The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

Home | About | Photography | Contact






Hydroquinone
thoroughly washing after being fixed, to dissolve out the slight precipitate of carbonate of lime deposited from the water. Numer-ous researches have been made on the subject of this reducing agent and more numerous still the formulae that have been recom-mended, one of the most complete papers was by Lainer, who summarises his experiments as follows : -
A Concentrated Rapid Hydroquinone Developer. A. Water............ ioo c.cm.
Sodium sulphite (cryst.) ... 25-30 grms.
Hydroquinone ... ... ... 10         ,,
Dissolve these by the aid of heat, and add to the solution 25 grms. of potassium ferrocyanide dissolved in 100 c.cm. of water.
B. - Dissolve 50 grms. of potassium hydrate in 100 c.cm. of water, or 30 grms. of sodium hydrate in 90 c.cm. of water.
For development, take 60 parts of A, 6 to 8 parts of the potash solution, and 40 parts of water ; the potash solution may be replaced by 10 parts of the solution of caustic soda. The two original solutions may be mixed, and should then be diluted with thrice its bulk of water.
Other Formulae.
1
2
3
4
5
A.
Water .........
600
900
950
1000
550 parts
Hydroquinone ...
10
10
10
10
10 ,,
Neutral sodium sulphite
25
40
30
35
35 n
Potassium ferrocyanide
-
120
90
25
25 M
B.
Potassium hydrate
5o
5o
-
5o
ยป>
Sodium hydrate
-
-
30
-
60 ..
Water .........
IOO
IOO
90
55o
550 H
Developer I. - 60 c.cm. of A and 3 c.cm. of B, brought out a sensitometer image in three-quarters of a minute to 240; but is apt to produce fog with some kinds of plates. The addition of about 12 per cent, of potassium ferrocyanide is found to have a very beneficial effect. Developer 2. - 60 c.cm. of A and 6 c.cm. of B permits exposures to be shortened, gives excellent details in the shadows, and allows very rapid development. Developer 3. - 60 c.cm. of A and 12 c.cm. of B gives negatives of a softer character than those given by Developer 2. . Developer 4 is a slower developer, 60 c.cm. of A being mixed with from 6 to 9 c.cm.
' 398