C41 in Communal Darkroom

I run the darkroom at my university and at the moment we only have B&W development on offer. We have some paterson development baths and so I want to start offering C41. We have a difficult situation whereby we don't actually know how many people are going through the darkroom which means that we dump the developer to ensure it runs out before it gets 'used up'.

I asked this question to a few people before and the general consensus was that we should do a single shot development but I started to get confused with single shot and replenishers etc. so I gave up with that line of investigation. Nevertheless, two kits seemed to come up; the Fuji Hunt and the Kodak Flexicolor kits. We have the space to buy big kits so I would be willing to do that, just wondering if we can still do single shot or whatever with those?


I'm obviously also open to other suggestions, don't really mind how complex the process is (e.g. don't worry about separate bleach and fix).

clingfilm said:

but I started to get confused with single shot and replenishers etc. so I gave up with that line of investigation.

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Hi, it can be pretty confusing until you understand the principles, which are not spelled out very well. You need to understand that "developer" and "developer replenisher" are two different things. "Developer," aka "tank solution" to commercial processors, is the one that is actually used to develop film. As film is developed, the "developer" gradually gets "worn out." This is where replenisher comes in. Developer replenisher is like an x-tra-strength developer; if you add a specified amount to the used developer, it restores it chemically to the original "developer" specifications.

A commercial processor using replenishment hardly ever needs the plain "developer," only when they first start up their machine. So the manufacturers only sell "replenisher" in the larger sizes. But to allow these processors to make the initial "developer," they have made a thing called "starter" solution (to "start up" a process. The exact use of "starter" depends on the exact style of replenisher, so you need to select it to be specifically useable for your replenisher. The "starter" bottle should have instructions on it; it will be on the order of - begin with a certain amount of "replenisher," then add so much "starter," and finally add a certain amount of water. Once you do this, you end up with actual developer that can be used directly to develop film.

If you try to develop film in straight "replenisher," the result is excess development. When you use the "starter," you do two things, dilute the "replenisher" to lower the developing agent, etc., to spec, and add "byproducts" (that's what the "starter" chemical mimics) that slow down the development. There is a little more going on, but these are the main principles behind it.

A starter solution is also available for bleach, but I don't know if it's necessary - it's mainly a pH adjuster, and the actual chemical concentration of the bleach is not very critical.

If you want to know much more details about the process, especially use of replenisher, look for Kodak's Z-131 publication, the "operating manual" for the C-41 process (it doesn't seem to be on Kodak's website anymore, so you might have to find it elsewhere). Hope this helps.

clingfilm said:

I run the darkroom at my university and at the moment we only have B&W development on offer. We have some paterson development baths and so I want to start offering C41.

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Unless you wlil have LOTS of students processing C-41 film, all the time, you may find it best to dedicate something like 1 week every month when C-41 processing will be available.

The 5L Fuji X-press kit used single shot is a good place to start, it's the full 3 bath dev/bleach/fix setup - avoid the Blix kits if you can. It's easy enough to calculate smaller mixing quantities from the instructions & use it single shot - though a Jobo does make life more efficient in terms of usage of chemistry etc - I calculate approx. 17 rolls of 35mm per 5L kit if you use Paterson tanks one shot, whereas you can double that with a Jobo. The X-press kit is also probably a better bet until you get an idea of demand as C-41 does not last well once mixed to working strength.

Lachlan Young said:

The X-press kit is also probably a better bet until you get an idea of demand as C-41 does not last well once mixed to working strength.

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C-41 working solution can have a very long life if stored properly--in high quality plastic or glass containers, filled, and sealed tightly.

RPC said:

C-41 working solution can have a very long life if stored properly--in high quality plastic or glass containers, filled, and sealed tightly.

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How easy and reliable is it to test after storage? If I come in and pull a jug out of a storage locker from last month, what reasonable assurances do I have that my negatives aren't going to be trashed vs mixing fresh one-shot?

What may work very well for a single or limited user group is not always the best choice for a more open community environment. I've not worked with colour chemistry yet, but the reliability factor would be pretty big in my mind when it came to making a decision about chemistry options.

Luckless said:

How easy and reliable is it to test after storage? If I come in and pull a jug out of a storage locker from last month, what reasonable assurances do I have that my negatives aren't going to be trashed vs mixing fresh one-shot?

What may work very well for a single or limited user group is not always the best choice for a more open community environment. I've not worked with colour chemistry yet, but the reliability factor would be pretty big in my mind when it came to making a decision about chemistry options.

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I use only Kodak chemistry, but many on this site have reported very long life using Kodak and other chemistry when stored properly. Most here report many months with no change in quality; I myself have had developer last years while hardly changing solution color. To get the best possible result, I would check the pH before using and make an adjustment if needed.

I would say it would be just fine for use in a community environment, stored properly.

To rephrase my question slightly: After pulling the jug out of the storage area, what can I do to be confident that the person before me did store it properly?

I've found C-41 developer to be very durable. People are running a dozen rolls or more through some of the kit developers (Rollei, Unicolor, etc.); I've seen it look like sludge and still produce usable negatives. That said, in a shared darkroom, I think one shot is the way to go if you want folks to approach it with any sort of confidence. The Kodak Flexicolor developer is cheap and easy to mix and readily available from Unique Photo. All things considered, it's about 50 cents per roll of 35mm, and a dollar per roll of 120. Everything you need is posted here:
(there was a url link here which no longer exists)

Luckless said:

To rephrase my question slightly: After pulling the jug out of the storage area, what can I do to be confident that the person before me did store it properly?

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To answer you question, though, in case you go the shared route... Keep a supply of undeveloped 35mm color negative film leaders around. Drop one in you developer before use. It should turn black (not brown, not beige) after about five minutes. Optionally you can put a piece of clear tape over part of the leader (emulsion side) so you can see the contrast more easily. The area under the tape won't darken, so you're comparing it to the surrounding (hopefully) darkened area.

I have been developing colour for the past 26 years and had periods of progress and periods of going backwards. However as it has been said before C41 is pretty stable stuff and is pretty reliable. I have settled on buying 2.5l kits of Rolliebase C41 and mix the whole lot in one go, but decant it into 4 x 1/2 litre dark brown glass bottles with the last 500cc decant that into 5x 100cc bottles. I have some I made up perhaps 2 months ago and it is still fully usable. Plastic bottles can be used but many are air permeable so the developer will de-compose relativel quickly.

Fuji Hunt, the professional kis or Fuji Xpress is also very good, but there are I think (from memory) about 5 different bottles of different base chemicals to make up the kit former and I didn't find either to last as long as the Rollie chemicals.

You can buy the bottles quite cheaply from King Scientific 01924 412995.

i would one-shot the Dev, Fix, and Final Rinse, and recycle the bleach (regenerate it with bleach regenerator).

BMbikerider said:

Fuji Hunt, the professional kis or Fuji Xpress is also very good, but there are I think (from memory) about 5 different bottles of different base chemicals to make up the kit former and I didn't find either to last as long as the Rollie chemicals.

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And therein lies the problem - the Fuji/ Kodak 3 bath offers better process quality, but the blix kit might offer better shelf life. The Fuji Hunt kits are very easy to mix btw, just follow the instructions - some basic maths might be needed & a measuring syringe, but nothing more sophisticated than that - the Dev uses an ABC mix, but the bleach is 1+1 dilution & the fix is 1+4.

Luckless said:

To rephrase my question slightly: After pulling the jug out of the storage area, what can I do to be confident that the person before me did store it properly?

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In the case of developer, look at the solution color. If it is dark, on the order of tea or coke color, then air got to it and I would not use it. If lighter, I would use it with confidence. The key is to protect it from air (oxygen). That is why the containers should be impermeable to oxygen and thus made of glass or high quality plastic, filled, and sealed tightly. Over time, these factors are very important.

Bleach is not harmed by air and is known to last months without special storage.

If fixer is slightly yellowed or is turning cloudy, it has oxidized and sulfurized and is bad. Store fixer as you would developer.

RPC said:

In the case of developer, look at the solution color. If it is dark, on the order of tea or coke color, then air got to it and I would not use it. If lighter, I would use it with confidence. The key is to protect it from air (oxygen). That is why the containers should be impermeable to oxygen and thus made of glass or high quality plastic, filled, and sealed tightly. Over time, these factors are very important.

Bleach is not harmed by air and is known to last months without special storage.

If fixer is slightly yellowed or is turning cloudy, it has oxidized and sulfurized and is bad. Store fixer as you would developer.

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Are we talking about reuse? Dyes will come off of just about any color film, affecting the developer color primarily. Colored fixer could also be a sign of carryover. Doesn't mean these solutions are bad, just that they've been used.

Bleach is not only not harmed by air but needs to be shaken up occasionally to revive it.

I am talking unused solutions. When the poster said "the person before me" I was thinking the person who mixed it, not used it; I advocate one-shot use.

RPC said:

I am talking unused solutions. When the poster said "the person before me" I was thinking the person who mixed it, not used it; I advocate one-shot use.

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I figured. And so do I. There's some confusion then as to what this "person before" is doing exactly...

In a community situation, I cannot see reusing chemistry someone else has used before, without testing first, especially with C-41. Not only are you risking oxidation, but contamination by the previous user.

Mr Bill said:

Hope this helps.

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Thanks so much for this response - really cleared it up for me : ) I think I'll steer clear of replenisher, etc.

Prof_Pixel said:

Unless you wlil have LOTS of students processing C-41 film, all the time, you may find it best to dedicate something like 1 week every month when C-41 processing will be available.

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I think you're right. I spoke to Ian C a ton about this privately and he's kind of described how this would work for our darkroom and it seems to be the best balance of quality and convenience. Make a post on our Facebook saying to comment when you've got rolls of film to develop and then when we've got whatever the limit of the 1L solution kit is we make the next 3-4 days C41 days!

Lachlan Young said:

The X-press kit is also probably a better bet until you get an idea of demand as C-41 does not last well once mixed to working strength.

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Are you saying that we would get 17 rolls of 35mm per 5L Hunt kit or per litre of 5L Hunt kit?

Does the X-Press kit last longer than the other C41s? They would be sitting either as a concentrate or powder and then I would break off the 1L quantities as we needed them.

RPC said:

C-41 working solution can have a very long life if stored properly--in high quality plastic or glass containers, filled, and sealed tightly.

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What is your opinion of the plastic accordion bottles like this; http://thumbs.ebaystatic.com/images/g/l6oAAMXQrNtRyslQ/s-l225.jpg

I think ours are super old, but if they're good for storing chemistry in I could buy a whole new set. If not, do you have a suggestion for a different kind?

RPC said:

I would check the pH before using and make an adjustment if needed.

I would say it would be just fine for use in a community environment, stored properly.

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Is pH a good way to measure how well the chemistry is doing? That would make it easier if someone could come in, test the pH of their solution and then be sure that it was going to work/or make an adjustment to make it work

bvy said:

I've found C-41 developer to be very durable. People are running a dozen rolls or more through some of the kit developers (Rollei, Unicolor, etc.); I've seen it look like sludge and still produce usable negatives. That said, in a shared darkroom, I think one shot is the way to go if you want folks to approach it with any sort of confidence. The Kodak Flexicolor developer is cheap and easy to mix and readily available from Unique Photo. All things considered, it's about 50 cents per roll of 35mm, and a dollar per roll of 120. Everything you need is posted here:
(there was a url link here which no longer exists)


To answer you question, though, in case you go the shared route... Keep a supply of undeveloped 35mm color negative film leaders around. Drop one in you developer before use. It should turn black (not brown, not beige) after about five minutes. Optionally you can put a piece of clear tape over part of the leader (emulsion side) so you can see the contrast more easily. The area under the tape won't darken, so you're comparing it to the surrounding (hopefully) darkened area.

Click to expand...

This would be a really good test to do. Does it matter which C41 film we use for this and, if it goes completely dense, does that mean that the developer will definitely work?

BMbikerider said:

I have settled on buying 2.5l kits of Rolliebase C41 and mix the whole lot in one go, but decant it into 4 x 1/2 litre dark brown glass bottles with the last 500cc decant that into 5x 100cc bottles.

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Could you explain this again for me please? What do you mean when you say 'last 500cc'?

clingfilm said:

This would be a really good test to do. Does it matter which C41 film we use for this and, if it goes completely dense, does that mean that the developer will definitely work?

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I approach "definitely" with caution. If the clip darkens, it tells you the developer is not dead -- i.e. it should produce something on the film. That doesn't mean it won't produce a thin negative or bad color rendition depending on other things (how it was mixed, stored, its age, previous use, etc.). The clip test is more useful to keep you from dropping film in developer that is completely dead for whatever reason.

Also, it will work with any color film, though I'm in the habit of using a clip from the film I'm about to develop.