Anna Atkins’s Ghost and the Conception of the Combination Cyanotype
by: Ansel Oommen
If necessity is the mother of all invention, then sensibility must be the nanny. It has been my experience that the practical is often overlooked or omitted when discussing the creative process, as if ideas just arise willy nilly out of the blue.
Speaking of the color, I first encountered cyanotypes as an undergrad studying toxicology during the early spring of 2014. At the time, I was also an active member of the campus Earth Club, maintaining a childhood interest in all things botanical. As custom each spring, a small subset of members would water and monitor seedlings in the university greenhouse, before transplanting them outside in the garden.
The greenhouse sat hidden on the roof of St. Albert’s Hall, a building dedicated to academia via classroom and research laboratories. It was shared by the botany department and their many experiments of chimeric cacti cuttings and Arabidopsis knockouts. Unlike the rest of my peers, I had access to two sets of keys, one from Earth Club and the other from the botany lab of Dianella Howarth, PhD at St. John’s University. I was a frequent visitor of her lab, so much so, that her doctoral students gave me free reign of their facilities to conduct my own informal experiments.
Because of my major, I began to disown my juvenile mediums of ink and acrylic. After all, I didn’t need to be in a studio to use pen or paper. And besides, there were plenty of artists who worked with them, in capacities far greater than my own.
I did, however, need to be in a particular environment to find sodium hydroxide, formalin, or glacial acetic acid. Even more, I was privy to knowledge on how to use them safely. Having free access to new ingredients, I sought to diversify and colonize my own niche while simultaneously cross-pollinating from familiar sources.
My love for plants led to Google which in turn, led to Anna Atkins, who is widely considered to have been the first female photographer. Her 1843 book, Cyanotypes of British Algae, was mesmerizing and I was particularly thrilled to discover that the aesthetic cyanotype was chemical in nature. Fixed in a blue dream, lacy fronds seemed to be carefully teased apart to display every virtue of algae, a subject I had hardly thought noteworthy before. Tones of blue, especially in her print of Dictyota dichotoma, rested in each other as silhouettes — an element of depth I found lacking in most online searches.
Developed by Atkins’ friend and chemist, John Herschel, the cyanotype is an alternative photographic process that uses solutions of two iron salts: ferric ammonium citrate and potassium ferricyanide. Solutions are mixed in a 1:1 ratio, brushed onto a porous surface, and the newly sensitized surface is then stored in the dark to dry. Leaves or other objects can later be arranged on the citrine colored surface (this must be done in the dark to prevent autoexposure) and the whole print is then exposed to UV radiation, either from the sun or a UV lamp.
Through visual magic, UV triggers a photochemical reduction of ferric ammonium citrate from Fe(III) ions to Fe(II) ions. The Fe(II) ions then complex with potassium ferricyanide, producing ferric ferricyanide or Prussian blue, the water insoluble pigment responsible for the blueprint. Areas that are covered by the object are left unreacted since UV cannot pass through, leaving behind a negative image. These areas retain the original water soluble Fe(III) ions. Afterwards, the print is soaked in diluted acetic acid (household vinegar) and diluted hydrogen peroxide to wash away the unreacted Fe(III) ions and to further develop the rich cyan.
Fortunately, Dr. Howarth had both chemicals stocked in her lab. The experimentalist was eager to prepare the formulas from scratch rather than resorting to premade mixes. As I had assumed and later verified, chemistry is quite similar to baking, in that homemade is almost always better than store-bought.
The key issue was finding the right material: it had to resist tearing under prolonged moisture. The artist proposed the familiar watercolor paper and the scientist was keen to test it out. As hypothesized, watercolor did not tear. However, each brush load left its own graded tint, resulting in a splotchy, uneven distribution of citrine. Moreover, the paper began to warp towards the middle. Needless to say, I was unhappy.
On another visit to the lab, I began to ponder the merits of filter paper. Porous? Check. Water resistant? Check — after all, I had previously used it purify aspirin and strain out countless solutions. Economical? Check — one pack contained 100 filters and the lab had plenty of it. In fact, every school lab would have it. Ubiquitous and lowly like tissues or toilet rolls, filter paper came in circular discs of cotton cellulose. An upgraded cheesecloth, its only purpose was to remove impurities by separating solids from liquids, liquids from solids, or even solids from air. But the best part? Filter paper was thick and uniform. Because it was a lab item, it had to be vetted to separate liquids evenly during vacuum filtration, meaning it was perfect for absorbing them as well. I had found the ideal medium.
Now came the matter of finding fresh spring fare. Like a madman, I traipsed around campus with a pair of barber scissors, snipping every leaf, stem, and tendril that piqued my eye from oak leaf hydrangeas to Japanese maples to the bitter melon that I was growing for fun up in the greenhouse.
Due to its rooftop elevation, the greenhouse was the ideal locale for UV exposure. My initial experience was a success and in an instant, I grew more confident in my hybrid methodology. Yet, something continued to intrigue. In the aftermath, as I studied the prints, I noticed a peculiar phenomenon. Most of them were simple negatives revealing the outlines of white leaves and stems against an azure background — a traditional cyanotype akin to the ones I saw on the internet. But the mulberry print was different. It was almost a fossil of sorts, a primitive plant X-ray revealing the ghosts of a few veins. A long lost descendant of Atkins’ algae, it had somehow captured depth through multiple tones of blue.
Clearly, something had gone right. But what?
Unfortunately, I never had a chance to repeat the trial; in May of 2014, I graduated, walking away with a B.S. in Toxicology and 13 prints I considered more as preliminary research than artwork.
In the spring of 2016, I returned to school to pursue a professional license in medical technology. And once again, I found myself with access to a lab where I could experiment freely instead of testing building samples for asbestos or recording patient withdrawal behaviors. By this point, I had figured out a hypothesis. By virtue of spring, the mulberry leaves that I had picked were young and hadn’t fully developed their cuticle or waxy outer layer. They were also lighter in color, probably due to less chlorophyll content and other impeding plant pigments. As a result, some UV was able to pass through the leaf, and react with some of the underlying Fe(III) ions below. When those ions were reduced, they became Prussian blue. However, because the amount reacted underneath the leaf was nowhere near the amount reacted on the exposed portions of the paper, there was subtle variations in tonal values of Prussian blue — in effect, capturing the beauty of leaf architecture through controlled chemistry.
But there was another breakthrough. UV did not penetrate the leaf equally. Skeletal parts like the veins and petioles were denser, resolving as the lightest hues. Surely, there had to be a way to deliberately capture these tones, no matter the season.
Just like the proverbial apple falling on Newton’s head, I had reached my own epiphany through logic. The leaf has to be transparent.
I recalled another undergraduate experiment of mine which I had conducted at the laboratory of my former toxicology professor, Diane Hardej, PhD. Borrowing a technique from herpetologists and comparative anatomists, I had diaphonized a frog and two herring, rendering their tissues translucent through the digestive enzyme trypsin. I was certain there was a similar method for leaves. Sure enough, botanists had their own equivalent procedure.
It was as simple as putting two and two together. And so the concept of the combination cyanotype came into being. By chemically pre-treating the leaves, I render them translucent. In this new state, deprived of all their pigments, the leaves become a window for UV radiation which easily penetrates the tissue layers and reacts with the Fe(III) ions below. However, not all tissues are the same. The skeletal veins and petioles contain lignin, a very thick, rigid biopolymer. Like bones on an X-ray, these fortified tissues absorb more radiation than their softer, non-lignified counterparts. Since they absorb more, less UV passes through and fewer Fe(III) ions get reduced, so they appear highlighted.
Variations in species, leaf thickness, translucency, UV intensity, and exposure time are additional factors that account for the complex details that can be challenging to capture which are usually absent altogether from traditional prints.
Although 175 years have passed since its invention, the cyanotype has remained relatively untouched. Yet, there is still so much left to discover — as with all things in life.
My little misstep into alternative photography was an accident of my eclectic background. I am not a botanist at all, but I have done research at a botanical garden. I am not a chemist either, though I do hold a minor in chemistry. I have no formal training in art, yet I would like to think I create it. In this sense, neither professional nor amateur, both specialist and generalist, my condition mimicked the hodgepodge lives of early scientists and inventors. And so, I was able to channel that same inquisitive spirit that originally led Atkins to harness one discipline to unleash another.
As I continue tweaking the age old blueprint, I hope that my findings will be anything but [cyano] typical.
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