I have posted this before, but Mason, one of the early proponents of the sequential dump and fill showed mathematically and in practice that this method was not as effective as a stream of continuously running water for washing film or paper. He therefore repudiated the dump and fill method. I posted the equations in another thread on this same subject which keeps coming up over and over.
The best wash is a stream of constantly flowing water which is kept up until the photomaterial tests free of hypo residue and silver halide using the appropriate tests. The only way to change this is to change dC/dT or the change in concentration in the photoproduct with respect to time and this can only be changed by changing dD/dT or the change in diffusion rate of the unwanted materials with respect to time.
I've been working on this problem for over 3 years.
And Mason's measure of effectiveness? Successive changes
Originally Posted by Photo Engineer
and soaks though DO work to make more efficient use of
the little water used. A method which uses little water
yet is a practical, easy, quick, way to wash.
I don't believe Ilford in recommending their three changes
of water with agitation have thrown us a bum steer. Dan
I am of the fill and dump school, but with plenty of agitation.
For film I do all the washing in the closed developing tank. The procedure is
1) Water: 30 seconds continuous agitation
2) KHCA: 5 minutes, ten seconds agitation on the minute, I use KHCA to get the purple dye out of the film
3) Water: 30 seconds continuous agitation
4) 3x water: 5 minutes, tens seconds agitation on the minute, this part gets done when cleaning up the darkroom etc. so timing is variable
5) PhotoFlow 1:10 w/ alcohol for stock, then 1:20 w/ distilled water: 30 seconds continuous
Tests in residual fixer test show no color. I don't test as a matter of course after confirming
the procedure works.
Six changes of water in total.
Procedure is the same with sheet film in a Jobo drum/motor base but the agitation is continuous.
I use a similar procedure for prints if I am only washing a few: Large trays, shuffle agitation, longer times.
I use warmish water, 75F or so.
For washing a lot of prints I use a tray siphon and a huge deep tray.
I always check each batch of prints with residual hypo test. I keep a test print or two and run them through the wash with the others just for destructive testing.
Mason worked for Ilford Dan and repudiated this method in his book because it built up a constant amount of hypo and silver salts in each wash, whereas the running water method had effectively zero hypo and silver at the surface of the film as long as the wash continued. He then went on to show it with the math which, as I say, I posted before along with his thoughts.
The rinse and dump method was to be used only in cases where water was limited, and actually Ilford had him design it during a drought in England / Europe, some 30 years ago. It can easly be proven wrong just by thought experiments, then the math and then the acutual analysis which he has done.
Please read the book I referenced in previous posts.
Well the "rinse and dump" method has certainly passed the test
Originally Posted by Photo Engineer
of time; at last look still an Ilford recommended way to wash.
Good job Mr. Mason.
BTW, the OP is from Australia. Dan
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The endpoint of all washing is the same: elimination of all put a trace amount of hypo.
No method produces a better result than another because all methods are run until the goal is achieved.
One can minimize either the expenditure of time or the expenditure of water. As a practical matter, as most people don't have laminar flow equipment:
- If time is of the essence then the better method is a continuous vigorous flow of water with some mechanical flexing of the material;
- If water conservation is more important then the better method is a series of agitated soakings.
Yes Dan, I know what conditions are like in OZ.
That is why I am trying my best to design a fixer that uses less water!
More on that sometime soon, but it has taken several years of work.
BTW, if Mason repudiates his work, what does that say about it? It works, just not well enough in some cases for archival work perhaps? I suggest that people "trust but verify". Do you? I check all prints for retained hypo and retained silver.
Thanks for all the suggestions. The Ilford washing sequence is quite what I'm looking for - efficient and environmentally friendly! I'll look into the other methods suggested too as well.
PE, is there any published work on wash time v water temperature
Most of the wash times I have seen refer to a 20C water stream.
Living in England my mean water temperature over the year is closer to 10C than 20C.
Therefore I "over wash" by a considerable margin, x2 at 15C water temp and x4 at 10C (BTW these are just my guesses at reasonable safety factors)
I don't know what film it is you are washing. If though
Originally Posted by Martin Aislabie
you can use something akin to the Ilford sequence then
room temperature washing is no problem. Keep a jug or
two of room temperature wash water at hand. Dan