Cyanotype is often thought to end when the print is washed, dried, and hung on the wall. But what happens to the chemicals washed down the drain? Aindreas Scholz looks beyond the finished cyanotype to examine the washwater and waste. Through The Ecological Wetroom and a series of experiments, workshops and filtration tests, the project makes these usually overlooked by-products visible and asks how to become more aware of what it leaves behind. Rather than offering a final solution, the work proposes a way to observe, test, and learn.
What does waste reduction mean when a photographic process does not end with the finished image? Using The Ecological Wetroom as a practice-led case study, this article follows cyanotype washwater, filtration media and residues after printing. Rather than presenting a closed technical solution, it considers how collection, measurement, experimental filtration, retention and public learning can make photographic waste more visible, and where the limits of such interventions remain.
The photograph does not end at the print
A cyanotype can appear almost elemental. Paper is coated with an iron-salt sensitiser, placed in contact with a plant or other object, exposed to sunlight or ultraviolet light, and then washed in water. During washing, soluble unreacted sensitiser is removed, and the image is revealed, deepening towards Prussian blue as oxidation continues. The object is gone, the image remains, and the process can seem complete.
Yet, the finished print is only the most visible part of a larger material event. Water has been used. Chemistry has moved from the coated paper into the washing tray. Energy, tools, water, plants and extracted minerals have participated in the image. Coloured liquid remains, but it is often allowed to disappear into a drain and out of the photographer’s field of attention.
This research begins with that disappearance. It asks a simple question: what happens if the photographic process continues after the image appears, and the material by-products are kept within the photographer’s field of attention?
Rather than treating cyanotype washwater as an invisible by-product, I collect it in transparent vessels, observe and record it, pass it through an experimental layered DIY filter, and retain both the liquid and the used filter media for further study. Hydroponic plants and their exposed roots extend the experiment into a living environment that requires maintenance over time. The Ecological Wetroom is the installation through which I currently test these questions: part working photographic station, part provisional laboratory and part public-learning space.
From cyanotype history to a contemporary waste question
John Herschel described cyanotype in 1842 as a new photographic process based on the light sensitivity of iron salts (Herschel, 1842; Ware, 1999). A year later, Anna Atkins began issuing Photographs of British Algae: Cyanotype Impressions, placing botanical specimens in direct contact with sensitised paper to create detailed pale silhouettes against Prussian-blue grounds (Atkins, 1843–1853; New York Public Library, n.d.). The first instalment appeared in October 1843, and the project continued in parts and volumes until 1853.
Atkins’s book project is central to my practice. Her work brought together botany, classification, material experimentation and photographic publishing. My research returns to this history while shifting attention from the specimen represented in the image to the wider material conditions that make the image possible, and to what remains after the print has been washed.
My climate-adapted cyanotype practice challenges the treatment of water as a neutral or interchangeable resource. In selected stages of the process, I use responsibly gathered, site-responsive waters, including harvested rainwater and river water collected directly from the Thames, where collection and handling can be undertaken responsibly, rather than relying exclusively on distilled or deionised water. Dissolved minerals, contaminants and other site-specific characteristics of the water, together with local weather and environmental conditions, are therefore not merely subjects represented by the photograph; they participate materially in its formation.
Water is not a neutral support material. In cyanotype, washing removes water-soluble, unreacted sensitiser from the paper, while subsequent oxidation during wet processing and drying deepens the Prussian-blue image (Ware, 1999). The resulting washwater also carries dissolved and suspended residues away from the print.
The practical literature I have consulted commonly specifies how long a print should be washed but gives less attention to where the water originated, how much was used or what it contains afterwards. In my current research, the source and volume of water are therefore noted as part of the process rather than treated as incidental.
This does not mean that every local body of water should be collected or used. Access, permissions, ecological sensitivity, contamination and local guidance must all be considered. The aim is to replace the fiction of an abstract, limitless supply with a situated understanding of water as a shared and consequential material.
This shifts waste reduction away from the search for a single ‘green’ substitute and towards a sequence of practical questions: how much water is being used, what enters it, what can be collected, what can be measured, and what remains after any attempt at treatment?
Making waste visible
Collect the washwater → observe and record → filter experimentally → compare samples → retain and investigate the residues.
A first practical step is collection. When an exposed cyanotype is washed, the water is captured in a labelled tray rather than immediately discharged. This makes the colour, volume and changing appearance of the liquid available for observation. It also creates a record that can be compared with later samples.
From there, the captured washwater can be passed through a simple gravity-fed DIY filtration column built from accessible materials. Different prototypes have included gravel, coarse and fine sand, cotton, zeolite, chalk and activated charcoal. These materials are arranged in layers so that the washwater moves slowly through mineral, fibrous and carbon-based media.
The arrangement is experimental rather than prescriptive. It should not be copied as if it were a validated treatment specification. The materials, sequence, flow rate, water chemistry and degree of saturation all influence the outcome. Its value here is as a research structure through which material movement can be made visible, adjusted, compared and discussed.
After initial filtration, the washwater is passed repeatedly through the layered filtration media until it runs visibly clear. The number of filtration cycles varies according to the density and concentration of the cyanotype washwater being treated. Visual clarity is used here as an observational threshold rather than as evidence that all dissolved residues have been removed. Once this stage is reached, the water either enters a contained hydroponic element or is held alongside it for further observation, depending on the installation configuration. The plants are not presented as a decorative symbol of nature, nor as the sole filtering mechanism. Roots, water, light and continuing human care form part of a wider living environment in which liquids settle, roots extend, and residues accumulate over time.
The final stages are sampling and retention. Cyanotype washwater is compared before, during and after treatment, while used filtration materials are kept rather than discarded without examination. The process therefore does not end when the liquid appears clearer. The more important question is where the removed material may have gone.
What filtration can – and cannot – show
Preliminary ICP-OES analysis, a laboratory technique used to measure trace elements in liquid samples, conducted in collaboration with Technological University Dublin, examined samples taken before, during and after filtration over a nine-day period, including water from the hydroponic plant system containing filtered cyanotype washwater. The clearest direct comparison showed measurable iron decreasing from 366.849 ppb in untreated cyanotype washwater to 87.110 ppb after filtration, an approximate reduction of 76 per cent.
The wider sampling programme also examined water from experimental treatment vessels containing filtration media and plants. These results varied considerably over time, meaning the 76 per cent figure should be understood specifically as the difference between the untreated and filtered samples, rather than as evidence that the entire nine-day system, or plant activity alone, removed 76 per cent of the iron.
The finding is encouraging, but its limits are essential. It concerns measurable iron only; it is not evidence of a 76 per cent reduction in all pollutants, nor does it establish that the water is safe to drink, reuse or discharge. The system is not certified wastewater treatment, and visual clarity should not be confused with environmental safety.
Further repeated trials are needed to distinguish the effects of filtration, settling and plant activity and to test different cyanotype recipes, papers, water volumes and filter configurations. For a creative research project, this uncertainty is part of the work: the experiment places measurable change alongside what remains unknown and asks us to distinguish between visible improvement, analytical reduction, material transfer and verified environmental safety.
PRELIMINARY TEST RESULT
Measurable iron concentration: 366.849 ppb untreated → 87.110 ppb after treatment
Approximate reduction: 76%
The result is preliminary and does not demonstrate that the water is safe for discharge, reuse or consumption.
Filtration does not make waste disappear
In an early conversation about the project, Malin Fabbri raised a crucial question: what happens to the sand, cotton, charcoal, plants and other materials after they have been used?
A filter does not erase waste. It transfers and concentrates matter elsewhere. Iron-rich residues may remain in the sediment, fibres, charcoal, mineral layers, plant roots or containers. A liquid that appears clearer can therefore conceal a newly concentrated solid waste stream.
This problem has become central to the research. Used media are retained as part of an evolving material archive. Their staining, weight, texture and saturation record the process, while also demanding decisions about storage, testing and eventual disposal.
During fieldwork at a quarry producing building materials, I encountered examples of mineral and industrial residues being assessed for stabilisation and potential use as aggregate in construction products. This opened a further research question: might spent filtration media containing cyanotype residues eventually be tested for stabilisation within a building material, rather than simply discarded?
At present, this is only an exploratory proposition. It would require controlled material testing, environmental and toxicological assessment, and compliance with waste and construction regulations. It must not be presented as an established reuse route. Nevertheless, the question is valuable because it prevents the project from declaring success at the moment the water looks cleaner. Responsibility also means following the residue.
Waste reduction without claims of purity
I intentionally avoid describing this approach as fully sustainable or eco-friendly. Even the most carefully considered photographic process has a footprint. It depends upon mined and manufactured materials, paper production, transport, energy, water and labour. A claim of purity could simply push those dependencies out of sight.
The term ecological is more useful to me because it describes relationships rather than innocence. The process connects water, iron chemistry, contamination, plants, microorganisms, light, filters, tools, institutions and human attention. These participants do not contribute equally, and their relations are not automatically benign.
Donna Haraway’s call to ‘stay with the trouble’ offers a way of remaining with damaged and complicated worlds rather than seeking a clean technological escape (Haraway, 2016). María Puig de la Bellacasa’s account of care is also important here because care is not only a feeling or moral claim; it is material work that supports relations among human and more-than-human participants (Puig de la Bellacasa, 2017).
In practice, care appears as maintenance: collecting and labelling water, checking roots, replacing grow lights, documenting changes, retaining difficult residues and refusing to overstate a preliminary result. These activities are not secondary to waste reduction; they are the work required to understand where materials move and what remains.
Learning to see waste
The research becomes especially useful when it is activated with others. In workshops, participants make cyanotypes, but they also measure the water used, watch the image develop, collect the cyanotype washwater and construct small experimental filters from accessible media. They compare samples and discuss what appears to have changed, what can be measured and what remains unresolved.
This shifts the learning outcome. Participants do not leave only with a blueprint. They encounter the photograph as an event distributed across light, water, chemistry, plants, tools, waste and care, and notice material flows that are usually hidden once the image is finished.
Witnessing is central to the method. Learners see the sensitised paper change during exposure; observe Prussian blue deepen during washing; notice the colour and quantity of the used water; watch it move through the filter; and examine the stained materials that remain. Knowledge is produced through handling, questions, mistakes, repetition, sensory observation and discussion.
The photographer’s role also changes. Rather than presenting a perfected solution, I facilitate a shared investigation whose limits remain visible. Scientific language is introduced carefully, especially the difference between an apparent visual change, a measured analytical change and evidence that would be required to establish environmental safety.
This public dimension allows photographic history to meet contemporary responsibility. Atkins’s contact prints can be discussed alongside water use, chemical afterlives and residual waste. The 19th-century photographic process becomes a way to think collectively about how analogue photography might reduce waste without pretending that its material consequences can simply disappear.
A working question, not a finished answer
This approach is deliberately open-ended. Its value does not lie in claiming a universal filtration method, but in creating a structure through which photographers, scientists, horticulturists, educators, curators and communities can test questions about water use, waste, filtration and residue together.
Future stages will require repeated laboratory analysis, longer-term observation of plant and filter behaviour, more robust protocols for handling saturated media and deeper investigation into possible residue stabilisation. Each iteration can also respond to its location: its water sources, weather, plant life, institutional resources and local knowledge.
Photography often asks us to look at an image while forgetting the systems that produced it. This wetroom experiment reverses that emphasis. It keeps washwater, filters, roots, maintenance and residue within the frame of photographic practice for longer.
The research does not claim to solve the environmental consequences of analogue photography. It proposes something more modest and perhaps more demanding: that waste reduction begins with attention, measuring what is used, making by-products visible, refusing to confuse transfer with disappearance, and remaining responsible for materials after the photograph itself appears finished.
Waste reduction here is not a claim that waste disappears. It is a method for making material use, transfer and residue more visible.
References
Atkins, A. (1843–1853) Photographs of British Algae: Cyanotype Impressions. Halstead Place, Sevenoaks: privately published.
Haraway, D. J. (2016) Staying with the Trouble: Making Kin in the Chthulucene. Durham, NC: Duke University Press.
Herschel, J. F. W. (1842) ‘On the action of the rays of the solar spectrum on vegetable colours, and on some new photographic processes’, Philosophical Transactions of the Royal Society of London, 132, pp. 181–214. Available at: https://doi.org/10.1098/rstl.1842.0013.
New York Public Library (n.d.) Photographs of British algae: cyanotype impressions. NYPL Digital Collections. Available at: https://digitalcollections.nypl.org/collections/28d304b0-c612-012f-cd39-58d385a7bc34 (Accessed: 24 July 2026).
Puig de la Bellacasa, M. (2017) Matters of Care: Speculative Ethics in More Than Human Worlds. Minneapolis: University of Minnesota Press.
Scholz, A. (2026) The Ecological Wetroom™: preliminary ICP-OES analysis of cyanotype washwater. Unpublished research data produced in collaboration with Technological University Dublin.
Ware, M. (1999) Cyanotype: The History, Science and Art of Photographic Printing in Prussian Blue. London and Bradford: Science Museum and National Museum of Photography, Film & Television.
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Grüße Dich, Maren, and thank you so much for such a thoughtful response. Your project sounds fascinating too, particularly the connection between phytoremediation, plant-based colour and generating exposure energy through human power.
Yes, phytoremediation is very much part of what I am interested in with The Ecological Wetroom, especially the question of whether plants can do more than simply tolerate photographic residues and might actually help alter, absorb or immobilise some of what remains in the washwater.
One of the environmental chemists I have been working with also made a really important point to me: toxicity is far more complex than simply turning something “toxic” into something “non-toxic”. Even remediation and treatment require energy, materials and additional processes, which can create other environmental burdens elsewhere.
I increasingly think of this as a kind of wicked problem. We may reduce one form of pollution or toxicity, but in doing so we can end up shifting materials, energy use or waste into another part of the system rather than making them disappear altogether.
That is partly why I am interested in keeping the whole process visible, not claiming that the Wetroom somehow solves photographic pollution, but asking what happens to these materials, where they move, what they become, and what a more responsible photographic practice might look like when we acknowledge those complications.
Thank you again, I would be very interested to follow your phytoremediation research too.
Hi Melissa, thank you so much, I am really glad you find the research interesting.
As part of my PhD, I am able to work interdisciplinarily with environmental chemists, and they recommended using laboratory-based analysis because it is considered the most reliable way of measuring the iron remaining in the washwater and gives us quantifiable data that can be compared properly over time.
There may well be lower-tech ways of getting an indication of iron levels, but they would be less precise. It is a really good question though, especially in relation to making this kind of testing more accessible, so I will raise it with the environmental chemists at the next opportunity and see what they suggest.
And regarding my upcoming talks: at the moment it appears to be in-person events rather than online events.
Thanks again for asking.
hi Aindreas, i think your research is fascinting.
Is there a lo-teck way of measuring the iron salts left in the waste water, or does it have to be hi teck uni equipment.
Also is your upcoming talk on -line?
Thank you
Melissa
Grüße Dich Aindreas,
what an inspiring report, project and analysis coming from it! Thank you for sharing this open-process and encouraging all of us photographers to consider the environmental footstep of our practice as part of the outcome! Personally I have researched into a similar topic myself, producing cannabis plant-colors and trying to generate the energy for the exposure lights by transferring human-power to energy (simply by connecting a bike to a transformator). Zooming out a bit, my project also researched phytoremediation practices, which makes me curious if you have already looked into the plants feeding off the residue water and changing the chemical compounds of the waste into something that eventually can become non-tocix again? Will be following your work with great interest! Thank you!
Thank you, David. This is exactly the question my research is trying to explore.
Rather than assuming cyanotype washwater is either harmless or simply “waste”, I am interested in whether it can be treated as a potential resource within a more circular system, for example, filtered and reused to irrigate hydroponic plants, which may later themselves become botanical material for cyanotype.
The literature around cyanotype disposal is also not entirely consistent: some sources describe it as relatively low risk, while others raise concerns about impacts on aquatic environments. So for me, even reducing and reusing a small part of the process waste is a useful starting point for thinking more critically about photography’s material footprint.
I keep asking myself, why are you doing this? For example, is there a benefit to the environment – as opposed to having the water used in the cyanotype process enter my septic or for others, a sewer system?
I believe that the cyanotype process and it’s “waste water” are okay to dispose of in a septic or sewer system – which is not true for process water from silver b/w photography or other “alternatve processes” that use far more toxic chemistry. (I’ve at workshops were pieces were processed outside and the water “disposed of” into a lawn or the soil.)
As far as I can tell, you don’t really address the issue of how safe or environmentally “friendly” cyanotypes are, but perhaps are just expanding the creative process to include the “process water” that we usually just send somewhere else when it has served its purpose in our creative process. Or??? Again … I am curious, why? And is there a benefit?
Best, D