Divided D-76: But not the way you think

[Rob-F]

I bought a gallon bag of D-76, because it was only about a dollar more than a one-liter size. But I'd really rather not mix the whole gallon at once. I do have a darkroom scale, so I'm thinking of dividing the powder into--I don't know--maybe four one-quart packets and storing the unused portion in ziplock bags.

Does anyone know how well, and for how long, the unused packets will keep?

 

[Freakscene]

You can't guarantee that the components will be equally distributed among your quarts. You're better off mixing it all up and putting the stock D76 into four one quart bottles and filling them right up.

The dry chemicals will last almost as long as Kodak says unopened packets will if you can keep air out of them.

Marty

 

[wintoid]

Once in a while someone asks this question, and they're always advised to mix the whole thing up. I've never heard from someone who has actually tried it.

Just thinking about this logically, my guess is that if you gave the packet a good shake, you'd be fine splitting this up. I think people overestimate the precision which is required for B+W processing, but then I'm a happy, sloppy darkroom worker.

 

[Freakscene]

I've tried it. it works okay, but I did detect differences in activity between batches. Nothing massive, but enough to be noticeable if you're fastidious.

Shaking may help, but it may make things worse, since the particles of different components in the developer have a different average spread of sizes.

Marty

 

[crawdiddy]

I do this all the time, and it works fine. I've never detected differences between batches. I sqeeze out all the air I can, and double bag in zip locks.

I don't have a precision scale, and so I apportion the batches according to dry measure volume (tablespoons, basically).

As Wintoid says, it's easy to everestimate the precision required for B+W processing.

 

[Ronald M]

It will oxidize from air in the opened package. Kodak packages under nitrogen atmosphere to avoid that problem. It is also not necessarily a uniform mix, but that problem is overblown.

 

[Krzys]

Interesting thread...I am pondering this regarding 5ltrs of XTOL.

 

[Tom A]

I have tried it - and it kind of works. D76 and a film like Tri X has a fairly substantial "slop" factor built in. I suspect that the biggest problem will be powder going bad in the opened packages when air reaches it. Mix it up, as stated, in 4 quart bottles, topped up and with good seals on the caps. Should last at least 1-2 month anyway.
D76 is a typical MQ developer. It doesn't 'die" with age - but gets more aggressive and usually grainier with time.
Of course, the practical solution is to shoot more film and justify a gallon jug of it!

 

[ChrisLivsey]

The manufacturers I suspect don't mix before sealing. That is each component will be added to the "bag" in order then sealed, much like the ready meals production lines which put you off buying them 🙂
This is because mixing is a nightmare, I come from a pharmaceutical background where the consequences of incorrect mixing of a tabletting bulk powder can have grave consequences.
Even if they do mix in bulk then pack down re-mixing is not a simple task.

http://www.in-pharmatechnologist.com/Processing-QC/Less-is-more-when-mixing-powders

Bottom line is, more mixing can separate out layers not mix them.
I fall into the make one lot of solution then split down. If it goes off it cost you a dollar more.
The accuracy may not be critical for darkroom work but I introduce enough variability with technique to look for more.

 

[batterytypehah!]

I've split a gallon bag in two, using digital kitchen scales. It worked well enough but my developing is very infrequent, so both the mixed solution and the second half of powder were sitting around for too long in the end. Consequently, I decided powders were just not for me, and I have no clue if both batches had identical properties or not.