Denis K
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- Joined
- Jun 24, 2009
- Messages
- 237
- Format
- 35mm
Ive heard the rule always fix your film for twice as long as it takes to clear quoted more often than I can recall, but have always wondered who it was first attributed to. Although I suspect this is not the first time it was quoted, I can at least trace it back to the year 1917. I was reading through an issue of Photo-Era magazine and came across the following reference which gives a good explanation of the rule and why it is so. Ill let it speak for itself. Can someone come up with an earlier reference?
From: Photo-Era Magazine
Volume: XXXIX No: 2
Date: August 1917
Article: Stains on Negatives and Prints (Their Cause and Their Cure)
Author: Not Attributed
(b) Incomplete Fixing. This can occur even with a new bath if the print or film is taken from the bath too soon. While the plate is fixing, the silver halide in the emulsion changes first to colorless silver thiosulphate, which is comparatively insoluble. At this point the milkiness of the plate or film disappears. By leaving the plate in the bath this soluble and colorless compound is changed to a more soluble double thiosulphate of silver, which can be easily washed out. When the film is removed from the fixing-bath immediately after the milkiness has disappeared the first stage of fixing no amount of washing, later, will remove the insoluble silver salt, and this will in time be changed to yellow silver sulphide stain. The only safe rule is the leave all prints and negatives in the fixing-bath for double the time required to reach the end of the first stage, which is marked by the disappearance of the milkiness.
(c) If prints or negatives have not been completely covered while in the fixing-bath, they may appear completely fixed; but in spots they may have fixed only as far as the first stage, with the result that on exposure to the air yellow stains will appear.
From: Photo-Era Magazine
Volume: XXXIX No: 2
Date: August 1917
Article: Stains on Negatives and Prints (Their Cause and Their Cure)
Author: Not Attributed
(b) Incomplete Fixing. This can occur even with a new bath if the print or film is taken from the bath too soon. While the plate is fixing, the silver halide in the emulsion changes first to colorless silver thiosulphate, which is comparatively insoluble. At this point the milkiness of the plate or film disappears. By leaving the plate in the bath this soluble and colorless compound is changed to a more soluble double thiosulphate of silver, which can be easily washed out. When the film is removed from the fixing-bath immediately after the milkiness has disappeared the first stage of fixing no amount of washing, later, will remove the insoluble silver salt, and this will in time be changed to yellow silver sulphide stain. The only safe rule is the leave all prints and negatives in the fixing-bath for double the time required to reach the end of the first stage, which is marked by the disappearance of the milkiness.
(c) If prints or negatives have not been completely covered while in the fixing-bath, they may appear completely fixed; but in spots they may have fixed only as far as the first stage, with the result that on exposure to the air yellow stains will appear.