THAT IN-LINE PROCESSOR.
Those Colchester Pearles - Major & Rita - are
regularly mentioned in this column, and I make no ologies
for this, indeed I am regularily indebted to them for
supplying copy, or ideas for copy, and usually at a time
when I am literally bereft of inspiration!
Like now, for instance, when an unusually bulky parcel
arrived containing American Magazines, tapes and written
notes which I will pass on from time to time for I am
sure there are interesting tit-bits and some valuable
advice to be passed on.
In my April column there was, for instance, a mere
mention of an in-line automatic processor for E6. Work on
this I`m assured, is proceeding - if not exactly apace -
with steady and studied progress! I have received a
sketch, from the Colchester "factory", of the
machine which gives an overall impression of the general
principles involved and I must admit to an overwhelming
admiration towards the ingenuity of the design team!
Briefly the design allows for eight tanks - one for each
solution and only two washes - and the differing times
needed in the various baths is governed by a clever
system of up and down travel but with more rollers in,
for instance, D1 tank than that for the reversal bath,
the film has a further distance to move... hense a longer
time in that bath.
Between baths there is a squeegee roller, to limit
contamination, and then the film ends up in a cleverly
contrived drying cabinet.
One cannot but admire the imaginative,
and even inspirational, orginality of this creation! I
just can`t wait for the "opening ceremony".
Which I am invited to perform... but remote control.
ooooOOOoooo
BLOW YOUR BLEACH!
There is nothing exeptional, apparently, about Ferric
EDTA (EDTA NaFe) bleaching agent, according to Robert
Chapman, writing in the American magazine, `Darkroom
Techniques`.
Ferric EDTA bleaches are not particularly fast or even
efficient. The chemical comprises an iron complex of
Ethylene-diamine, Tetra Acitic Acid. The EDTA prevents
the formation of ferrous hydroxide percipitate. Iron
bleaches can be made without using EDTA, or other similar
agents, but must be used at such low pH levels as to be
detrimental to colour materials. Ferricyanide, another
iron-based bleaching complex, has been written off by
many people as an enviromental hazard.
Ferric EDTA on the other hand has no, or very low,
toxicity and is acceptable enviromentally. The fact that
Ferric EDTA bleach is low acting explains why we use, in
the E6 process, particularly, a Conditioner Bath which
gives a helpful push, as it were, to the bleach.
One natural factor which keeps the Ferrous EDTA
concentration low is poor aeration. In the presence of
oxygen Ferrous EDTA automatically reverts to the active
Ferric EDTA form.
All of which goes to show the vital importance of
aerating the bleach before it goes into the developing
tank.
WHAT!! NO STOP BATH? Why, I have
often been asked, are stop bahs not included in modern
day reversal procedures? The short answers are that the
good old one-per-cent Acetic acid of former glory days
have been in effect, replaced by the Reversal and
Conditioner baths in the current E6 process.
These take over from the Acetic acid baths to perform
dual functions - to effectually to put an end to First
developer residue, in the case of the Clour Developer,
the change from a Ferricyanide Bleach to and EDTA NaFe
bleach.
For the Ferricyanide Bleach required all the help it
could get from the wash-out of the developer residue in
order to avoid stains due to contamination with the
Ferricyanide - whereas the Ferric EDTA doesn`t usually
exhibit this undesireable unwanted effect.
ooooOOOOoooo
RINSE IS BEST!
On a diplomatic note, however, a further logic reason for
the substitution of the rinse, rather than the Stop Bath,
following the First Developer is given in another article
by the same author. In this we are remined of the
formation of the colour film which has three, or more,
layers of emulsion.
With the E6 process it is actually intended that
developer activity tapers off gradually with a water
rinse rather than abruptly with a stop bath.
With a colour film having, as I`ve said, several layers
it will be obvious that developer activity will cease
first with the upper (yellow dye-forming layer), next
with the magenta dye-forming layer and finally with the
cyan dye-forming layer. So progressively longer First
Developing times from the upper to the lower layers are
built-in part of the E6 process.
Should a stop bath be used in place of the water rinse
more magenta and cyan hues would be formed during Colour
development ... giving a bluer balance. Sounds sense to
me!
ooooOOOOoooo
DID YOU KNOW?
That Tri-Sodium-Phosphate is a useful paint-brush
cleaner? In fact I hear it is on sale at hardware stores
under the obvious name of TSP.
ooooOOOOoooo
DID YOU KNOW?
That the denture cleaner, Den-Clen`, is an effective
cleaner for the plastic developing tank reels? It really
does remove the stains and is, additionally, very easy to
use with its handy locking cap which dispenses the fluid
economically through its built-in hard brush.
DID YOU KNOW? That the earliest
aerial photograph was taken in 1858 by Gaspard Felix
Tournachon from a ballon near Villadoucoubly on the
outskirts of Paris.
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