PROCESSING FORMULAE
The following chemical formulae are given to help those who wish to make up their own solutions. The warning should be made, however, that manufacturers' recommendations vary from time to time and it is a wise precaution to ascertain for any particular type of film, the current processing instructions issued.
Reversal Processing - suitable for Pathe S.S. Pan.
1. First Developer
| Avoir. |
Metric
|
|
| Sodium sulphite (anhydrous) | 2 ozs |
70 grams
|
| Hydroquinone | 176 grains |
10 grams
|
| Sodium carbonate (anhydrous) | 1 oz. 180 grains |
34 grams
|
| Potassium bromide | 141 grains |
8.8 grams
|
| Potassium thiocyanate | 53 grains |
3.4 grams
|
| Caustic soda | 88 grains |
5 grams
|
| Water to make | 40 ozs |
1 litre
|
The chemicals are to be dissolved in the order shown in one-half of the water at 125°F. Add the caustic soda last and make up to the full amount with cold water just before using.
Development time varies from 3 to 15 minutes at 65°F depending on the exposure received by the tilm. The best way to ascertain the correct development time is by processing short lengths of the film for varying times and selecting the most appropriate one by inspection of the results.
2. Bleach
| Potassium bichromate | 176 grains | 10 grams |
| Sulphuric acid (conc.) | 193 minims | 10 cc. |
| Water to make | 40 ozs | 1 litre |
Add the acid slowly to the solution of bichromate. Considerable heat may be developed locally, and it is advisable to stir the solution while the addition is being made.
3. Clear
| Sodium sulphite (anhydrous) | 2 ozs | 50 grams |
| Water to make | 40 ozs | 1 litre |
4 Second Developer
| Sodium sulphite (anhydrous) | 1 oz. 100 grains |
35 grams |
| Metol | 35 grains |
2.5 grams |
| Hydroquinone | 88 grains |
5 grams |
| Sodium carbonate (anhydrous) | 1 oz. 100 grains |
35 grams |
| Potassium bromide | 35 grains |
2.5 grams |
| Caustic soda | 40 grains |
2.8 grams |
| Water to make | 8 ozs |
200 cc |
Develop until film blackened throughout (4 to 5 minutes).
5. Fix
| Hypo | 1.5 ozs | 38 grams |
| Sodium bisulphite | 35 grains | 2.5 grams |
| Chrome alum | 35 grains | 2.5 grams |
| Water to make | 40 ozs | 1 litre |
Negative Developer
| Metol | 36 grains | 2 grams |
| Sodium sulphite (anhydrous) | 4 ozs | 100 grams |
| Hydroquinone | 88 grains | 5 grams |
| Borax | 36 grains | 2 grams |
| Water to make | 40 ozs | 1 litre |
Development will take from 7 to 15 minutes at 65°F, depending on the type of film and the degree of agitation received during processing.
To mako up the developer, use water at a temperature of about 125°F. Dissolve the metol in a small quantity (e.g. 8 ozs.) first, and then put in the Hydroquinone. Add to the sulphite and borax, already dissolved in the rest of the water.
Positive Developer
| Metol | 9 grains | 0.5 grams |
| Sodium sulphite (anhydrous) | 2 ozs | 50 grams |
| Hydroquinone | 88 grains | 5 grams |
| Sodium carbonate (anhydrous) | 1 oz | 25 grams |
| Potassium bromide | 27 grains | 1.5 grams |
| Water to make | 40 ozs | 1 litre |
Dissolve in the order shown, using water at about 125°F. Development will be complete in 3 to 5 minutes at 65°F depending on the degree of agitation received by the film during processing.
Intensification
1. Bleaching Solution
| Potassium bichromate | 35 grains | 2 grams |
| Hydrochloric acid | 40 minims | 2 cc. |
| Water to make | 40 ozs | 1 litre |
The film to be intensified should first be thoroughly washed before treatment in the bleaching solution. Treatment is complete (usually in about five minutes) when all of the black silver image has become yellowish-orange in colour.
2. Wash the bleached film thoroughly for 5 to 10 minutes, or at least for as long as it takes the clear areas of the film to become completely free from all traces of yellow stain.
3. Re-develop the film in a standard metol-hydroquinone developer, wash and dry.
The whole operation can be safely carried out in white light, but direct sun.light is ixladvisable.
Reduction
1. Reducing Solution
| Potassium ferricyanide | 130 grains | 7.5 grams |
| Water to make | 40 ozs | 1 litre |
As with intensifying, the film to be reduced must first be thoroughly washed before treatment in the reducing solution.
The length of treatment will vary from about one to five minutes, depending on the extent of reduction required, and it is advisable to make a test beforehand on a short piece of the film to be treated. Then transfer to:
2. Fixing Solution
| Hypo | 10 ozs | 250 grams |
| Water to make | 40 ozs | 1 litre |
Treatment in the fixing solution is complete within five minutes, after which the film should be thoroughly washed ! and dried.
The whole operation can be safely carried out in white light and if, at the end, the image is still too dark, it may be repeated from the start.
Toning
l. Bleaching solution
| Potassium ferricyanide | 1 oz. 260 grains | 20 grams |
| Water to make | 80 ozs | 1 litre |
2. After bleaching, the film is washed for five minutes (until all trace of the yellowish stain is gone from the highlights) and treated in one of the following baths, depending upon the colour desired.
3(a) Sepia
| Sodium sulphide | 350 grains | 10 grams |
| Sodium sulphite (anhydrous) | 175 grains | 5 grams |
| Water to make | 80 ozs. | 1 litre |
(b) Reddish-Brown
| Copper chloride | 4 ozs | 50 grams |
| Water to make | 80 ozs | 1 litre |
(c) Grass Green
| Iron perchloride | 1 oz. 260 grains | 20 grams |
| Potassium bromide | 350 grains | 10 grams |
| Oxalic acid | 350 grains | 10 grams |
| Water to make | 80 ozs | 1 litre |
Wash film thoroughly after toning. The iron-toned image is liable to attack by alkalis in ordinary tap water and should, therefore, be rinsed in changes of water made slightly acid by the addition of about 10 ccs. per litre of 10% hydrochloric acid or acetic acid.
