Laboratoire des systèmes photoniques
École nationale supérieure de physique
Parc d'innovation, BP 10413, F-67412
Illkirch Cedex, France
There is certainly nothing wrong with the paper "Some
investigations on the kinematics of the Ilford film washing
procedure" by Rolf Suessbrich2.
The description of the emulsion washing as a diffusion process is
perfectly correct and experimental measurements are very
convincing. When it comes to quantitative calculation, however, a
complete estimation based on actual values should be done.
A 135/36 wet film holds about 4 ml of fixer solution, 2 ml of
which being absorbed inside the emulsion, the remaining located
at the surface of the film3. Drained, a 500 ml tank keeps about
6 ml of droplets along the walls and the cap4. Thus, there is a total of about 10 ml of
remaining fixer, which corresponds roughly to 600 mg of
If after pouring out the fixer we simply refill the tank with
500 ml of water and wait for the absorbed fixer to diffuse out of
the emulsion, we should end up with a residual thiosulfate level
of 1.2 g/l (600 mg:500 ml), which is just slightly below the
recommended archival limit of 1.5 g/l. Expressed in Suessbrich's units,
the residual hypo level in water as well as in film will be
"dil. 50" (10 ml:500 ml).
If the film is first thoroughly rinsed, the walls and the surface
of the film will be clean and only the 2 ml of absorbed fixer
will diffuse into the 500 ml filling water, lowering the residual
hypo level to 0.24 g/l or "dil. 250"6.
In any case, Suessbrich's conclusion remains true: a single wash is
theoretically sufficient. However, as he pointed it out, the time
required to complete the diffusion process may be excessive
because that process slows down as the hypo concentration
difference inside the emulsion and the surrounding water
decreases, thus preventing the reach of the equilibrium point.
Let us however carefully investigate the washing process and its
dynamic from Suessbrich's data. From his Fig. 2, where a good
wiping reduces the take over, it appears that after the first
wash, a second and a third washes have almost no effect (as have
no effect the additional washes of an already well washed film
- see Figs. 5 & 6). Additionally, it can be seen from the
shape of the curve that the first wash could be reduced up
One could object that having relatively clean water does not mean
that the emulsion is of the same cleanness. This is what
Suessbrich points out by claiming that the binding mechanism of
the hypo into the emulsion may prevent the reaching of the above
computed equilibrium points using a single wash. Indeed, breaking
that bindings may require a strong hypo concentration difference
between the emulsion and the surrounding water, which is achieved
by regularly replacing the used water by fresh one. But should
such a breaking occur in these successive baths, it would be
monitored by a significantly increase of hypo concentration in
water, which is, according to Fig. 2, not the case: the lower
curves show that only a minute quantity of thiosulfate migrates
out of the emulsion in the 2nd and the 3rd bath.
I would conclude, in a rather iconoclastic way, that a good
rinse and a single 1 minute wash in 500 ml of water with continuous
agitation will leave the films perfectly clean.
Of course I won't really advocate for archiving the films after
such a procedure, because there would be absolutely no safety
factor left: a 2- or 3-wash procedure is certainly a safer
figure. But this analysis embeds what Suessbrich suggests:
the washing requirements are usually largely
overestimated. In my lab, photographic films that were given no
more than a one minute rinse have been stored for more than ten
years without any degradation; the same is true for holographic
plates, whose silver grains are 1/100 000th smaller than those
of common B&W films and therefore much more prone to be
"eaten" by residual fixer7.
In my opinion the photographers community has developed over the
years a false but very obsessive position according to which a
proper washing cannot be achieved without leaving the film plenty
of time under a waterfall. And even the reasonable common
suggestion of washing the films for about a quarter of an hour
under a running flow which allows a complete change of water in
the tank every five minutes8 is a
waste of water compared to Ilford's method, because this
5' change rate requires a water flow of at least 1.5 l/min for a
500 ml tank9. It was a therefore a
pleasure to read Suessbrich's paper, which I hope will help to
break all these generally accepted but preconceived ideas about
3This was measured by
weighting the film dry, wet, and wet but wiped. It may sound
astonishing that a dry emulsion volume of 0.6 ml absorbs 2 ml of
liquid, but we should keep in mind that wet gelatin expands up to
10 times its dry thickness.
is a measured figure.
560 g/l hypo is a common figure for film
fixer at working strength.
because some hypo will diffuse out of the emulsion during the
7... and I remember having seen a well-washed film
turning yellow in two weeks because it was forgotten near a big
PVC roll whose chloride or solvent emanations quickly oxidize the silver
: I am pretty convinced that most of the encountered film
degradations comes from bad storage.
8Kodak washing procedure.
9We measured this by monitoring over time
the decrease in concentration of a conductivity tracer introduced
in the tank at the beginning of the wash.
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On 15 Feb 2005, 08:39.