Tetenal C-41 kit timing confusion

FujiLove · Aug 29, 2014

I posted this question on another forum but haven't had much feedback. Hoping some home processing gurus on here can help...

I've attached the instructions for the Tetenal C-41 kit, which is based on a 1 litre solution. As I only mix up 500ml, I've been using the times shown for 1-4 films for my first two, the 5-8 film time for my third and fourth etc. The logic being that the smaller volume of chemical degrades at twice the speed, so after 4 films it's at the same stage a 1 litre solution would be after 8 films. Does that sound reasonable, or is that not the way these chemicals react?

The only response I received on the other forum suggested that I should run the first eight films as per the instructions, then throw it away. I can't get my head around this!

Thanks

markbarendt · Aug 29, 2014

C-41 was designed as a standardized process. Development time is 3:15 at 100 degrees, end of story.

That's not to say it just stops working, it just means that some of the developer gets used up, which slows development, and the film leaves behind some contaminants, which slows development too.

C-41 developers normally start out a little too strong, on commercial lines they add contaminants to slow it down when a fresh batch is made, then it is replenished from there as films go through.

If you stick with 3:15 with your Tetenal kit and run one-roll-at-a-time, the first roll will be over developed (a little pushed), the next may be close to "the C-41 standard", the third may be close or a bit under, the forth is probably bordering on a significant under-development.

The actual rate of degradation is a variable. Believe it or not it depends on the film, Portra is different than Gold for example, and on the scenes being shot, and the size of the batch, on the quality of your water, and smaller batches will get dirty/contaminated faster.

What I'm saying is that the directions provided are simply a starting point to get you close, into a usable range, they are not trying to match the exact "industry standard" for C-41 negs.

Adding extra time allows you to reuse un-replenished developer, bleach, etcetera ... Exactly how much to add, well that will need some playing with to find.

Gimenosaiz · Aug 29, 2014

Hello.
I've got the same kit. I mixed up 1L. I followed the instructions (well no exactly because I didn't spent more than 7-9 with the bleach ... and only in the last four rolls). I've developed 10 120mm rolls and 4 135mm. The results for the last 120mm roll were not so bad but quite different from expected so I decided to mix another kit. Anyway, I will give another try to the "exhausted" one (some 135mm old roll) because I'm not sure about the temperature I had that last time ... neither if the roll itself was damaged.
These are from the last roll, a Konica Minolta 220 (cad. 2007):
https://www.flickr.com/photos/123541493@N02/14469789438/
https://www.flickr.com/photos/123541493@N02/14469960737/
https://www.flickr.com/photos/123541493@N02/14654151054/

This one from the previous one:
(there was a url link here which no longer exists)

Hope this helps.
Regards
Antonio

FujiLove · Aug 29, 2014

markbarendt said:
C-41 was designed as a standardized process. Development time is 3:15 at 100 degrees, end of story.

That's not to say it just stops working, it just means that some of the developer gets used up, which slows development, and the film leaves behind some contaminants, which slows development too.

C-41 developers normally start out a little too strong, on commercial lines they add contaminants to slow it down when a fresh batch is made, then it is replenished from there as films go through.

If you stick with 3:15 with your Tetenal kit and run one-roll-at-a-time, the first roll will be over developed (a little pushed), the next may be close to "the C-41 standard", the third may be close or a bit under, the forth is probably bordering on a significant under-development.

The actual rate of degradation is a variable. Believe it or not it depends on the film, Portra is different than Gold for example, and on the scenes being shot, and the size of the batch, on the quality of your water, and smaller batches will get dirty/contaminated faster.

What I'm saying is that the directions provided are simply a starting point to get you close, into a usable range, they are not trying to match the exact "industry standard" for C-41 negs.

Adding extra time allows you to reuse un-replenished developer, bleach, etcetera ... Exactly how much to add, well that will need some playing with to find.

Thanks for that detailed response. I realise that the chemicals are 'used up' over time and guess I imagined that the Tetenal instructions were there to compensate for that. I'm still wondering whether my approach of using two films per timing set for 500ml is the right one, but I suppose I will only know if I test it? I wanted to be as accurate as possible because the next batch of films will be from my vacation and not 'throw away' images, which is why I'm asking rather than testing!

nbagno · Aug 29, 2014

FujiLove said:
I posted this question on another forum but haven't had much feedback. Hoping some home processing gurus on here can help...

I've attached the instructions for the Tetenal C-41 kit, which is based on a 1 litre solution. As I only mix up 500ml, I've been using the times shown for 1-4 films for my first two, the 5-8 film time for my third and fourth etc. The logic being that the smaller volume of chemical degrades at twice the speed, so after 4 films it's at the same stage a 1 litre solution would be after 8 films. Does that sound reasonable, or is that not the way these chemicals react?

The only response I received on the other forum suggested that I should run the first eight films as per the instructions, then throw it away. I can't get my head around this!

Thanks

I've been developing 120 film with this same kit. First 2 rolls w/500ml in my jobo at 3:15. 3&4@ 3:30, 5&6 @3:45 then discard Works great for me.

adelorenzo · Aug 29, 2014

I haven't been keeping track too closely but I just checked and I am at 19 rolls on my current 1 L kit. I did my first batch with it in December and my last batch two days ago so it's going on 9 months old and still working fine although I'll probably replace it soon.

I mix up the whole 1 L batch but in my tanks I am only using 300-600 ml of solution at one time, so in my mind that probably compensates for some of the use.

FujiLove · Aug 29, 2014

adelorenzo said:
I haven't been keeping track too closely but I just checked and I am at 19 rolls on my current 1 L kit. I did my first batch with it in December and my last batch two days ago so it's going on 9 months old and still working fine although I'll probably replace it soon.

I mix up the whole 1 L batch but in my tanks I am only using 300-600 ml of solution at one time, so in my mind that probably compensates for some of the use.

I think you may have the right idea here, mixing the full 1 litre. In my bottles there would then be less exposure to air and I would be following the Tetenal instructions more closely. Think I'll give that a go with the next kit. In the meantime I'll stick to my original plan of two films at each time.

I've finally got my CPP2 fixed, so it's time to get processing

markbarendt · Aug 29, 2014

FujiLove said:
Thanks for that detailed response. I realise that the chemicals are 'used up' over time and guess I imagined that the Tetenal instructions were there to compensate for that. I'm still wondering whether my approach of using two films per timing set for 500ml is the right one, but I suppose I will only know if I test it? I wanted to be as accurate as possible because the next batch of films will be from my vacation and not 'throw away' images, which is why I'm asking rather than testing!

You are right about Tetenal's intent.

You are right about testing too.

Your vacation photos will probably work just fine.

Tetenal C-41 kit timing confusion

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