Except for the ease of doing the process the idea that one uses cascading water or that one uses a number of changes and then tests for retained hypo and proper fixing has a lot to offer in the way of being certain that every wash & fixing has been appropriate.
Ease of doing things, is for me, not very important.
process in the usual way, develop-stop-fix, the use of
two fixers is best.
The wash prerequisite for archival results is a fixer
very little loaded with silver. So, a first fixer is used
to an established maximum silver content then a second
'clean' fixer used to bring the paper's silver load down
to a very low level. Best chemical milage is achieved.
The second fix which is very little loaded with silver
may be moved to first fix.
I use a single very dilute fix as a one shot so achieve
'archival' results with one disposable fix. Works well
with single tray processing. Dan
1. Washing removes fixer - we want to remove fixer from the emulsion and if printing paper, from the paper base. Fixer is necessary to make a permanent image, but needs to be removed once it has done it's work.
2. Washing removes fixation by-products. Fix converts undeveloped silver halides in the emulsion into soluble compounds, and makes washing possible. Washing removes silver fixation by-products from film. Fresh full strength fix makes the most soluble set of silver byproducts possible and therefore the most washable..
Washing must also remove any remaining developer and stop bath in the film.
Let me give a bit more history on washing.
Originally, texts suggested washing film in 5 - 6 changes of running water for about 30 mins to 1 hour. Prints on FB paper were about the same. In one case, it was due to the thickness of the emulsion layer, and in the other it was due to the DW FB paper requiring longer wash. I have alluded to this in previous posts.
Later, Kodak and others developed siphon print washers that used running water and a tray or tank siphon to change the total water in the container on a regular cycle of about 5 - 6 times / hour with normally running water. These recommendations are found in many Kodak publications in the 40s, 50s and 60s.
About that time, due to the concern over the environment, it was thought by some that still water with the same number of changes would give adequate washing. I discussed this with Bill Troop and he feels that much of the driving force came from England which had a water shortage in the 70s. Be that as it may, this practice was promulgated and began to be accepted.
With time, this 5 - 6 change of still water was repudiated by many as being unworkable. Well, the data seems all positive for running water, but variable for still water with agitation and changes. The equations by Mason show why. Buildup of waste products described by CBG in post 56 above enter into the picture as does the quality of the water and the operators expertise such as how well they drain prints and what kind of fixer do they use. It also depends on film and paper!
Therefore, the only "foolproof" method involves washing in running water. Any other method must be tested. In fact, I suggest tests be done with your condition no matter what you use. And, there are three ranges of wash, "normal", "archival" and "too much". Ctein has shown in his article on washing that if you overwash, you can cause problems with your prints just as much as underwashing. There must be just a tiny bit of residual materials left in the coating.
So, this matter is not simple and has no one answer. I say use what works for you, but test and don't overdo. Remember, hard water or film fix for prints can change your wash position totally, and FB prints on paper from one source may behave differently than FB prints from another paper source due to weight, baryta content and calendering.
But "full strength" not by a long shot. My fixers are very dilute.
For each film or paper there is a certain maximum amount of
silver that can be Entirely complexed. I allow for that much
plus a little more. So much silver so much fixer.
I achieve good chemical milage that way. Of course it works
well with the single tray processing method. Or single tube
processing for that matter. Silver levels in the spent fix
are VERY low, 'archival' level. Shorter less water
demanding washes. Dan
I say again!
This dilute fixer must maintain the silver complex solubility during the early stages of washing. I have actually seen dilute fixers work, only to fail when washing starts. Silver halide complexes re-precipitate out into the coating as the wash water begins further dilution and the complexes become insoluable again. They end up in the film or paper. Usually, film is most susceptable, but Baryta FB papers have been known to do this in the Fibre Base.
Sorry, but this is a fact. As many as 4 or more complexes form depending on fixer concentration and they all vary in soluability during the wash. One must be very careful.
You are making a broad statement that is not always true!