Going Beyond Blue to Explore Cyanotype Variables: Dilution, Exposure, and Moisture. Part 1

Want to go deep into experimental cyanotypes? In the first part of a 5-part series, Caroline Roberts shares her cyanotype research and how changes in chemical dilution and mixing ratios affect the tone and colour. Sharing the methods, discoveries, and visual results from her tests. In this experimental cyanotype series, Caroline Roberts explores how variations in dilution, exposure, and moisture can expand the creative potential of cyanotypes. Based on her research and studio practice, the series focuses on material and process-based experimentation beyond traditional methods.

Writer and photography / Caroline Roberts

Read the MSDS (Material Safety Data Sheet) before attempting to use chemicals and use the correct safety equipment.

In my article In the Footsteps of Herschel: A Cyanotype Artist’s Journey into the Archives I briefly mentioned my own research into extending the color range of the cyanotype. In this 5-part series, I’m going to go into that research in more detail, starting with my first attempts that cover the dilution and ratio of the two chemicals – Ferric Ammonium Citrate (Solution A) and Potassium Ferricyanide (Solution B).

I first encountered the cyanotype in March 2013. On a sunny morning, after a frustrating month in the studio, I pulled out a pack of sun print paper I had intended for my kids and started playing.

Simple plant photograms quickly gained water splashes and drips and so my love for the process was born – I was hooked on this magical way of recording and interacting with the world around me.

Once the pack of paper was gone, I bought pre-mixed chemistry and kept going. I was in an MFA program for Painting at the time, and my newfound obsession with an obscure photographic process wasn’t always appreciated. During a studio visit, I was told that I would “need to address the blue”. This comment set in motion an ongoing quest to create a wide range of colours with the cyanotype process.

The first dilution experiments occurred in September 2013, stemming from a parallel obsession with the tonal value exercise I was teaching in Beginning Painting. I wanted a way to control the tone of the final photogram since I was exposing outside in Texas, USA, where times are very short (6-8 minutes on a sunny day). At first, I kept the ratios of the two chemicals the same. Working from the ‘standard’ dilutions of 20g Ferric Ammonium Citrate / 100 ml for solution A and 8g of Potassium Ferricyanide/100ml for solution B, I would mix the solutions at a 1:1 ratio and then dilute the mixture to 75% (3 parts of mixture and 1 part of water). Then 50% strength and 25% strength, and so on.

Note that I refer to the 20g of Ferric Ammonium Citrate and 8g of Potassium Ferricyanide solutions as ‘standard’ because these are the dilutions of most pre-mixed formulations.

Being impatient, I rarely waited until my paper was dry before running outside with it. I noticed that the blues I got with these wet exposures leaned more towards teal than the dry exposures did. This splash image is a great example of that difference if you haven’t experienced it yourself.

I started experimenting with the ratio of the two chemicals, Ferric Ammonium Citrate and Potassium Ferricyanide, as well as their dilution. I mixed up base solutions (from dry chemistry), of the range 5g/100ml to 100g/100ml of Ferric Ammonium Citrate for solution A, and from 2g/100ml to 40g/100ml of Potassium Ferricyanide for solution B. Then I mixed the different dilutions in a systematic way to see what the effects of different ratios were. For example, 5g Ferric Ammonium Citrate/100ml solution A: 20g Potassium Ferricyanide/100ml B. Each combination was exposed for 4-6 hours in full sun using both dry and wet exposures.

The colour shifts between wet and dry exposures that are fairly subtle at regular dilutions become much more distinct when the ratio is altered. The very concentrated solutions gave crystal patterns in dry exposures, and a delicate and easily scratched surface for the wet exposures.

I’ve repeated these tests over a much wider range of dilutions, learning from the issues with concentrated solutions and experimenting with more dilution solutions and extreme ratios of the two chemicals. I found that even the extremes of ratios or dilutions give some kind of result.

Early in 2019, I started work on a project about climate change for which I wanted 8 different tones of blue on fabric panels. It was critical that these tones be produced consistently. Since I was exposing the big panels of fabric outside (from wet because I had no space to dry the 11ft/335cm long panels), the tones needed to come from the solution more than from the exposure time. However, the lightest two tones were from short exposure times, and the darkest tone had to come from coating and exposing the fabric a second time.

Want to experiment with this yourself? If you’re already a fan of the Wet Cyanotype, try testing the process with a wider range of A:B ratios. Even if you’re working from bottled solutions, it’s relatively easy to alter the ratio. For example, for a ratio of 5 parts A:1 part B use 50ml of solution A straight from the bottle, then dilute 10ml of solution B with 40ml of water to reach 50ml total. Then mix the 50ml of solution A with the 50ml of diluted solution B. Here are chemical calculators to help you if you want different ratios. Don’t forget to record your experiments – AlternativePhotography.com has a handy notebook for this!

The 5-part experimental cyanotype series

In this 5-part experimental cyanotype series, Caroline Roberts explores how variations in dilution, exposure, and moisture can expand the creative potential of cyanotypes. Based on her research and studio practice, the series focuses on material and process-based experimentation beyond traditional methods.

• Part #1 – Going Beyond Blue to Explore Cyanotype Variables: Dilution, Exposure, and Moisture – introduces her initial experiments – systematically varying wet, dry, and soaked paper conditions, as well as chemistry dilution and exposure settings – to establish a base for further testing.
• Part #2 – Working Wet: Techniques and Effects in Super-Wet Cyanotypes – explores what she calls the “super-wet” cyanotype: highly fluid chemistry used to create photograms with differing object weights and absorbency, but without adding other chemicals.
• Part #3 – Introducing Chemigraphs: Abstract Cyanotypes with Added Chemistry – focuses on chemigraphs – abstract works created by introducing reactive materials to the cyanotype mix, altering colour and texture during exposure and development.
• Part #4 – Combining Cyanotypes, Chemigraphs and Transparencies – details her process for combining dried chemigraph surfaces with simple transparency overlays, particularly text-based elements used in her publications Memoranda and Daybook.
• Part #5 – Cyanotype Layering: Chemigraphs Followed by Contact Prints – looks at combining these approaches – layering chemigraphs and transparency cyanotypes through multiple exposures and different coatings – to create complex, multi-process images.

This series is both a visual record and a technical resource for artists working with cyanotype, offering practical insights and encouraging further material investigation. To get notified when cyanotype articles are published, subscribe to the Cyanotype Newsletter.

Caroline Roberts, with a background in Chemical Engineering and an MFA in Painting, creates experimental, camera-less work exploring nature and climate. Her art has been widely exhibited and supported through residencies at BOX13, The Printing Museum, and Penland.