Superia 200
How long since the chems were mixed?  Keep reading to find out!

  2016 July 18    Film   Developing


In another article we looked at the question of "How many rolls can you develop with a one-liter C-41 kit?"

Now we ask "How long do the chems last after you mix them?" 

That's also a very good question.  Once again, you probably don't want the developer or blix to run out halfway through a roll of film.

We already know that "Blix"-type C-41 kits will self-deplete and become useless.  Basically we're asking, "When does that happen?"

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In This Article

What "Everyone" Says

Careful Mixing

How Long The Chems Actually Lasted


What "Everyone" Says

If you were just starting out with C-41 home developing, "everyone" would tell you not to waste your time with blix-based kits.  They would warn you that the chemicals would auto-deplete in some unspecified short time. 

Black & white film enthusiasts mix up a gallon of fixer, and if the solution lasts a month, they consider they're doing OK.  If it lasts two months, wow!

Knowing this, I figured that a Blix-based C-41 kit could not last more than a month after mixing. 
When I was still getting more-than-satisfactory negatives after a month, I figured "everyone" might be wrong.

There were a few who said the kit lasted them two months, but then suddenly it stopped working.  From what I could find, it seemed that two months was the hard limit.

Two months?  I thought that sounded pretty good.  If the kit would last two full months after mixing, that was longer than my B&W fixer was lasting.   

Even so, there were still people saying "Don't waste your time!  The chems will lose their strength so fast that you'll hardly be able to use them!"

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Careful Mixing

The Blix solution is the tough one, but developer can also go bad. 

I know from experience that film developer can last longer if you mix everything carefully and don't cross-contaminate it. The instructions for the C-41 kit even tell you not to cross-contaminate.  So, I wondered if some people were mixing their chems uncarefully, and that was why they were depleting so fast.  That, and maybe they were getting blix into their developer, which would kill the chems pretty quickly.

Here's what I would recommend. 

Numero uno:  use distilled water.  Make sure you de-gas the water by boiling it on the stove and letting it cool.  (I think it's clear here that I'm telling you to boil water that's already been distilled, but if not, please read the "Mixing the Chems" section of this, and see also this article, too.  Nowhere on this entire site, ever, have I suggested that you can distill water by simply boiling it and letting it cool.)  Keep the lid on the pot while it's cooling.  This simple thing, I reckon, is one of the most important steps you can take if you're going to develop film, especially color film.

Second thing:  don't cross-contaminate.  I know I mentioned that already, but really be sure of it.  That includes washing off the outsides of the bottles.  Label the caps, so you don't accidentally put the Blix cap on the Dev bottle or something like that.  And make sure there are no droplets of detergent, or film chems, on your work surface.

While you're at it, rinse the funnel between uses.  There shouldn't even be one drop of blix getting into your developer.  It doesn't take much.  This, I think, is where a lot of people are having the shelf life greatly reduced.

Third:  REFRIGERATE the chems after you mix them, and whenever you're not actually using them.  Get a mini refrigerator so you can store the chems separate from your food and beverages.  It helps greatly if you use flexible bottles so you can squeeze the air space out of them each time.  The less air that can get to the chems, the longer they will last. Technically, Blix gets re-generated by aerating it, but this is tricky because you have both oxidizers and reducers together in the same solution. It's a delicate balance that is either the greatest feat of chemical engineering I've seen in a long time, or one heck of a fortunate coincidence.

Either way, I've found that the Blix lasts a long time if you refrigerate it and exclude air.

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How Long The Chems Actually Lasted

Starting out, I hoped I'd be able to say "Wow, the chems lasted for two whole months!"

That would have been pretty darned good.

But, see, I got lazy.  After something like "month-and-a-half, two-months maybe", I thought "Yeah, alright, I'm satisfied that it works;  time to go out and shoot more pictures."  So I left the C-41 chems in the fridge for a long time.

This batch of chems had already developed eighteen rolls.  And I mixed the chems way back on March 21, 2016.

On May 8th I developed a roll, and it looked fine.  That was about a month and half.

But then I lost track of the time.  And what do you know... it was mid-June already.  By now, I figured the chems were spent, just taking up space in the fridge.  Clean 'em out?  Ah, some other time.

But still I thought:  could they still be good??  People said you could get pictures at two months, but after that... blank negatives.  May 21st would have been two months.

A couple times I put the chems out on the counter, let them get to room temperature... and then it was "Nah, maybe tomorrow."

Then July rolled around. 

Mid-July, and there was a roll of Superia 200-- a test roll, really-- but I was hesitant to waste it with an iffy batch of chems.

There was only one way to find out.

So I went ahead and developed the roll with that old batch of C-41.  At nearly FOUR MONTHS old, there was no way this was going to work.  Was there?  The Internet experts would be jeering at the very suggestion. 

I'd already worked out an equation, though, to remove one of the failure modes from the system.  That is, extending the dev times to make up for depletion.  Most people don't do that, and their color negatives are blue-shifted.  And maybe, I guessed, they were thinking their chems were depleted, when in fact they weren't developing the negatives long enough.
According to my equation, at the 19th roll the dev time had to be extended from 3.5 minutes to 6.67 minutes.  Six minutes, forty seconds:  almost double the time.  No one told me how to do this;  I had to figure it out on my own with math and science.  (This is the kind of knowledge that companies pay the big bucks for when they need someone to write instruction manuals.... but often they don't, because they're cheapskates, so they fail... that's a whole 'nother article.)

By this time you probably want to know what the pictures looked like.  With a batch of chems that was nearly four months old.  And had already developed eighteen rolls of film.  In a kit that's supposed to max out at maybe ten or twelve rolls.

Happy Autumn In July!

Canon SureShot 35mm camera

Unicolor C-41 Kit

n=19 rolls
t=6 minutes 45 seconds at 102 F
Blix time = 10 minutes at 102 F

This scan required no special adjustment, beyond what I'd do for any ordinary C-41 scan.  There was no color shifting;  the negatives look normal.  They look as good as Roll #1 from a batch that was mixed yesterday.  This was possible because of careful technique based on sound theory... which means I had to ignore Internet experts who said it couldn't be done. 

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Internet wisdom says the C-41 Kit won't last more than a month, maybe two months at best. 

With good technique, I was able to extend that to some four months.  The negatives look so good that I might try more film with this batch.  Twenty rolls no problem maybe... but twenty rolls when the chems were mixed four months ago?  That's really something.

Follow the techniques that I outlined in this article, as well as How To Develop Your Own Color Film, and you might also get results this good.  Get yourself a kit and give it a try.

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