Redevelopment obviates the difficulty from varied results caused by halide composition and type (i.e. chloride, bromide, chlorobromide, or iodochlorobromide) of the silver halide emulsion by reducing all halide compositions to a common denominator before selecting a particular toning developer. The silver metal image is first converted to silver bromide using a classic ferricyanide bleach. The redeveloper then converts the siver bromide to a disirable print tone.
CHEMICAL SAFETY
All chemicals are dangerous and must be treated with respect. Please read the warning on each package. There is one chemical that needs special attention: catechol (pyrocatechin).
Catechol has a high vapor pressure and it is a phenol. The high vapor pressure means that the solid catechol evaporates readily. When you open a bottle of catechol, you can smell it. Always store solid catechol in a tightly capped glass container. When mixing a solution containing catechol, work in a well ventilated area. When catechol is a solution its vapor pressure is not a problem.
The fact that catechol is a phenol means that it is a corrosive and has the potential to cause skin burns. If you should spill a solution of catechol, wash the area (or skin) with soap and water. Use tongs or rubber gloves whenever possible.
Rehologenating Bleach
| Chemical | Amount | Units |
|---|---|---|
| Water | 750 | ml |
| Potassium Ferricyanide | 8 | g |
| Potassium Bromide | 12 | g |
| Water to make | 1000 | ml |
Redeveloper
| Chemical | Amount | Units |
|---|---|---|
| Water | 750 | ml |
| Catechol | 2 | g |
| Sodium carbonate (mono) | 10 | g |
| Water to make | 1000 | ml |
USAGE
The Warm-Tone Redevelopment will usually darken the shadow areas and lighten the highlights of the print.
REFERENCE
Warm-Tone Redeveloper,
Photographic Processes, Robert Chapman, p.57