Can I mix only part of a bag of D76?

Leigh B · Feb 2, 2012

keithwms said:
I'd love to hear about your scientific method.

My wife is a Ph.D. bio-chemist. At the time, she had a very well-equipped analytical lab.

I mixed up a package of commercial developer, then gave her a sample of it (maybe 10%) and
asked if the important ingredients were in the same proportion as in the original batch.
They were not.

I believe she used gas chromatography for the analysis.
I don't remember the details since this was >40 years ago.

Glad you make a good living. So does she.

- Leigh

brianmquinn · Feb 2, 2012

First off, I agree with Leigh.
Mixing part of a bag will not give you the exact same proportions as mixing the whole bag.
However if the bag, jar, can or whatever it is shaken well (back and forth, upside down etc) each time before taking out the amount you need it will work. YES the proportions will vary slightly but it the final mix will me no more worse then making too much to start and trying to use a half bottle of mixed chemistry a year later.

Also I am a Chemist working in a modern lab with over a million dollars of new top of the line gas chromatography, HPLC, Mass Spec etc equipment at my disposal. There is NO way that I could test a full bag of chemistry and a part mixed bag of chemistry and tell you how they differ. It does not work like CSI. It can be done but it requires detailed and expensive methods. Yes, Kodak has those worked out but just to buy columns for a gas chromatography or HPLC machine will run you from $100s to thousands of dollars BEFORE you even start.

Maybe you were very lucky and she had the perfect setup but I doubt it. I could do a quick and dirty test for you with what I have but I will not be able to assure my results.

tkamiya · Feb 2, 2012

I am wondering about something....

I know Kodak had an issue with XTOL where imperfect sealing caused 1 liter bags to go bad prematurely.

If one is buying a larger bag of developer, say D76, and opening it multiple times to take small portions out, how would one seal the bag sufficiently so that the powder does not go bad??

Perhaps the imperfect balance of constituent chemicals aren't all THAT critical. But I am not sure if I'd take that chance. OP bought a huge bag but 1 gallon bag doesn't cost that much and once mixed, lasts 6 months. It's not enough for me to take that kind of chance with my negatives.

Leigh B · Feb 2, 2012

Quoting from the Acufine instruction sheet:

"Never mix partial container quantities."

Boldface in the original document. No other text in that document is presented in boldface.

So it appears that you're possessed of knowledge superior to that of the manufacturers?
Whence does this knowledge emanate?

The fact that you've "done it for years", and are "satisfied with the results" is meaningless.

On a less sarcastic note...

One solution to the problem is to make up "stock" solutions.
Mix the entire contents of the package very thoroughly with a smaller quantity of water, like one quart.
Divide that quantity into four eight-ounce bottles, each completely filled.
Use collapsible plastic bottles, or add marbles.
For use, add eight ounces of stock solution to 24 ounces of water to make one quart of working developer.

- Leigh

Roger Cole · Feb 2, 2012

Leigh B said:
Quoting from the Acufine instruction sheet:

"Never mix partial container quantities."

Boldface in the original document. No other text in that document is presented in boldface.

So it appears that you're possessed of knowledge superior to that of the manufacturers? Whence does this knowledge emanate?

The fact that you've "done it for years", and are "satisfied with the results" is meaningless.

On a less sarcastic note...

One solution to the problem is to make up "stock" solutions.
Mix the entire contents of the package very thoroughly with a smaller quantity of water, like one quart.
Divide that quantity into four eight-ounce bottles, each completely filled. Use collapsible plastic bottles, or add marbles.
For use, add eight ounces of stock solution to 24 ounces of water to make one quart of working developer.

- Leigh

It's far from meaningless that he's been doing it for years and is satisfied - it's the ultimate answer to the question, for him.

Secondly Acufine is not D76. It could be harder to keep uniform.

Thirdly, if I were a manufacturer, I'd try to discourage mixing smaller amounts too. Better for me if you mix the whole thing and throw half away and buy more.

Fourthly, I don't personally do this. But I'm still looking for someone who has tried it and not been happy with the results on film.

keithwms · Feb 2, 2012

Leigh B said:
I believe she used gas chromatography for the analysis.
I don't remember the details since this was >40 years ago.

Ah so what she proved, by using GC (!) is that the proportions aren't exactly the same. So....? And so for 40 years you have assumed that it mattered?

~~~

Anyway.... enough, obviously this becomes an issue of personal belief, no point in taking it further. If anybody wants to spend more money unnecessarily, be my guest! Maybe it's good for Kodak.

Leigh B · Feb 2, 2012

Roger Cole said:
it's the ultimate answer to the question, for him.

Hi Roger,

I agree completely. The end result is the only thing that matters for each of us.

But that's not the right criterion to use when answering a newbie's question.
He won't have the same goals and standards as anyone else.

As anyone who has taught knows...

You start by teaching the basics and the rules.

Then you teach the student to understand the rules so he knows when and how to break them.

- Leigh

keithwms · Feb 2, 2012

Roger Cole said:
Fourthly, I don't personally do this. But I'm still looking for someone who has tried it and not been happy with the results on film.

LOL you'll probably never find any! You're much more likely to find someone who had a batch of D76 "go bad". Plenty of references online to that.... and then the obvious solution is toss it out. So rather than mixing up what you will actually use... ah never mind.

Anyway, like I said, it starts to become an issue of personal beliefs, and some people will simply never set that aside, no sir, no matter what. Call me odd but when somebody tells me I absolutely can't do something, well then that's something I simply have to try and see for myself. I have learned many surprising things along the way.

tkamiya · Feb 2, 2012

How are you sealing the bag so moisture and oxygen doesn't get in?

keithwms · Feb 2, 2012

tkamiya said:
How are you sealing the bag so moisture and oxygen doesn't get in?

You first toss the bag between your hands and mix it well. You can easily do that. Then you divide the bag into halves ... without breaking the seal... and twist it with roughly half the mix in one part of the bag. You can be as exacting with that as you please, but it's pretty easy to get a half-half division. Then you squeeze the bag such that the half you want to store is completely unable to see air; you can twist it and tightly tie it off and it'll be totally fine. Then and only then you cut it and voila. Easy.

tkamiya · Feb 2, 2012

I'm simply amazed that actually works.... how long are you able to keep your divided D76 powder fresh that way?

keithwms · Feb 2, 2012

Ad infinitum. I mean, I dunno, I mixed some the other day that was at least a year old. Look, if you do it right there will be zero air exposure to the sealed part. Can't remember the last time I bought D76 or ID11. Years ago. I have the stuff sitting around. Unlike some developers it is extremely robust in dry form. I have some from 1976 down in the lab that I should try, I bet it's still okay.

tkamiya · Feb 2, 2012

Very interesting - thanks. I guess D76 isn't as sensitive as XTOL then. I was thinking more elaborate methods are required. We all heard of Kodak's woe with XTOL 1 liter bag and sealing issues.

Roger Cole · Feb 2, 2012

Wow, I wouldn't have thought of that, because I'd be SO sloppy with getting it divided evenly. I'm not one to argue that great precision is needed when it clearly is not, but I'd want to either weigh or measure it somehow. That would involve exposing it to air but then if you get the air out before resealing it (excepting that between the bits of powder of course) it wouldn't likely last as long as the unopened pack but would probably last longer than the mixed stock (which I toss after about six months. I'll be throwing out about half a gallon next month. No way I'll have time to use the nearly 3/4 gallon I have left by then.)

keithwms · Feb 3, 2012

Roger, if you do want to be more precise, you can go ahead and take the half you divide out and weigh that to any desired precision, and adjust liquid volumes accordingly.

But... when I considered the changes people report for compensating differences at 1+1 versus 1+2 and 1+3 etc, I concluded that even if I were off by a bit, it very likely wouldn't matter. I mean, nobody talks about 1.1+1 being different from 1+1... so as we like to say in the lab, don't sweat the petty things, and conversely, don't pet the sweaty things.... Seriously, so much of photography is knowing what not to sweat and placing emphasis where it should be, on the art and enjoyment thereof.

In any case, the half you decide to stow away sees no air....

Roger Cole · Feb 3, 2012

You're right of course. Being anywhere in the ballpark should be close enough.

dehk · Feb 3, 2012

Mix them all put them in 2L pop bottles, problem solved.

Steve Smith · Feb 3, 2012

Leigh B said:
The fact that you've "done it for years", and are "satisfied with the results" is meaningless.

In what way is it meaningless?

If I get the results I want by doing something I'm not supposed to do, I'm going to carry on doing it that way.

Steve.

KarnyDoc · Feb 3, 2012

For those wondering how to store D76 so air and moisture don't get to it, the solution would be to vacuum seal it in a container.

Oh, and the equipment could be found in your kitchen, if you have a FoodSaver vacuum sealer with a canning jar accessory. (I once used my mother's to seal coffee in such a jar. The experiment worked.)

Dieter

RalphLambrecht · Feb 3, 2012

keithwms said:
What did you do Leigh, leave one side open for a day? Must have. I'd love to hear about your scientific method. My result is clear that it works well. P.S. don't presume to lecture me on science, it's what I get paid handsomely to do.

ok
you can afford to order the next round then!

markbarendt · Feb 3, 2012

keithwms said:
Seriously, so much of photography is knowing what not to sweat and placing emphasis where it should be, on the art and enjoyment thereof.

Great point Keith.

keithwms · Feb 3, 2012

RalphLambrecht said:
ok
you can afford to order the next round then!

It'd be my great pleasure Ralph, and I hope that you will set aside some days to come down see me next time you're in my neck of the woods- trust me you'll love it. I'm also up in DC 3 days /wk now so I could also meet up there some time. I need to collect your signature on the book

keithwms · Feb 3, 2012

KarnyDoc said:
For those wondering how to store D76 so air and moisture don't get to it, the solution would be to vacuum seal it in a container.

Oh, and the equipment could be found in your kitchen, if you have a FoodSaver vacuum sealer with a canning jar accessory. (I once used my mother's to seal coffee in such a jar. The experiment worked.)

Dieter

The wine bottle thingies work extremely well too.

Generally speaking though, I believe (only believe! no long term data for every photo chem out there) it to be best to store under inert gas rather than under vacuum, if a really long term storage is required (many months or longer). The reason is well known to chemists: when a seal is under vacuum, it eventually tends to leak into the area you want to protect. If the valued contents are at atmospheric pressure or better yet at a positive pressure relative to atmophere, then the seal will typically behave even better, and even if a minor leak does develop it will leak out, and you'll be able to spot the leak pretty quickly. Also if air transport is required, you have to watch out for the pressure difference which can affect a seal. Hence really high-end or air-explosive chems are typically delivered under positive pressure of inert gas.

I guess I shouldn't tell the story about the student who ignored my admonitions to open a container of fine , nonoxidized metal nanoparticles in a glove box. He said, gee, the bag was all puffy and I sliced it with a knife and suddenly it started feeling kinda hot, and then it started, like, melting, I guess there was something wrong with those particles.... I said congratulations, you just survived a potentially very dangerous situation and if you ever care to risk your life again then please do be sure to let me know so I can keep my distance. Then there was the student with the 1 meter long hydrogen flame, but I digress...

tkamiya · Feb 3, 2012

I've tried those kitchen vacuum sealers myself. Unfortunately, 3 different brands of sealers and bags I used leaked most of the time. Say I seal something and pull a vacuum enough so that bags are tight around the object. Few days later, bags are loser around it. So, apparently, they are made good enough for food but not when air tightness is required.

keithwms · Feb 3, 2012

Yeah, it's a good argument for careful sealing at atmopheric pressure rather than having your valuables at neg pressure. Even the really pricey wine seals do fail eventually. And long before you notice they're failing, they are letting air in. Neg pressure is not advisable for anything really air sensitive.

Can I mix only part of a bag of D76?

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