Two films in the same soup?

Just a question...

If I have two rolls of film: Legacy 100 (Neopan) and Pan F+.
I want to develop them in the same developer (D-76 @ 1:1)
I want to develop them for the same amount of time. ( Legacy wants 8.4 min. Pan F wants 8.5 minutes. I don't mind rounding the Pan F down by six seconds to 8.4 minutes.)

Is there any reason I could not develop them in the same batch in one tank?

It seems like a waste of time and resources to develop two batches of film that would seem identical but for the name of the film.

I'm just wondering if there would be any reaction byproducts from one film that would interfere with development of the other film or some such thing.


I'm not averse to doing some experiments and seeing what happens but, as with anything, it is the prudent thing to gather information before forging ahead with any experiment. Right?

I do it all the time.

If you have the same type (classical cubical) films who will need the same developing time it's not a problem at all for a simmultanious development. Fix times should be close together. When mixing Tgrain type film with classical cubical films you have to overfix the last one because fixer time will be more for Tgrain type films so I would not recommend this combination.

You only have to take care of the minimum amount of concentrate for each film but this is the same when doing two identical films.

Best regards,

Robert

I have been calculating my fix times for each batch of film.

When the films go into the tank, I save the piece of the tail clipped off from the end of the film before I reel them up. When I measure out my fixer, I dip the corner of the film clip into the fixer for 30 seconds then I dunk the whole thing in. I use my stopwatch to read the time for the film to clear. (When you can't tell which part of the film was dipped first.) I stop the clock at that point and double the time. If it takes longer than 3 or 4 minutes for the film to clear I will use it one last time then I dump the fixer (into an old bottle for storage and later disposal) and mix up a batch of fresh fixer for the next batch of film.

I suppose I could do the clip test twice and make sure that both films will have a similar fixing time. I could average out the fixing time if there is a difference. What do you say the tolerance should be? Plus or minus one minute? (Calculated clearing time X 2.)

Depends on the fixer, but films like new Tri-X and T-max with magenta dyes take about twice as long as films that don't have these dyes.

What do you say the tolerance should be?

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Within a few minutes I would not make any point of it. But to combine with two extreme type films (Tmax, Tri-X (new) ) 6-8 minutes (depending on type fix) I would not do it.

BTW there is a more precise way to check if your fixer is exhausted by 10ml test fix + 3 drops of KI (Potassium Iodide) when it stays clear the limit of 2 grams Ag+ ions in the fix is not reached yet. It's often sold as fixer tester. You can also count the amount of films (for the working film fix) but the fix capacity is also less (approx. 60%) when fixing Tgrain type films.

I do sometimes myself.

Jeff

I find that 5 minutes fixing is sufficient for TMAX films in my workflow. Other films may be ok in 3 minutes, but there is absolutely no problem fixing them for 5 minutes also. Film cannot be (easily) "overfixed".

Just do it. There's absolutely nothing to worry about it the development times are close enough and there is at least the minimum amount of developer concentrate for the number of films in question as instructed by the manufacturer.

I bought a bottle of Edwal HypoCheck. I use it only as presumptive test while making prints. I find it does not work well for film fixer, especially when reused more than a couple of times.

In the darkroom, making prints, I keep a bottle of it handy to check the fixer in the tray every once in a while. That way I don't have to stop what I'm doing to change out the fixer unnecessarily.

But for film fixer, I find HypoCheck to be inaccurate. On some films, like T-Max, it will read a false positive after only a couple-few rolls of film. On other films, it will read false-negative even after the fixer is beginning to get weak.

Right now, I have a 1-1/2 quarts of fixer that has been used to do at least a dozen rolls of film, Tri-X, Legacy and Pan-F. Two drops of HypoCheck does not get white at all. As of last night's developing session, my clip test was 2 min 45 seconds. (I fixed for 5 min 30 sec.) A fresh batch of fixer will clear that film in under 90 seconds. (For a fixing time of 3 minutes.)

I have fixed only 3 or 4 rolls of T-Max in a similar batch of fixer and HypoCheck turned white almost immediately.

In the darkroom, the stuff works well. Just a drop in the corner of the tray. You can see the precipitate easily under safelight. If one drop turns white then clears after a few seconds, it's time to "demote" the fixer. If it does not clear after a few seconds, it is exhausted and ready to be dumped. (Dumped into an old plastic milk jug to be saved for recycling.)

I clip those tails off my film before reeling them up for development, anyway. They always catch on the reel, anyway. I figure they are useful for "guinea pigs" when getting ready to develop film. It helps me set the exact amount of time to fix the film. It doesn't take very much extra time. I can do it while I'm tempering up my chems while getting ready to start.

Besides, this way, I am damn-straight-sure that my film is going to fix the first time, every time because I saw a piece of that very same film work in my batch of fixer with my very own eyes. If my film clip does not fix the way I like, I have the chance to rectify the problem before I start to work instead of having to take remedial measures after I'm all done.

BTW: I was under the impression that fixing for longer than, say, about 10 minutes can lead to your emulsion becoming contaminated which can then lead to staining down the road if you are not scrupulously careful to wash it out.

I don't think there is such a thing as overfixing. I leave Tmax in rapid fixer for thirty minutes or more all the time, while I go do other things. It's the only way I can stand the 5+ minutes it takes to fix it. Long fixing and washing times are the only things I hate about Tmax. I have recently switched to a two-bath fix for my film. I highly recommend it because it's the only good way to simultaneously get absolute maximum mileage out of your fixer and still make sure your film is always fixed completely with fresh fixer.

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Is there any reason I could not develop them in the same batch in one tank?


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No.

BetterSense said:

I don't think there is such a thing as overfixing. I leave Tmax in rapid fixer for thirty minutes or more all the time ...

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I suspect that 30 minutes is long enough to start reducing density. Would love to hear from those who have quantitative knowledge,

I group different films with similar development times all the time. I am loathe to process a batch if I am doing any fewer than four 35mm rolls or two 120/220 rolls, so I am always picking through my piles of exposed film looking at the pluses and minuses, trying to find rolls with similar times that can be souped together. I usually combine them if the difference is one minute or less.

As Robert said above, clearing times are usually longer with t-grained films. When I mix t-grained films with other films, I just put all the films with the shorter times onto a lift rod and put them on top of the t-grained films, take them out when they are done, and leave the t-grained films in the tank till they are done.

I frequently mix Arista II 400 and HP5+ in the same tank. I've never had any trouble.

The only film developer I use now is Prescysol. This is a staining developer which has the same time (10.5 minutes) for any black and white film.

So yes, I have often processed two different films at the same time.

As for fixing, I would have thought that if you fix for the longest time needed for any of the films, the others would be fine.

I don't time my fix, I just look at it and keep it in there until it's cleared (plus a bit longer).


Steve.

I would be really surprised if the fixing time required for T-Max films would constitute enough "over-fixing" to cause damage to a traditional grain film.

I would, however, recommend using Hypo Clearing agent as part of the workflow, to ensure a sufficient wash.

I started using Hypo Clear when I started clip testing my fixer before using it. Have not had a problem with fixer not working correctly or with unexpected problems with film since. My only concern, now, is to get my developing times set to where I want them to be. The rest of my process is as flawless as I can make it given the conditions I work in.
(i.e. - A home darkroom versus a professional film lab.)

I have no problems mixing films and if 1 film needs to be fixed longer than the other - not a problem. I just fix for the shortest film time first and then remove to wash; the second continues to fix until finished.

I admit, I rarely use TMax film (unless they are gifted to me), but never had a problem mixing and fixing.