| Metol | 16 | grams |
| Hydrochinon | 16 | grams |
| Sodium sulphite | 60 | grams |
| Sodium hydroxide | 10 | grams |
| Potassium bromide | 10 | grams |
| Water to | 1 | litre |
To keep the ingredients in solution in cold weather, 50 c.c. of alcohol should be included in every litre of solution. All things considered this is probably the most practical and satisfactory developer for aerial negatives.
Developers for Papers.—The following formula has been found very satisfactory for papers:
| Metol | .9 | gram |
| Hydrochinon | 3.6 | gram |
| Sodium carbonate | 20.0 | gram |
| Sodium sulphite | 14.0 | gram |
| Potassium bromide | .5 to 1.0 | gram |
| Water to | 1 | litre |
Fixing Baths.—For plates the following fixing and hardening bath is recommended:
| Sodium thiosulphate (hypo) | 350 | grams |
| Potassium chrome alum | 6 | grams |
| Sodium bisulphite | 10 | grams |
| Water to | 1000 | c.c. |
During hot weather, the above quantities of chrome alum and bisulphite are doubled.
For papers the following:
| Hypo, 35 per cent. | 100 | volumes |
| Acid hardener | 5 | volumes |
The acid hardener is constituted as follows: