I’ve spent the past week and a half working to perfect both my basic cyanotype process and to re-explore the toning of cyanotypes in order to get colors other than the Prussian blue that is the native cyanotype hue.
If you are interested in the gory details of toning continue reading after the images. Otherwise you can stop here!
Cyanotype Toned with Tannic Acid and Ammonia
Cyanotype Toned with Tannic Acid and Sodium Carbonate
Cyanotype Toned with Tannic Acid and Ammonia
Cyanotype Toned with Tannic Acid and Sodium Carbonate
The first three prints are on platine (a paper designed for alternative processes such as cyanotype); the last image print is on Stonehenge Warm, a traditional printmaking paper. Note that the tone achieved with carbonate is influenced by the paper.
Here are the gory details…
Toning of cyanotypes involves two classes of chemicals, one needs a polyphenol and a base (alkali).
Tannic acid and gallic acid are commonly used pure polyphenols; coffee or tea are also sources of polyphenols and are sometimes used to tone cyanotypes.
The two most common bases used are sodium carbonate (washing soda) and ammonium hydroxide (common household ammonia).
If one looks at the literature, there are many, many different procedures people have devised to use these compounds to tone cyanotype.. Many of the descriptions talk about the variability in cyanotype toning and some even entourage one to embrace the serendipity and make one-of-a-kind, never to be reproduced singletons.
I guess that I am too much of a scientist, I want toning procedures that are repeatable and controllable. Thus, I have spent sometime experimenting to find a stable procedure.
My procedure, using prints that have dried overnight, is this:
- Re-wet the print for at least 2 minutes in water
- Soak in tannic acid* (2.5 g / 100 mL) for 5 minutes
- Rinse by dipping quickly in water (15-30 seconds)
- Place print in either sodium carbonate (7.5 g / mL) or ammonia (5 mL of household ammonia in 100 mL water) until desired tone is achieved; generally 30 – 90 seconds.
When one places the print in the base, the color quickly begins to change. I usually let the color change go to completion as I have found it difficult to stop the change in a reproducible manner; something to work on in the future. Sodium carbonate gives red-brown tones ending with a rich chocolate brown at completion. With ammonia one gets various shades of purple ending with an almost gray color at completion. In both cases the final shade achieved is influenced by a little by the paper used.
This procedure gives little if any bleaching of the image. In my view, this is a big plus. It basically eliminates the need to print the original cyanotype on the dark side and then hope that the result of bleaching (characteristic of many other procedures) is both pleasing and reproducible.
* I have done a few experiments using gallic acid as well but for the moment have concentrated on tannic acid. I have been using reagent grade tannic acid which is fairly expensive. I have ordered some food grade tannin, which is a reasonablly priced, but less pure for of tannic acid. We’ll have to see if it is an acceptable substitute.