By
Frank White (Area 20)
It
has happened. Disaster! It failed to work, I have lost 2 films because
the Reversal Bath. Why? It is definitely the Reversal Reversal Bath. How
do I know! Well the leader usually 2 or 3 frames at the start of the
film was black and not clear. The last frame is Black, Black &
Black. The 1st. Developer had worked, because with the film at certain
angles images could be seen.Problem, What had gone wrong? Obviously an
investigation was called for! Solution weights and volumes had initially
been checked and were in accordance with the formula given in the latest
handbook.
A
phone call to Colin Powell (wrong number in the Handbook) didn`t
elucidate any real information. A phone call to Ron Croad "Well I
use it and don`t have any trouble", so does Rita Pearle. How do
they do it? They use a concentrated solution and dilute it, suggesting I
do the same. Bill Reid, the late Ron Knowles and Glyn Willicombe,
complained with myself of poor or not completion of Reversal why?
We
started our investigation by going back to Brian Wheatcroft`s
preliminary formula. Initially we are not concerned with quantities.
1st
Formula
2nd Formula
125 ml
500 ml
For use 1 part in 10
For use 1 part in 10
These formulae had lower quantities of Stannous Chloride.
3rd Formula
4th Formula
5th Formula
Ron Knowles
Bill Reid, Rita Pearle
Handbook (Yellow Cover)
P7 CRC Jan` 94 P.8.
CRC Oct` 95
300 ml
250 ml
250 ml
Ready for use.
Dilute 1 in 19 Dilute
1 in 9 for use
for use.
Notes on Stannous Chloride
Examination
of the formula, you will note:-
(a) Various dilutions.
(b) Various Weights of Stannous Chloride.
(c) The form of Stannous Chloride is not stated.
(d) Stannous Chloride exists as anhydrous Sn Cl2 M.W. 189.5 Stannous
Chloride also exists as a dehydrate. Sn Cl2 2H20 M.W. 225.
(e)
Stannous Chloride is moisture sensitive.
(f)
Corrosive and Toxic.
Let
us examine the concentration of Stannous Chloride in the Solutions. this
chemical being the fogging or chemical responsible for the fogging of
the film.
Since
the form is not stated ie. anhydrous or Crystal, there can be an error
i.e. if the crystal form is used, the weight should be increased in the
ratio of the M.W. 189.5 : 225 or 1.19. 2.
We
will now examine the quality of Stannous Chloride in the various
dilutions on the basis of 300 ml working solution.
1st
Formula
2nd Formula
3rd Formula
4th Formula
1
in 10 for use
1 in 10 for use
1 in 19 for use
1 in 9 for use
9ml - 90ml
9ml in 90ml
10ml - 190ml
30ml - 270ml = 300ml
.i.e.
27 - 270ml
ie 27 in 270ml
5ml - 95ml
wt of SnCl2 8.3 = 0.33
Total 297ml
Total 297ml
15ml in 300ml
wt of SnCl2=1.05
wt of SnCl2 4.2
wt of SnCl2 8.3
wt in 30ml = 0.99gms
÷
÷
÷
12.5
50
25
in 27ml = 0.08 x 2.7
in 27ml 0.08 x 2.7
in 15ml
= 0.22gms = 0.22gms
0.49 gms
In
the Standard formula the weight is given as 0.495gms the same as the
value given by Ron Knowles` formula, but double the weight is given by
Rita Pearle & Ron Croad`s concentrated formula. On top of which if
the initial formulation was based on anhydrous Stannous Chloride then
should the dihydrate form (Crystal) be used then the weight should be
increased to 0.6 gms for 300 ml of working solution.
REFERENCE
BRIAN WHEATCROFTS ORIGINAL FORMULATIONS
Formula 1.
Formula 2.
Acetic
Acid
6.0 mls
Acetic Acid
24.0 mls
Stannous Chloride
1.0 gms
Stannous Chloride 4.2 gms
P-aminophinol
0.5 mls
P-aminophenol
2.0 mls
EDTA (Na2)
3.75 gms
EDTA (Na2)
15.0 gms
Sod. Hydroxide 10%
25. mls
Sod. Hydroxide 10%
100. mls
Dilute 1 in 10 for use.
Dilute 1 in 10 for use.
From
the above, it becomes obvious why Ron Croad & Rita Pearle are not
having any trouble. Brian Wheatcroft was still experimenting, but his
work was never completed.
From
Glyn Willicombe`s work, although, iron may be suspected, I believe that
the real culprit is dissolved oxygen, for which the Stannous Chloride
has an affinity. In preparing the Reversal bath, the following
precaution should be taken, use Boiled water to drive out dissolved
oxygen, alternatives, distilled water, or liquid condensate from
freezers or refrigerators.
And
finally the quantity of Stannous Chloride should be increased to 0.99gms
in 300ml or 3.3gms/Litre of working solution. And the form of Stannous
Chloride should be stated as "Crystal".
Glyn
Willicombe (Area 20) makes these comments in response to Frank's
article:-
Bill,
you will certainly run into trouble (not necessarily the tobacco effect)
if you resume W&M 3.3 gms Stannous Chloride per litre and excess
quantities of other chemicals in the working solution of the reversal
bath.
The
correct figure is 1.65 gm. This is Kodak's figure..