It should be mentioned that it would not be correct to vary the proportions of ether and alcohol very greatly, as an over proportion of alcohol would render the collodion weak and glutinous, and, being very soluble in water, would the sooner injure the silver solution. On the other hand too great a proportion of ether would make the collodion less sensitive.
NEGATIVE COLLODION. B.
| Alcohol and ether, equal parts. | |
| Anthony's Negative Cotton | 3 grains to ounce |
| Anthony's Climax Cotton | 1 |
Put the cotton into the ether and let it become saturated, then add the alcohol. Excite with p27
| Iodide of Ammonium | 3½ grains to ounce |
| Iodide of Cadmium | 2 |
| Bromide Cadmium | 2½ |
Collodion sometimes, from long keeping, loses sensitiveness and becomes of a deep red color. When such is the case, it should be set aside and fresh samples prepared, which would be improved in working quality by the addition of small quantities of the old, and thus old stock may be used up without deterioration in the work.
Negative collodion should not be so heavy bodied or thick as that for positives; neither should it be so highly excited. Good positive collodion should have as many as 8 grains of the iodides and bromides to the ounce, requiring a silver solution not lower than 50 grains strong and going somewhat higher in cold weather.
The standard silver solution for negatives is 45 grains of silver nitrate to the ounce of water and the collodion from 5½ to 6½ grains to the ounce, with a tendency to less in cold weather.
Collodion for negatives should be permitted to ripen a day or two before using, unless it is brought to that state by mixing with old.