A question for Chemists... Not a simple one... Setting a two-shot system for D-76.

[Juan Valdenebro]

Hello.
I want to set a system for stock D-76 "two-shot" use. My idea is very simple:
I use stock, and everytime, the used stock solution goes from the tank to amber glass bottles filled to the brim, adding some fresh D-76 to the empty bottle before pouring in my just used stock D-76...
How much unused stock, in mililitres, would you add per developed roll, to make things stable just for a second use of that stock during the next near weeks?
So, in this system, stock is used only twice, with some fresh developer used as replenisher, but always stored without air: not perfect for a real lasting system as with D-76R, but probably 100% perfect for two shot use...
I have no way to find the answer: I could just test and compare negative frames after use and reuse, but that would require a real lot of time, film and developer... And I like testing!
Kodak people say 250ml are our best bet for every roll...
How much of those 250ml would you place in the empty bottle before pouring the 400 or 600ml of just used stock for a 35mm or a 120 roll?
I have no education for this: not even for an educated guess...
Thank you!

 

[Juan Valdenebro]

I forgot:
My goal is to do it in a way I can use the same development time for the second roll.

 

[Juan Valdenebro]

Today I found I was using my last D-76 gallon bag too fast, so I did an amateur trick...
These last days I did test 4 half 120 rolls, each half requiring 600ml (total 2400 ml), and 2 half 35mm rolls, each half requiring 400ml (total 800ml), so this morning I had 3200 ml Stock D-76 used once and stored in glass bottles without air, and with that amount I developed only 3 complete rolls...
It was great because I set my times for TX, TMY and HP5+ in D-76 stock, at EI640.
So, as yet I had 600ml of unused Stock, I decided to mix those 600ml with my 3200 ml of recently used (once) stock, to add 200ml of unused stock per developed roll, so now I have a gallon again, and I'd say it can work like new for stock use and discard...
Any comment?

 

[Juan Valdenebro]

Kodak's recommendation is to process 15 rolls with a gallon of D-76 for optimal image quality and developer stability. I want to do more or less the same number of rolls per gallon with my two-shot stock method.

 

[Juan Valdenebro]

A question in parallel:
The tank I use for MF requires 600ml for a roll, no matter if 120 or 220...
Obviously a much thinner tank -and reel- could hold a 120 roll, and that type of tank would require an amount of developer that's much closer to 300ml than to 600ml...
Has someone seen or used something like that for 120? That would be great for stock development.

 

[Paul Howell]

Cant say how much new stock must be added, if I were doing it (likely all wrong) I would just 10 to 20 % additional time for the second roll then discard. I assume you are planning on using just enough D76 to cover a roll, maybe add enough new D76 to make up for any loss of chemistry that might cling to the film and reel and sides of tank, adjust time then see what happens.

 

[Juan Valdenebro]

Cant say how much new stock must be added, if I were doing it (likely all wrong) I would just 10 to 20 % additional time for the second roll then discard. I assume you are planning on using just enough D76 to cover a roll, maybe add enough new D76 to make up for any loss of chemistry that might cling to the film and reel and sides of tank, adjust time then see what happens.

Hello, Paul.
No interest in schemes based upon changing development times, thanks.
I prefer spending more developer.

 

[Rudeofus]

You are trying to replenish a film developer with itself, and AFAIK there's only XTol to do this right. Would a switch from D-76 to XTol be an option?

Regarding the tank: I know of no tank system to use 300ml for 120 type film rolls. However, you can put two 120 type film rolls on a regular spindle.

 

[Donald Qualls]

If you have stainless 220 reels, it should be possible to cut down the diameter of the reel to the minimum needed to hold a 120 roll, and make up a tank to fit with some material like black ABS drain pipe (or use ABS to make a filler to go in your stainless tank to reduce the volume required to cover the film). I don't know if you'll get down to 250 ml per roll, but you should be able to reduce your consumption below 500 ml. Another economy option would be to simply reuse your D-76 stock, following Kodak's recommendations to add (IIRC) 10% to your process time for each roll after the first.

As @Rudeofus suggested, Xtol is currently the only commercial developer tested and recommended for self-replenishment. That said, it appears that LegacyPro EcoPro (an Xtol knock-off) can be used the same way, and there's some reason to hope that the new Adox XT-3 (an Xtol upgrade -- less toxic, more eco-friendly, less dusty when mixing) will also support that use (testing is either about to start or has started). That said, it might be possible to self-replenish D-76; it hasn't been tested this way, as far as I know, so you'd have to start with running control strips or densitometer curves to determine the necessary replenishment rate.

 

[Raghu Kuvempunagar]

You are trying to replenish a film developer with itself, and AFAIK there's only XTol to do this right.

There is this formula for D76 replenisher which OP can make use of if he wants to mix himself:
https://www.photrio.com/forum/posts/1136566/

 

[Donald Qualls]

I do not think your idea falls under "replenishment", because you are always using a mix of fresh + one-time used.

But this is replenishment, with a (wastefully?) high replenishment rate. The OP would be ahead to just reuse the once-used solution for a second roll with 10% longer time (and continue to do so adding another 10% per reuse).

Another option is to follow Ilford's method of making ID-11 replenisher (now that they've discontinued the actual stuff): they just mix the ID-11 A packets to double strength with only a single B packet, and use the resulting solution to replenish ID-11 stock solution. If you have access to ID-11, this would save money over either reusing stock or 1+1 (replenisher costs twice as much per liter as developer, but you use less than half as much of it). Like other low-rate replenishment systems, the recommendation is to discard the working solution and start over once you've used a volume of replenisher equal to the original working solution. They don't give an optimal replenishment rate (recommend using "process control" to set the rate), however, and you can't do this with D-76 because it's a single packet.

As I recall, a major issue for the OP is very limited local availability of either photo chemicals or raw chemicals that can be used, complicated by his fixed-speed shooting method.

 

[MattKing]

On the 300 ml per roll 120 question, that would require either a tank with a very large centre core and reel to match (sort of like a donut) or a very skinny tank with a very tightly curled reel.
Each would require custom tanks and reels, and the latter would be difficult to load and might give you curved film. Both options might also create problems with flow and even development. I'm not sure how one would design a light baffle for filling the donut tank.
One solution to the problem would be to measure the development time with fresh developer, and then the development time with developer used once, and just split the difference. Half the rolls would be developed something like 5% longer than your ideal target, and the other half would be developed something like 5% shorter than your ideal target.
Another solution would be to save a certain amount of used developer each time, and then mix it in with fresh developer at the start of each two development step. After that first development, you would then replace some portion of the volume with fresh developer before the second step. The amounts of initial seasoning required and fresh replenishment required would have to be determined by experiment, and those amounts may very well be different - e.g. 20% seasoning, and 12% replenishment. You may have to use the same "split the difference" approach to times as well.

 

[MattKing]

[EDIT] Actually I just realized that for his proposal to work, he has no choice but to mix fresh + used-once developer at 1:1 ratio and use +50% development time. Otherwise he won't have enough once-used developer left for subsequent runs. Also, I am starting to think it's a neat idea, because it offers an interesting combination of economy, quality and predictability.

This is where a "brain hurts" problem may come in - doesn't each iteration change the activity of the previously used developer?

 

[Juan Valdenebro]

You are trying to replenish a film developer with itself, and AFAIK there's only XTol to do this right. Would a switch from D-76 to XTol be an option?

Regarding the tank: I know of no tank system to use 300ml for 120 type film rolls. However, you can put two 120 type film rolls on a regular spindle.

Hi Rudeofus,
It's not exact what you say: I'm not trying to set a stable system for replenishing D-76 with D-76... That's not possible. I'm just setting a system for developing a few rolls with a D-76 gallon bag using stock solution with the same development time for every roll, but with all that gallon of D-76 used in a short time after decanting it to glass bottles. That is possible.

I've used Xtol, and I like D-76 better for soft overcast light, and I prefer grain/image structure with D-76: I like sharp tight grain.

 

[Juan Valdenebro]

But this is replenishment, with a (wastefully?) high replenishment rate. The OP would be ahead to just reuse the once-used solution for a second roll with 10% longer time (and continue to do so adding another 10% per reuse).

Another option is to follow Ilford's method of making ID-11 replenisher (now that they've discontinued the actual stuff): they just mix the ID-11 A packets to double strength with only a single B packet, and use the resulting solution to replenish ID-11 stock solution. If you have access to ID-11, this would save money over either reusing stock or 1+1 (replenisher costs twice as much per liter as developer, but you use less than half as much of it). Like other low-rate replenishment systems, the recommendation is to discard the working solution and start over once you've used a volume of replenisher equal to the original working solution. They don't give an optimal replenishment rate (recommend using "process control" to set the rate), however, and you can't do this with D-76 because it's a single packet.

As I recall, a major issue for the OP is very limited local availability of either photo chemicals or raw chemicals that can be used, complicated by his fixed-speed shooting method.

Hi Donald,
I have access to ID-11 here, but I don't want to replenish, thanks.
No idea about the fixed speed you mention.

 

[Juan Valdenebro]

@MattKing and @Donald Qualls oops, you guys are right. I just realized that it's impossible to have a steady supply of "used-only-once" developer, therefore Juan's approach cannot be implemented, unless he's willing to alternate between 100% stock and stock:used-only-once batches, which he seems unwilling to do because it would mean using different development times.

Yes, what I want to do is to alternate as you say... I think -soon I'll check that- if I add a good amount of unused stock, to the just once used stock, I may be able to use the same development time.
At least for the very slight use of this gallon I think it will work: 3 rolls developed in total with my gallon, and 200ml of unused stock added per developed roll: as Matt said some time ago, D-76 may not change very much when used stock just once... We`ll see: I'm in the middle of a 35mm TMY roll, and I did the same scene and exposure in two rolls, to develop them with unused stock the first one (done), and with the mix of used once stock and unused stock (probably next week).
Glass bottles, no air, little byproducts, and short time between both developments make me imagine it can work... As soon as I see the second roll developed, I'll know if the second identical development time gives weaker results or not.

 

[MattKing]

Yes, what I want to do is to alternate as you say... I think -soon I'll check that- if I add a good amount of unused stock, to the just once used stock, I may be able to use the same development time.

Your problem is that if you use a mixture of used and new, after development you will be left with used developer that is more "used" than the used developer that you added at first.

 

[Juan Valdenebro]

Your problem is that if you use a mixture of used and new, after development you will be left with used developer that is more "used" than the used developer that you added at first.

Hi Matt,
Only two developments: the first one with stock, and the second one with a mix of used once stock + unused stock, then discard.
The amount of unused stock to add to the gallon of once used stock, per developed roll, is what I asked for...
This time I went for 200ml.

 

[MattKing]

But that requires two different development times, which you are trying to avoid.

 

[YoIaMoNwater]

I feel like everyone is over thinking this problem. OP can use his developer, then fill the used developer into his empty bottle. For the next stage he can just decant 50% of the used developer and mix in with 50% of his stock solution. After developing with this, then just discard the whole thing. The cycle then repeats where he can pour in the full stock developer and after developing the film, store it in the bottle, and then decant 50% and add 50% of stock buffer for the next development.

Basically this will save him 1/2 of required volume for each (or every other?) processing but you must keep track of the number of times you are doing this. I don't know, this just sounds like unnecessary stress but if it can save money/resources then OP can test it.

 

[YoIaMoNwater]

But that requires two different development times, which you are trying to avoid.

Ah, nvm. Didn't realize OP want to avoid adjusting develop time. Yea, not sure how that would work then...

 

[MattKing]

I feel like everyone is over thinking this problem. OP can use his developer, then fill the used developer into his empty bottle. For the next stage he can just decant 50% of the used developer and mix in with 50% of his stock solution. After developing with this, then just discard the whole thing. The cycle then repeats where he can pour in the full stock developer and after developing the film, store it in the bottle, and then decant 50% and add 50% of stock buffer for the next development.

And use something like a 9 minute development time for the first roll, and 9.5 minutes for the second.
Or compromise, and use 9.25 minutes for each.

 

[Juan Valdenebro]

But that requires two different development times, which you are trying to avoid.

True if I don't add unused stock...

 

[Juan Valdenebro]

I feel like everyone is over thinking this problem. OP can use his developer, then fill the used developer into his empty bottle. For the next stage he can just decant 50% of the used developer and mix in with 50% of his stock solution. After developing with this, then just discard the whole thing. The cycle then repeats where he can pour in the full stock developer and after developing the film, store it in the bottle, and then decant 50% and add 50% of stock buffer for the next development.

Basically this will save him 1/2 of required volume for each (or every other?) processing but you must keep track of the number of times you are doing this. I don't know, this just sounds like unnecessary stress but if it can save money/resources then OP can test it.

Very easy...
And for money saving, 1+1, as everyone, or Xtol, as everyone...

 

[MattKing]

True if I don't add unused stock...

Even when do.
For this to work with unchanged times, you need a source of consistent used developer.
The used developer you end up with after developing one roll won't be the same as the used developer you end up with after developing two rolls.