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Toning Cyanotypes

Because Prussian blue is nice but can get old


Maria Azul, variations of the same print with different toning baths



Cyanotypes are often many people’s getaway process into alternative photography, and they are easily recognisable by their characteristic cyan-blue tones… but do cyanotypes always have to be blue?


You can make the most out of your cyanotype kit and be surprised about the variety of colors you can produce from it using chemicals from your laundry room and even your kitchen’s organic waste.


Toning cyanotypes involves two main steps: bleaching, and toning.


Both processes can be done in dim light conditions.


Please note, that before starting this process it is advised to allow the cyanotype print to dry for about 24 hours.



BLEACHING


The purpose of bleaching is to “reduce” the blue iron color of the cyanotype in order to allow the toning to adhere. This requires submerging the print in a solution with a high pH.


There are different methods of bleaching, however, many photographers have pointed out that the main factor to consider is the composition of the water available.


However, several photographers point out that if the tap water is heavily chlorinated a bleaching solution might not be necessary.


Annette Golaz, author of “Cyanotype Toning; Using Botanicals to Tone Blueprints Naturally,” considers bleaching to be optional as well. Nonetheless, she points out that experimenting with different levels of bleaching allows for a wider color spectrum.


Another factor to consider is the “hardness” of water. “Hardness” in water refers to the calcium percentage in water. Golaz recommends bleaching “the print by immersing it face down in hard water,” and adding “0.5 mg of calcium carbonate per liter of warm water.” However, Golaz notes that “The softer the water, the longer it takes, since even by adding the calcium carbonate, you cannot shift the pH of soft water up to the same level as hard water.”


Other chemicals used for the bleaching solution are: sodium carbonate (soda ash, not to be mistaken with baking soda), detergent, and ammonia. However, it must be noted that ammonia has been reported to produce brown images.


How long does the cyanotype print must be left in the bleaching solution? This depends on the solution used, the density of the print, and the toner to be used. The duration of the bleaching bath ranges from 5 minutes to a few hours. According to Golaz this process “can take up to 24 hours, depending on the hardness of your tap water.”


In order to tell whether the bleaching process has been done successfully, the print will achieve an uniform golden yellow. At this point the print must be quickly rinsed with water to stop the bleaching process.



Cindy Dória, cyanotype toned with coffee



TONING


Coffee, borax, even carrots are used for toning cyanotypes. The one thing these ingredients have in common is tannin, or tannic acid. According to Encyclopedia Brittanica,


“[tannins] occur normally in the roots, wood, bark, leaves, and fruit of many plants, particularly in the bark of oak (Quercus) species and in sumac (Rhus) and myrobalan (Terminalia chebula) [...] Tannins are responsible for the astringency, colour, and some of the flavour in black and green teas.”


Tea and coffee, even red wine, are some of the most popular tannins for toning cyanotypes due to their availability and low cost. In order to tone the print, the toner has to be diluted in water, the ratio of water to toner will affect the final result. Likewise, the duration of the toning bath will depend on the toner and its concentration. For tea and coffee, when the print turns brown is a sign it is ready, and has been reported to take between 5 and 10 minutes.


Golaz shared one of her favorite botanical recipes using sweet potato peels in an interview with Alternative Photography:


“Place about 50 g of finely cut dried sweet potato peel and 0.5 g of calcium carbonate per 1000 ml of water in a stainless-steel pan. Bring tap water to the boil in a kettle, pour over the peel and leave to infuse for 15 minutes. Strain into a tray and let cool to 125o F. Place the cyanotype face down in the toner bath and leave for 2 to 3 hours.”


Once the toning bath is done, rinse the print and leave it out to dry out of direct light.



Jacquard has shared an interesting guide of how prints change when toned:




Whichever is your tannin of choice, we recommend having fun experimenting with cyanotype toning multiple variables.



Author: Ana Sofia Camarga


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