I was trying to get this thread back to photography.
Hypo heavier than water?
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But we know the photographically relevant answer already! 
It Will Take a While
There must be at least tens of thousands of cubic
miles of ice at the South Pole and Greenland has
a vast amount. Add to glacier and other melts.
Are current minute shifts in the earth's center of
gravity contributing to the recent large number
of earth quakes? I wonder. Dan
There must be at least tens of thousands of cubic
miles of ice at the South Pole and Greenland has
a vast amount. Add to glacier and other melts.
Are current minute shifts in the earth's center of
gravity contributing to the recent large number
of earth quakes? I wonder. Dan
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- RalphLambrecht
- Deleted
But we know the photographically relevant answer already!
Dream on! We haven't even scratched the surface yet!
Well, Ralph, lead us on! What more would you like to discuss?
The differences between cascade washing vs running water for example. Who has test results to compare both methods?
That's a good question! I don't know!
I do know that temperature is a main driving force. There was an article in Photo Techniques in the 90s about washing paper and film that tested many of these issues. I think it was called "The Mystery of the Vortex" or something like that.
I do know that temperature is a main driving force. There was an article in Photo Techniques in the 90s about washing paper and film that tested many of these issues. I think it was called "The Mystery of the Vortex" or something like that.
I have those. They were written by Martin Reed, but cascade washing is not discussed there, if I remember correctly.
Cascade washing makes total sense when you live where water is expensive, delivered by tanker, and can be in short suply etc.
I use a bastardised version for washing films, I often have 2 or 3 dev tanks on the go, and stagger start times to give me ample time to get past stop & fix without problems, but then I put the wash water from the first tank into the second, second into third, an extension of the Ilford wash system. It's worked well for over 30 years.
In my youth I used a 3 tray cascade system for paper (no RC back then) and it was the optimum way of working) but then all commercial work went instantly RC around 1974 and that was the end of it. It was best for volume work, we used to sometimes print a few hundred images 3,4,5 hundred in a session taking turns on exposing or processing and no timer (not my darkroom).
Ian
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I find it problematic in these kind of discussions that people are talking about how powerful or efficient a given washing method is. But, there are at least two different goals; washing in least time, or washing with least water. For some people, efficient and powerful system is quick and for others, it uses only little water. Both are not possible at the same time. Sometimes washing result is mixed in as a parameter, but it shouldn't. Different approaches should be compared so that the washing result is same (for example: passes retained hypo test, but no more).
People who have lots of water, may use running water to keep fresh water on the film surface to enable quick diffusion all the time. On the other hand, the same level of total washing can be achieved with much less water if no running water is used, by letting the diffusion reach the equilibrium and then changing the water. But the diffusion gets slower and slower when it gets closer to the equilibrium.
People who have lots of water, may use running water to keep fresh water on the film surface to enable quick diffusion all the time. On the other hand, the same level of total washing can be achieved with much less water if no running water is used, by letting the diffusion reach the equilibrium and then changing the water. But the diffusion gets slower and slower when it gets closer to the equilibrium.
This is where you're wrong and both Ilford, Kodak and Agfa all have (or had) their recommendations. Efficient washing with shorter times can be done without excessive use of water.
Ian
the way I see it - hypo is basically salt. when you mix distilled water with 'hypo' - you get a uniform solution of diluted hypo according to the proportions in which you mix these two. The only sort of separation that can happen at this point is for the salt to precipitate out of solution, depending on conditions. But PLEASE - understand that the solution as a whole has no 'memory' or will to separate back into 'hypo' and then distilled water! (with the hypo going to the bottom) - if that were the case then the ages old quest to derive potable water from the oceans would be a walk in the park and solved a long time ago. Nor does the ocean's salinity increase as one descends to the benthos. So - what I'm trying to say here is - NO - it doesn't happen - unless, as someone pointed out earlier, you've got polar and non-polar liquids mixed up together - in which case separation will occur.
No, I am not wrong, but maybe the difference is much smaller than I think, and efficient washing can be done quite quickly with just a little more water than slower washing. But, what I said about diffusion speed with regards to hypo concentration in wash water is true. Clearer water keeps diffusion faster, so, changing water more often keeps average diffusion faster and leads to shorter total time. This was shown by one APUG member who measured the water conductivity as a function of time in different washing schemes.
Agitation may have more important role, though, and maybe saving half a minute of time or half a liter of water is not significant.
Traditionally, using running water also provided the agitation and thus lead to much better results.
Ralph, when you say "cascading", I assume for film you mean a "dump and fill" system, and not the cascading system that Ian mentioned that is often used with paper washing?
If it is dump and fill, the dumping is good, but I think the problem there is the time that the top of the reel(s) spend in the water is less than the time the bottom is filled. So unless the tank is filled rather quickly and the volume of water is held in contact with the film for an extended time (which most automated dump and fill washers do not do very well), then one may have good washing on the bottom reels and poor washing on the top reels.
I use a Jobo to wash my 4x5 film - I add 1 liter of water and run the Jobo for 5 minutes and then dump the water and repeat it 4 times. That gives a wash time of 25 minutes with only 5 liters and it ensures that each successive fill has clean water in the tank.
If it is dump and fill, the dumping is good, but I think the problem there is the time that the top of the reel(s) spend in the water is less than the time the bottom is filled. So unless the tank is filled rather quickly and the volume of water is held in contact with the film for an extended time (which most automated dump and fill washers do not do very well), then one may have good washing on the bottom reels and poor washing on the top reels.
I use a Jobo to wash my 4x5 film - I add 1 liter of water and run the Jobo for 5 minutes and then dump the water and repeat it 4 times. That gives a wash time of 25 minutes with only 5 liters and it ensures that each successive fill has clean water in the tank.
Is that true? Don't we turn the tank up-side-down to empty it? If so, the bottom of the reel gets the water first during the fill but is also the first to be without water during the dump. The situation is reversed for the top of the reel, and consequently, top on bottom of the reel have the same time in the water.
Have I missed something?
Ralph, what about development, if Kirk's right then the bottom edge of a sheet of film would be denser than top, in practice it's only really an issue in the tallest Paterson tanks. That's with inversion agitation.
Ian
Ian
As I said, the side receiving the chemistry first is also the side 'losing' it first. Most of my processing is rotation these days, but don't think 'fill and dump' is an issue. If it is, one needs two tanks and dunk the film into a full tank instead. Unfortunately, this may require to do it in the dark.
The stainless steel tanks that hold 6 or more 35mm reels would definitely show some differences between the top and bottom reels in development -- the time it takes to fill through the lids is significant -- which is why with those tall tanks I have read that it is suggested to fill the tank up with developer and then drop in the reels.
In fact, without a pre-soak, I'd worry about developer streaks as the developer works its way past the upper reels down to the bottom of the tank. One has to hold the tank at an angle to fill, so film on one side of the reels might get developer for 30 seconds or so before the other side. (Filling the tanks I usually rotate the tank as I pour).
The draining time (pouring out the developer) may not be as significant as the filling time since even with the tank inverted to drain, the film in the bottom reel would still be coated with developer and a little development would occur until the developer was exahausted locally.
The time it takes to pour in the Stop bath might be significant also.
Vaughn
I was talking about the automated dump and fill washers - I've not seen many of them out there, but I assumed you were talking about those.
As long as you maintain water against the film - and you dump it all out between changes, you'll get the most efficent washing. Then you're limited by the time the amount of time needed for the diffusion process to take place.
I've seen them for film, but you are right, that changes things.
In my view, all points in favor of rotation development.
A Salt Yes
A salt; the sodium salt of hypo sulfurous acid. The
acid is a weak acid. Solutions of sodium thiosulfate
run about neutral. Dan
A salt; the sodium salt of hypo sulfurous acid. The
acid is a weak acid. Solutions of sodium thiosulfate
run about neutral. Dan
Well, it's a little more complicated than a simple ionic salt would imply. Thiosulfate forms complexes with silver halides (hey, another simple ionic salt, right?) and the state of the complex controls the solubility and this the rate of washing.
A Least Water Least Time Method
Least water AND least time? That is one's time in attending the
wash. I've read a lot of posts concerning print and film washing
and have been impressed by the number of darkroom workers
who expend enormous amounts of their time and of the
community's water supply washing film and paper.
Some expend time and and water way way
beyond all reason.
The method I've adopted uses the least amount of water and
the least amount of time in attendance. No magic, for FB paper,
long still water soaks using print separators. Little water is used
so it is jugged and at room temperature. The last soak is
over night. Dan
Least water AND least time? That is one's time in attending the
wash. I've read a lot of posts concerning print and film washing
and have been impressed by the number of darkroom workers
who expend enormous amounts of their time and of the
community's water supply washing film and paper.
Some expend time and and water way way
beyond all reason.
The method I've adopted uses the least amount of water and
the least amount of time in attendance. No magic, for FB paper,
long still water soaks using print separators. Little water is used
so it is jugged and at room temperature. The last soak is
over night. Dan
Using this method, are you not washing out the paper brighteners?
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