A related question: Any thoughts on using non-tap water for washing? I'm thinking specifically of rain water collected in a barrel or the water collected from a dehumidifier? I know PE has advised against the latter for use in developers because of the presence of microorganisms and other contaminants, so I'm guessing the same water would be a poor choice for washing, but I'm not sure of that. Would using such water be OK if it were followed by a shortened wash using tap water? That would at least help reduce tap water consumption.
We must do everything possible to reduce the waste of water in our processes.....I am always amazed at the 'over washing' of RC prints, 60 to 90 seconds is all it needs, 2 mins if you are being ultra cautious.....
Simon ILFORD Photo / HARMAN technology Limited :
I've heard that dehumidifier water is bad bad bad. Because of the amount of bacteria and other little buggies that grow in it.
I use the Ilford wash method, modified on three counts. First, after the first wash, I give the film two minutes in a hypo clearing agent. I know you don't need to do this for film, but it can't hurt. Then I do agitation cycle, except I usually agitate more (20, 25, 30 instead of 5, 10, 15), and I let it sit for a 30 seconds or a minute after each agitation cycle. During this period I start cleaning up the bathroom a bit (wash funnels, etc.)
Seems to work so far (knock on wood).
"We must do everything possible to reduce the waste of water in our processes.....I am always amazed at the 'over washing' of RC prints, 60 to 90 seconds is all it needs, 2 mins if you are being ultra cautious....."
Since RC prints are a siver emulsion on a watrproof base and can be effectivly washed in a very short time, doesn't the same apply to film which is also a silver emulsion on a waterproof base???
I've been using 5 standing washes with frequent agitation over 15 minutes (while I'm doing clean-up) for the past 25+ years.
Now thaaaaaat oughta do it....
Does someone have a reference for the Ilford water change method? I can't find it on the Ilford site. Thanks!
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I've just looked in my copy of Monochrome Darkroom Practice by Jack Coote (1982), which has the following about film washing:
Now, without looking at the original material, I can't offer any advice about what excellent washing might be, but Coote goes on to mention that Levenson proposed that there be two levels of 'safe' washing - one for archival, and one for commercial use.
It is often mistakenly assumed that efficient washing can only be achieved by using large quantities of water for long periods of time. But, as G. I. P. Levenson has pointed out, it would be possible to wash 1000 feet of motion picture positive film to archival standard in one litre of water, provided that the water was used efficiently. He has also reported that: "Excellent washing of a processed roll-film was achieved in a spiral tank by giving just three half-minute changes of cold water and agitating well during each period. The tank was just emptied after each wash with no attempt to drain thoroughly. After the third wash, the film was wiped before hanging it up to dry."
As his target for adequate commercial
(my emphasis) washing of film, Levenson aimed at diluting one hundredfold the concentration of thiosulphate solution in the image layer when it left the fixer.
I've also just found This thread from APUG, where this site is referenced, which appears to go into some detail about the 'Ilford Wash'.
The FP4 datasheet states the Ilford way too - Page 5 of this PDF
Last edited by namke; 11-03-2008 at 02:59 PM. Click to view previous post history.
Reason: corrected second link; added link to FP4 datasheet
The Kodak Hypo test kit gives a standard reference in color and in quantity of retained hypo and silver halide in a coating for archival wash. Early Kodak manuals give in the range of 1 hour washing in running water to achieve this level for film and some FB papers.
I won't suggest that this is needed for modern papers or films, but I know this, that single wash baths are not efficient. Here is the reason:
Wash 1 can only remove 1/2 of the chemicals from the coating. This is a law of science shown by Mason.
Wash 2 can only remove 1/2 of the remainder using the same math.
Wash 3 can only remove 1/2 of #2.
And etc. You approach zero but never get there because the wash water you use never has zero chemistry in it. It always equillibrates with what was in the film from the past condition.
Now consider running water. It is always zero in chemistry and as it passes over the film, the exchange is roughly double that in single baths and it can get to zero in the film (or a very very tiny amount).
This latter wash can be quicker and more economical when done properly, but you must not overdo the wash.
Simon is right though. Today we must conserve our resources and this is why Ilford and Kodak both came up with the other method in hopes that it would conserve water, but misused it can result in underwashed photo materials. So, I suggest that in the final analysis, you use the silver halide retention test for rate of fixing, and the hypo retention test for rate of washing whatever method you choose for washing your film and prints.
And, don't chance it to water from rain or from dehumidifiers. Both of these contain atmospheric contaminants and bacteria that are not present in distilled or tap water.
PE-- I think you're only partially right about single wash baths because you're not taking into account the relative volumes of emulsion and the wash water. I've purified proteins and other materials using dialysis, and the concentrated side and the dilute side will reach an equilibrium when the concentrations are equal, *but* with a relatively larger volume of wash water--the initial concentration of the solute can easily drop to less than 5% with a single wash after the system reaches equilibrium. Imagine washing 1 ml of emulsion with 1 ml of water vs. washing with 1000 ml of water. If the washing bath is sufficiently large, it performs nearly as well as running water with no solute.
Here's a study of the Ilford wash method that you might like to read: