How to tone a cyanotype – the process
Place the three trays next to each other and pour one liter of demineralized water into each.
Starting from the left, dissolve a teaspoon of Sodium Carbonate in the first, leave simple demineralized water in the second and dissolve two tablespoons of tannic acid in the third on your right.
At this point the toning procedure can begin.
First, we proceed to moisten our Cyanotype in demineralized water. There is no definite time, the important thing is that the print returns to wet as before the final drying, after the washing at the end of the printing process.
Drain well the print and immerse it with the emulsion upwards in the Sodium Carbonate.
The print will begin to color magenta and lose definition in the highlights. There is no defined time for this phase and you will have to decide when to stop washing (also called “bleaching phase”). It usually doesn’t last more than 30 seconds.
After the 30 seconds of bleaching you will have to immerse the print again in the demieralized water to stop the chemical reaction with the Sodium Carbonate and, at the same time, for avoid to contaminate the Tannic Acid bath.
Leave the print for 30-60 seconds in water and then dip the print in the Tannic Acid.
The Tannic Acid bath can last several hours, depending on the colour you want to obtain.