mixing kodak c-41 developer questions

[destroya]

im ready to open and make an initial mix of my kodak c-41 developer/replenisher. I also have the starter.
https://www.uniquephoto.com/chemistry/kodak-c-41-entwickler-flxclr-devr-rplr-3667805
https://www.uniquephoto.com/chemistry/kodak-c-41-entwickler-flxclr-devr-rplr-3667805
I plan to do replenishment on the developer and have a question about chemical longevity. I can mix up my working solution, 1.75 liters and 1 liter for replenishment and keep the rest of the developer in its native A,B,C bottles and store them. or I can mix up the full 20 liters of developer and put it in "bag in a box" bags and store them that way, using the taps on the bags to replenish the working solution. This is how i keep my XTOL that i use for replenishment. im on 3 years of the stock solution in the bag and it works as good as just mixed.

so I am wondering which option will give me the longest lifetime for the chems. I'm leaning towards mixing all the developer and putting it in the wine bags as ive had good lick using XTOL that way. but regardless, what can i expect for the 2 choices in terms of life of the chems. Part C tends to go off faster than the others from my past experience, about 1 year or so unopened and less than 6 months once opened. to make it more confusing, i can also if its a better option put the stock ABC in there own bags as well.

thanks

john

 

[RPC]

I don't know about wine bags but I always mix all of the developer, and put it in glass canning jars filled to the top and sealed tightly and my C-41 and RA-4 developers last years. I would never partially mix concentrates. If your bags work well with XTOL there is a good chance they will work for C-41 so I would go that route over partial concentrates.

 

[WilmarcoImaging]

If you are using a modern multilayer liquid storage bag, this is probably the best possible material for chemical storage that is readily available. The reason for this is the multi-layer construction, often containing ethylene vinyl alcohol (EVOH). Long shelf life packaging materials use EVOH for reasons of low oxygen permeability and resulting long shelf life.

The next best thing for chemical storage, again that is readily available, is PET beverage bottles. For example, colorless and flavorless seltzer (carbonated water) found in your favorite grocery or mega mart. The bottle needs to have "PET" molded on it somewhere, normally the bottom. I use PET bottles am happy with the experience.

Have a look at http://polymerdatabase.com/polymer physics/Permeability.html This gives an idea of the relative oxygen permeabilities of various plastics.

Note that polyethylene, the material our beloved brown one gallon chemical storage bottles are made from, is a very poor material as it relates to oxygen permeability. It's time to retire these brown jugs, especially the accordion versions which collect particulate material that finds its way into film emulsions.

Regarding storage of concentrates vs. mixed solutions, my opinion is to store the chemicals as mixed solutions. This is based on personal experience and reading about others' experiences. The concentrates are highly active, and are packaged in high quality containers using industrial processes. I don't know for certain, but believe that an inert atmosphere (example: nitrogen gas) is used in the filling of the concentrates. When a bottle of concentrate is opened, the oxidation starts immediately, and when returned to an unsealed, partially filled container, oxidation continues. Even in its original container - it is not the same anymore, especially if/when an inert atmosphere is used. My practice is to mix concentrates to their full working volume, and store the solutions (full to the brim) in as many PET bottles as needed for the full batch.

 

[destroya]

thanks