An active developer formula for use on chloride contact papers to produce cold blue-black tones.

IngredientQuantity
Mix chemicals in order.
Metol
2.7
grams
Sodium sulfite anhydrous
40grams
Hydroquinone
10.5
grams
Sodium carbonate anhydrous
75
grams
Potassium bromide
0.8
grams
Water to make
1
liter

Dilute one part of stock solution with two parts of water and develop prints from 1.5–2.5 minutes at 20°C.