Chromium intensifier for approximately proportional intensification of thin negatives whether arising from slight under-exposure or under-development.
| Ingredient | Quantity | |
|---|---|---|
| Potassium bichromate | 90 | grams |
| Hydrochloric acid | 64 | mililiters |
| Water to make | 1 | liter |
| Mix chemicals in order. | ||
Dilute 1:10. Harden the negative first in the formalin hardener. Bleach thoroughly at 18–21°C then wash until the yellow stain is removed (immersing the bleached and rinsed negative in a 5% solution of sodium carbonate for a few moments quickens this stage) and redevelop in artificial light or daylight (not direct sunlight) in any rapid non-staining developer which does not contain an excess of sulphite, such as Kodak Developer D72 diluted 1:3. The time of redevelopment varies from 3 to 10 minutes at 18–21°C depending on the degree of intensification desired. Then rinse and immerse in a fixing bath for 5 minutes and wash thoroughly.
Greater intensification can be secured by repeating the process. The degree of intensification can also be controlled by varying the time of redevelopment.
Note: Fine-grain developers of the borax type containing a high concentration of sulphite, such as Kodak Developer D76, are not suitable for re-development since the sulphite tends to dissolve the silver chloride before the developing agents have time to act on it.
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