Cinestill DF96 monobath

Donald Qualls

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George Mann said:
If I buy this stuff in powdered form for use in my day tank (7 fluid ounces), how many one-shot mixtures will it provide?
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It sounds as if you're intending to divide the dry material and mix partial batches. This is very much not advised. In the case of Df96, it comes with developer and fixer chemicals in two bags, but the developer is a mixture itself and may not divide up evenly.

Now, you could mix it all according to directions, but then you'll get four 7 ounce tanks (and a little left over) if you one-shot it. The stuff is intended to be reused up to 16 times, with time added each cycle; use it any other way and you're on your own. If you want to one-shot a monobath, get some HC-110 and a neutral or alkaline rapid fixer and make up TF-1 (which is my own original HC-110 monobath). The ammonia is unnecessary if the fixer isn't acidic. You could easily store the HC-110 concentrate and fixer concentrate in small vials -- one vial of each, top up to 7 ounces, stir and pour -- for portability.
 

drmoss_ca

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I've run out of Ilford Rapid Fixer, and I'm working my way through a stack of packets of Kodak Professional Fixer from the freezer. An indicator strip says pH4, so I guess that won't work. I wouldn't mind playing with it again, but I really didn't care for the ammonia, which was very strong even when I diluted it to the 5% (as determined by specific gravity 0.979 using a hydrometer. I was using these ratios:
6 parts HC-110
20 parts ammonia
4 parts fixer
70 parts water

Can you suggest an alternative alkali? I do have KOH and NaOH for soap making, but these might be overdoing it!
 

Donald Qualls

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The Professional Fixer is a powder in the packets? That's probably acidified with something like citric acid and sodium metabisulfite. You should be able to still use the ammonia, but adjust the water + fixer to give the same volume you'd have had in the formula you posted.

You could probably also use sodium carbonate, but in all honestly I don't know what the ending pH should be. I planned to experiment with that mix until I got it working right, and it worked on the second try (first was pretty close, just minor adjustment). You could probably get there with plain thiosulfate crystals and ammonium chloride (gives most of the speed of rapid fixer, but not the capacity -- but we don't care about capacity in this case), and check the fixer part of the solution to be roughly neutral (with phenolphthalein or litmus), then fold the ammonia volume into that, so you'd have:

6 parts HC-110
94 parts neutral fixer working solution

Given it's alkaline, you'll still smell some ammonia, but you have to have that to give the rapid fixing action and get the 3-4 minute completion time.
 

drmoss_ca

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Would it sound reasonable to mix the fixer as per packet directions and then add sodium carbonate until it's neutral, then do the 6:94 ratio?

On second thoughts, I think that ought to be:
6 parts HC-110
4 parts neutral fixer
70 parts water
 
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Raghu Kuvempunagar

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How do you come up with these proportions? Is there a principle that you use? Let's say dilution A of HC-110 does N (normal contrast) development in two minutes. So you figure out the dilution of fixer that does fixing of N developed film in two minutes?
 

Donald Qualls

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@Raghu Kuvempunagar That's more or less how I came up with the original HC-110 monobath, yes -- but I came at it the other direction. "Rapid fixer takes three minute, what developer can get me normal contrast in that time or a little less?"

@drmoss_ca If you don't keep 94 parts of something added to the HC-110, you'll wind up with a different dilution, hence different developing rate, hence over- or under-development. With 6 parts HC-110 concentrate to 94 parts "other stuff" you get the Dilution A (1+15) that this monobath was originally founded on. But yes, if you have the means to check pH even at very low precision (as with litmus or phenolphthalein) you could do exactly that -- neutralize the fixer (easier after mixing it with some of the water), add the HC-110, and top up to final volume. So, for 250 ml of final developer, you'd want ~15.6 ml of HC-110, and 94.4 ml of mixed/neutralized rapid fixer.

Also worth noting that if the fixer packet recommends longer than 3 minutes, you're back to finding the right HC-110 dilution to give the right development time, because otherwise you'll overdevelop (or you'll have to adjust temperature and agitation to decrease developer activity -- cooler -- or increase fixing rate -- more agitation).
 

Donald Qualls

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That should be close enough. Remember, you probably need appr. 80F/24C as well, though that and agitation are the main things you'd adjust to get to normal contrast. Warmer increases development; more agitation decreases it (by increasing fixing rate).
 
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Huss

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I was about to develop roll #21 with my current bottle of DF96... but the test strip showed it was done.

Please take moment, thank you.
 

Moose22

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Huss said:
To be fair, none of my other bottles lasted this long. No idea why this one did.
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It was a summer miracle!

I was kind of waiting for you to tell us you also bought a 100' reel of film for $30 so you were doing this for $3 a roll.

Still, if you get 15 good rolls it's not uneconomical at all. Your results have been pretty darned good for so simple a process. I'm just now getting set up to develop my own and my lazy ass has been wondering if I should do this before I bother with the x-tol.
 

Donald Qualls

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drmoss_ca said:
Thanks! I'm rather surprised it used to work for me when I was using a Rondinax with continuous rotary agitation, but it did.
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With Df96, continuous agitation just means you need to either warm up the developer by 5F compared to what you'd need with a 30 second cycle, or you'll be at "pull -1" (for most films). Same is likely true of any monobath -- more agitation just means you need warmer solution to compensate.
 
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Huss

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So I had shot this roll in October, but then had to wait until now to develop because of a move.
There is something so nice about film photography when you forget what was on a roll, develop it, and then those memories come flooding back!

Late afternoon end of summer game.. Just before the weather turned. Parents just kicking back, enjoying each others' company while scouting for future hall of famers!

Leica M3 DS, Rollei 40mm 2.8, Arista 100, Cinestill DF96 Monobath.

 
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