don't mix the B&W and C41 leaders...

Right now I just have a bunch of random 135 leaders lying around for leader tests. Also, I mostly shoot 135, so basically every time I develop, I have a leader. But your post makes me want to "sacrifice" a roll of 135 to be my designated leader test roll. Just clip off a bit every time I need one. Would save me from having random leaders floating around everywhere

[Francois]

I have an old Easter egg metal box for those (it used to be one of those big cream filled egg types).

[MiguelCampano]

I'm 12 rolls deep in a kit I mixed 4 weeks ago, so should be fine until 20 or so rolls. (one liter from Cinestill).

[Indofunk]

Anecdotally, I just had to dump a batch of C41 chems because it failed the leader test. I mixed it back in February, but only used it 7 times since then 



top: new batch of chems I mixed up (some Ektachrome emulsion)
bottom: old, dead chems (Kodak Gold 200)
L > R: developer + blix; undeveloped + blix; undeveloped/unblixed

[Francois]

Nice indication. And yes, the dev was definitely shot.

[Nigel]

Anecdotally, I just had to dump a batch of C41 chems because it failed the leader test. I mixed it back in February, but only used it 7 times since then 



top: new batch of chems I mixed up (some Ektachrome emulsion)
bottom: old, dead chems (Kodak Gold 200)
L > R: developer + blix; undeveloped + blix; undeveloped/unblixed

That's good to know, thanks. It occurred to me at the weekend whether there's any benefit to keeping chems in the fridge? Mine sit in my workshop which is fine most of the year, but gets very warm during the summer. There's nothing about it on the Tetenal kit instructions.