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.
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 [p027]
Iodide of Ammonium 3-1/2 grains to ounce Iodide of Cadmium 2 " " " Bromide Cadmium 2-1/2 " " "
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 5-1/2 to 6-1/2 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.
Iodide Ammonium 192 grains Bromide Cadmium 128 " Bromide Potassium 96 " Ether and Alcohol 32 oz. each Cotton 320 grains
The preceding formulæ are for portrait work in studio. For other work, such as outdoor views, [p028] landscape or architectural, or for copying engravings, etc., certain modifications of the collodion, to produce greater intensity or more contrast, are desirable. Collodion suitable for such purposes can always be purchased from the photo stock dealer, in quantities desired, and for that reason it is not best for the amateur nor the professional photographer either, to prepare small samples for special purposes. If it should, however, be found at any time necessary to prepare such a collodion, the second formula of Negative Collodion A will be found suitable for views of buildings, copies of engravings and such like work.