FROM WAY BACK WHEN!
(CRCN No. 4. Jan. 1 977)
The coming of the C.R.C. E6 formula has brought up the "should/shouldn`t we" wash between Bleach & Fixer and also
the need to `aerate` the EDTA Bleach. On reading through the past CRC Newsletters this seems to have been answered
way back in issue No. 4. in the Technical Section, on pages 2-3. While no credit is given, it would appear to have been
composed by the late and long missed, Will Griffiths. (Will produced the Swancolor Kit, (now, Lingcolour).WASHING FILMS.
Strictly speaking there is no need to wash any slide film between those two baths. Should the film be transferred directly
from the bleach solution to the fixer, without an intermediate rinse, the life of the fixer solution will be shortened. The fixer
will quickly `kill` any carried-over bleach solution. No stains will appear as a result of the direct transfer from the bleach
to the fixer. However, it is possible to rinse the film for a short period in order to prolong the life of the fixer solution. The
wash should be kept short, however, since prolonged washing will impair the removal of the silver salts by the fixer
solution, a little extra time should be allowed in the fixer bath to allow for this, should the film be washed between the
two baths.Washing of the film before the bleach is another story. Any traces of colour developing agents carried over to the bleach
solution will cause permanent and indelible stains in the slides.Due to the brevity of the washing in the E4 (& presumably likewise with E6) type process it is important to agitate the
film rather vigorously during the last half minute or so in the washes following the Stop Baths. The final wash must be
thorough enough to remove all traces of fixer chemicals from the emulsion. Failure to do so will affect the stability of the
cyan dye and may cause reddish stains in the slides.BLEACH/FIXING (BLIX).
The most suitable bleach chemical for the combined bath is the Ferric Sodium salt of Ethylenediaminetetra-acetic Acid.
This ferric salt is trivalent. During use the ferric salt is changed to the divalent ferrous salt. Before re-use this must be
re-converted to the trivalent ferric salt. This is easily done by aeration. The solution is simply poured into a bottle until it
is half full and then shaken vigorously for 15 seconds. It should not be stored in full bottles. (Today many members us a
fish-tank pump for this).The fixing salt most commonly specified for the combined bath is Ammonium Thiosulphate. This is the rapid fixing salt
and is not commonly available (not quite true today) in small quantities due to its instability. It can, however, be made
in situ by the addition of ammonium sulphate or ammonium chloride to ordinary sodium thiosulphate at the rate of 1 part
ammonium salt to 13 parts of sodium thiosulphate. Fixing time is then reduced by up to 50%. Other additions are
hardening agents such as potassium alum, or accelerators, such as sodium thiocyanate or potassium nitrate. The
accelerators assist in the removal of the silver salts from the baths.FERRICYANIDE BLEACH SOLUTION
There are two important points to observe with this solution. First, it should be remembered that a ferricyanide solution
can easily cause stains in the film. It is therefore important to adhere to the laid down formula for any particular film.
Remember that the stains may only appear long after the films have been processed, in some cases, months later.
Secondly, ferricyanide bleach baths should never be used at pH values below 5.00 as the ferricyanide ion becomes
unstable at pH values below 5.00. The colour dyes themselves may also become unstable at low pH values.FROM ISSUE No. 1. (April 1976)
From 1176 papers sent out, a return of some 625 votes favoured the widening of the Club (CR50) to all makes of the
new E4 films, which led to the change of name, to the C.R.C.
Following the result of the survey contained in the Special Issue of the National Newsletter (roughly 5-2 being in favour
of opening the Club to all makes of film), a Central Committee meeting was held on the 27th, March. The new
arrangements will apply after March 31st. 1976.SUBSCRIPTION The increased subscript- -ion of £2.50 is now due and members are urged to pay this amount as
soon as possible. (Just œ1, per member, went to the Area Leader, and that had to cover all expenses).£2.50!!, our present £5, due in April, represents a mere 50% in 17 years, not a bad deal, at all. I know Christmas has
just gone, and the New Year is but young, but please accept this as a timely reminder and think about getting your
1994/5 Subs payed in good time.
Thanks. Ed.