I recently started up making cyanotypes again after a hiatus of about twelve years.
Although I enjoy the Prussian blue of the native cyanotype, I also enjoy the variety of tones made available by further treating a cyanotype to alter its tone.
However, one of the things I was dissatisfied with in the past was the irreproducibility in the toning of cyanotypes. Thus, I have spent some time over the past few weeks working out a more stable procedure for toning cyanotypes.
To a chemist (I am a retired chemistry professor), the toning of cyanotypes involves the sequential exposure of the native print to solutions of two types of compounds, a polyphenol (typically tannic acid, gallic acid or pyrogallic acid) and an alkali (typically sodium carbonate or ammonium hydroxide). I have also started using sodium bicarbonate as the alkali as well. I am unaware of a prior report of use of bicarbonate in the toning of cyanotypes.
My procedure is simple and general in that one can pick and choose from the various components and obtain a variety of different tones using the same set of steps.
Here is the procedure:
I usually use print the have been “aged” a day or two to become fully oxidized and in this case, I soak the prints in water for a minimum of two minutes before starting.
1) Soak the print face down in a 2% (w/v) solution of polyphenol for 5 minutes with occasional rocking. The tone of the print will not change significantly at this stage.
2) Dip the print in a tray of water very briefly (10-15 seconds)
3) Place the print face down in an alkali solution (details below) and immediately turn the print face up. Rock the tray constantly and as soon as the desired tone is achieved transfer the print to a tray of water. The total time of exposure to alkali is 30-60 seconds; it should be just long enough to cause the change in tone. Longer times will result in more bleaching.
Sodium carbonate (washing soda) and sodium bicarbonate (baking soda) are used at 7.5% (w/v). The ammonium hydroxide solution is 5% (v/v) household ammonia in water.
4) Wash the print thoroughly before drying.
This procedure results in a mild bleaching of the print so I usually start with prints that are a bit on the dark side of acceptable.
There is also a bit of staining of the highlights with a resulting small loss of contrast. Pyrogallic acid seems to be the worse in this regard. Also, some papers stain more readily than others.
The results of some combinations of the various compounds are shown below:
Figure 1
Figure 2
Although I enjoy the Prussian blue of the native cyanotype, I also enjoy the variety of tones made available by further treating a cyanotype to alter its tone.
However, one of the things I was dissatisfied with in the past was the irreproducibility in the toning of cyanotypes. Thus, I have spent some time over the past few weeks working out a more stable procedure for toning cyanotypes.
To a chemist (I am a retired chemistry professor), the toning of cyanotypes involves the sequential exposure of the native print to solutions of two types of compounds, a polyphenol (typically tannic acid, gallic acid or pyrogallic acid) and an alkali (typically sodium carbonate or ammonium hydroxide). I have also started using sodium bicarbonate as the alkali as well. I am unaware of a prior report of use of bicarbonate in the toning of cyanotypes.
My procedure is simple and general in that one can pick and choose from the various components and obtain a variety of different tones using the same set of steps.
Here is the procedure:
I usually use print the have been “aged” a day or two to become fully oxidized and in this case, I soak the prints in water for a minimum of two minutes before starting.
1) Soak the print face down in a 2% (w/v) solution of polyphenol for 5 minutes with occasional rocking. The tone of the print will not change significantly at this stage.
2) Dip the print in a tray of water very briefly (10-15 seconds)
3) Place the print face down in an alkali solution (details below) and immediately turn the print face up. Rock the tray constantly and as soon as the desired tone is achieved transfer the print to a tray of water. The total time of exposure to alkali is 30-60 seconds; it should be just long enough to cause the change in tone. Longer times will result in more bleaching.
Sodium carbonate (washing soda) and sodium bicarbonate (baking soda) are used at 7.5% (w/v). The ammonium hydroxide solution is 5% (v/v) household ammonia in water.
4) Wash the print thoroughly before drying.
This procedure results in a mild bleaching of the print so I usually start with prints that are a bit on the dark side of acceptable.
There is also a bit of staining of the highlights with a resulting small loss of contrast. Pyrogallic acid seems to be the worse in this regard. Also, some papers stain more readily than others.
The results of some combinations of the various compounds are shown below:
Figure 1
Figure 2