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Twenty
AMERICAN CINEMATOGRAPHER
July. 1926
DESENSITIZERS
I Continued from Page 13)
The data in Table IV were obtained from curves similar to those in Fig. 9. These values merely indicate the variation in the effect on rate of development and fog with several developers.
Table IV
Effect of a Preliminary Bath in Pinakryptol Green on Fog and Time of Development with Various Developers.
Time in minutes
required to reach
the same image Fog for same
Developer. Pvro
density.
Soaked
in Desenwater. 'sitized. VA 4
3/2 m
2/2 3X
\oy4 ioy2
5/ 3-M
iyA 8/ 5/2 VA
image
Soaked in
water. 0.15 0.18
0.16
0.14
0.33
0.14 0.13
0.20
density.
Desensitized. 0.33
MQ-100* (Elon)..
MQ-80 (Elon 80%, H y d r o q u i none 20%)
0.19 0.21
MQ-25 (Elon 25%, H y d r o q u i none 75%)
0.24
MQ-O (Hydroquinone)
Chlorhydroquinone (MQ Formula)..
Caustic Glvcin
Rodinal
0.38
0.16 0.14 0.12
*MQ formula is: developing agent 5 grams, sodium sulphite 75 grams, sodium carbonate 25 grams, and potassium bromide 1.5 grams per liter.
Among these developers only rodinal showed a distinct decrease in fog on the desensitized film, while with glvcin and elon there was no appreciable change. It should perhaps be emphasized that 5 minutes treatment in a 1-10,000 solution is a longer time than is required in most cases for satisfactory desensitizing, but a shorter treatment would only diminish these effects and not eliminate them. Phenosafranine, which is generally stated to give no fog, was tested in the same way as the pinakryptol green with similar results. With pyro it gave bad fog, with MQ-100 no additional fog was produced, and in both cases development was retarded. It appears from the data obtained in these tests that the fog produced in a developer after desensitizing is closely related to the tendency of that developer to precipitate the dye. Possibly the precipitate formed in the emulsion has some sort of nucleating effect and so promotes the growth of fog.
5. Useful Life of a Desensitizing Bath.
The instructions furnished with pinakryptol green state that the solution should be kept in the dark, so it is probably light sensitive. However, solutions have been kept for severel weeks in an ordinary dark room in which a skylight was frequently open without noticeable decrease in strength.
The solutions of concentration 1-5000, 1-10,000, 1-25,000 and 1-50,000 used in tests previously described were also tested for exhaustion. Over a period of 10
3^i
GOERZ
Negative Raw Stock
Now
Key Numbered
MORE GRADATION; MORE DEFINITION; NO GRAIN
SOLE DISTRIBUTORS:
Fish-Schurman Corporation
45 West 45th Street New York City
1050 Cahuenga Avenue Hollywood, Cal.
IN CANADA:
JOHN A. CHANTLER & CO.
200 Bay Street, Toronto, Ont.
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Roy Davidge Film Laboratories
The Little Laboratory with the Big Reputation
6701 SANTA MONICA BLVD. HOLLYWOOD 1944
pict pyn tie
1/ALTER. J. VAN RpSSEM
6049 Hollywood Blvd. Phone Holly 725
Commercial Photography
Slill Developing and Prmtinr/* &HoicBCQraaas--flOR. RENT— Still
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