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How to bleach a cyanotype print

Bleaching is perhaps the most direct and straightforward method of altering the colour of your cyanotype print. It’s simple to do and is something I quite recommend trying if you are dabbling in the world of cyanotype - there a several possibilities for its use, and it can also act as a base for further processes, like toning. Bleaching can be applied to an entire print to turn the print yellow, or as it is not an instant process, it is also possible to remove the print part way through the bleaching process and create a partial bleach affect. Alternatively, the bleaching solution may also be applied with a paintbrush to only partially bleach a section.

A white wall with several framed cyanotype prints, in various tones of blue and yellow.

Bleaching can be achieved with several different household chemicals, and the method outlined below is one of the most popular, using sodium carbonate (also known as soda ash or washing soda) as the bleaching agent. Other household bleaches may be used, such as ammonia or chlorine bleach, however I don’t recommend these as they require more careful handling, smell bad, and in the case of chlorine bleach, they can damage the paper too.

Getting Started

Things you need

  • 2 plastic trays, each big enough for your print to lay flat in. Old plastic tubs or clean meat or produce trays are good options, and it’s best to use a tray that is a bit bigger than your print, and one that you are not intending to use later for food storage.
  • Cold water.
  • Sodium carbonate. This is a white powder alternatively know as soda ash or washing soda – in Australia it can be found at Woolworths or Coles under the name “Lectric Inwash & Soaker Washing Soda 1kg”.
  • Cyanotype prints: you can use either the original blue prints, or prints you have already toned (bleached or unbleached). It's generally recommended that you use prints that are already dry and at least a day old. 

How much bleaching solution to make

This depends on your print size and if your are intending to bleach the entire print or just paint it on. If you are using one of my A6 or A5 cyanotype kits and want to bleach the whole print, I would suggest a minimum of 250ml and 500ml of bleaching solution respectively, though this is dependent on how large a tray you are using. It’s important that the tray has enough solution in it so that the print will float freely, without resting on the bottom of the tray - I suggest filling it to at least 1 cm of depth.

In general, and as the solution is quick and cheap to make, I make about 1 liter at a time and bleach several prints one after another. I like to use the ratio of 1-2 tsp of sodium carbonate per 1 litre of water.  As a rule of thumb, you will know the solution is too strong if the print turns bright purple on immersion.

Step by step bleaching instructions

  1. Prepare two trays. Fill one tray with plain water (for rinsing).
  2. To make the bleaching solution, measure your desired amount of cold water into the second tray, and add the sodium carbonate power required using the ratio listed above.
  3. Stir the bleaching solution well until the the grains are completely dissolved (remaining grains can cause uneven bleaching).
  4. Immerse you cyanotype print in the bleach bath. As with toning, you can have it floating face up or down. If it’s face up, agitate the solution regularly so that dry spots don’t appear on the paper. If it’s face down, check to make sure that air bubbles are not trapped underneath – these can cause spots of unbleached print.
  5. Watch carefully as the print begins to bleach. You will notice that it will go through a few different shades of blue before turning yellow, as well as probably fading unevenly. Feel free to remove the print anytime you like the result - this may be when it is fully bleached or at some point earlier.
  6. As soon as you are happy with the result, remove the print to the plain water bath for rinsing. Leave for 5-10 minutes to insure the bleach is removed.
  7. Rinse a final time in fresh water and leave to dry.

A note on timing

I sometimes find that the bleaching process takes me quite a bit longer than expected, and this is often on prints which are older or have been exposed  longer. Some may take 5 minutes to bleach, some may take up to an hour to get rid of all the blue tones. On occasion I have found that particularly stubborn blue tones become more diminished with a long soak in fresh water after being removed from the bleaching bath.

Different ways to bleach

The images above each display a different way of applying bleach for a different affect on your blue cyanotype print. 

  1. This print is fully bleached, and has turned a nice lemon yellow tone. This tone can only be achieved from a print that has been exposed long enough to make quite a dark blue - darker blues correspond to darker yellows, lighter blues become paler, almost beige tones.
  2. This denim blue print was immersed in the bleaching solution for only a short time, just enough to tone the blue down. In the top corners and bottom of the print you can see where the emulsion layer was likely thinner, as these areas have bleached the most.
  3. The beige and greyish-blue tones here were achieved by removing the the print from the bleach bath when it was mostly, but not fully bleached.
  4. This print was exposed to make a mid blue colour, then later wetted with plain water and scattered with grains of the sodium carbonate. As each grain dissolves on the wet surface, it quickly bleaches the paper beneath. The results of this technique vary depending on how wet the paper is, and how quickly the paper is washed afterwards.
  5. In this example, the bleaching solution was painted on with a brush in squiggly lines across the print. The bleach has no effect on white areas of the print, but can subtly alter the color wherever it is applied.