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Writer's pictureAlternative Processes

Sustainable Cyanotype Practices: Bleaching with Ash and Toning with Botanicals

Did you know that you can bleach cyanotype prints using wood ash? I stumbled upon this fascinating method thanks to the sustainable darkroom. This technique not only connects us to historical practices but also offers a sustainable alternative to synthetic chemicals.

toning cyanotype with avocado peels

The Historical Use of Ash for Washing Clothes

My Italian grandmother often recounted how her mother washed clothes with ash during the war. The reason behind this practice lies in the alkaline nature of wood ash. When mixed with water, ash releases potassium carbonate and other alkaline compounds. These compounds increase the pH of the solution, creating an environment that effectively breaks down oils and stains in fabric, much like modern detergents.


The same alkaline properties that made ash an effective laundry aid also make it suitable for bleaching cyanotypes. Cyanotypes are traditionally blue prints created using a photosensitive solution applied to paper or fabric. The alkaline environment created by wood ash interacts with the iron compounds in the cyanotype, breaking them down and causing the blue color to fade.

Embrace sustainable cyanotype practices : How to Bleach Cyanotypes with Wood Ash

  1. Collect Ashes: After enjoying a barbecue with friends, allow the leftover ash to cool completely.

  2. Create Bleaching Solution: Mix a small pot of ash with 2 liters of water to form your bleaching solution.

  3. Bleach Your Prints: Submerge your cyanotype prints in the ash water solution. It may take up to 3 hours to bleach the prints completely. Note that the bleaching might be uneven without some agitation, potentially leaving darker stains.

bleaching cyanotype with wood ash

Toning Cyanotypes with Natural Botanicals

In addition to bleaching, toning cyanotypes can add unique hues to your prints. I experimented with sweet potato peels and avocado peels

Toning cyanotypes with botanical ingredients relies on the pigments present in these plants. Sweet potato peels and avocado skins contain various compounds that can alter the color of cyanotype prints.

  • Sweet Potato Peels: These peels are rich in beta-carotene and other carotenoids, which can impart a greenish-dark yellow hue to your prints.

  • Avocado Skins: Avocado skins contain anthocyanins and tannins, which produce a stunning Venetian red tone when used for toning.


toning cyanotype with avocado and sweet potato peels

The pigments in these natural ingredients interact with the iron compounds in cyanotype prints, resulting in a chemical reaction that alters the print's color. This method is not only effective but also environmentally friendly, avoiding the use of harsh synthetic chemicals.

How to Tone Cyanotypes with Botanicals


  1. Boil the Peels: Boil sweet potato peels and avocado peels separately for about 2.5 hours to extract the pigments.

  2. Prepare the Solutions: The boiling process will produce a greenish-dark yellow solution from the sweet potato peels and a Venetian red solution from the avocado skins.

  3. Tone the Prints: Submerge your bleached cyanotype prints in these baths for a few hours or overnight to achieve maximum saturation. While this extended soaking isn't necessary, it enhances the color intensity.



toning cyanotype with avocado and sweet potato

Embracing sustainable ingredients for cyanotype bleaching and toning not only reduces our environmental footprint but also reconnects us with traditional practices. By using wood ash and botanical extracts, we avoid harmful chemicals, promote recycling, and create unique, naturally toned prints.



​Butterfly wings print was toned with sweet potato 🍠
The other with avocado peel 🥑
toning cyanotype with avocado and sweet potato peels

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