The Caffenol Question: What Botanical Developers Actually Offer

Part 1 of 13 in the Sustainable Darkroom series | Next: Part 2 →

The first time I developed film in coffee, I felt like I was getting away with something. Instant coffee, vitamin C, washing soda—chemicals you could theoretically consume, though I wouldn't recommend it—mixed in a measuring jug and poured into a tank. The image that emerged was sharp, contrasty, with a grain structure reminiscent of Rodinal. It felt subversive: photography reduced to kitchen ingredients, industrial chemistry bypassed entirely.

That was three years ago. Since then, I've processed perhaps fifty rolls in various caffenol formulations, experimented with tea-based developers, and spent more time than I'd care to admit reading electrochemistry papers about polyphenol oxidation potentials. The romantic appeal hasn't entirely faded, but my understanding of what caffenol actually offers—and what it doesn't—has changed substantially.

The sustainability discourse around botanical developers tends toward the breathless. Coffee is natural! You can pour it down the drain! No scary industrial chemicals! These claims aren't false, exactly, but they're incomplete in ways that matter. And they often obscure what should be the central question: compared to what, and measured how?

This post examines what botanical developers actually offer from an environmental perspective—the genuine advantages, the hidden costs, and the uncomfortable reality that developer choice might be the wrong place to focus our sustainability efforts entirely.

The Chemistry Is Sound: Plants Really Do Develop Film

Let me start with what's unambiguously true: plant-derived compounds can reduce silver halides to metallic silver, and the chemistry explaining why is well-understood.

Photographic development requires a reducing agent—a molecule willing to donate electrons to exposed silver halide crystals, converting silver ions (Ag⁺) to metallic silver (Ag⁰). The structural requirement is an ortho-dihydroxy arrangement on an aromatic ring, commonly called a catechol moiety.¹ When oxidised in alkaline solution, these compounds lose two electrons and two protons, converting to quinones:

Catechol → Quinone + 2e⁻ + 2H⁺

This is precisely the mechanism by which hydroquinone, metol, and other synthetic developers work.¹ The difference is sourcing: hydroquinone is synthesised industrially, while plant polyphenols containing the same functional groups occur naturally in coffee, tea, wine, oak galls, and dozens of other botanical sources.

Electrochemistry research confirms this isn't folk chemistry. Peer-reviewed studies on silver nanoparticle synthesis demonstrate that tannic acid spontaneously reduces silver ions at room temperature—the same chemistry that occurs in your developing tank.² Caffeic acid, the actual developing agent in coffee (not caffeine, despite the name) exhibits pH-dependent oxidation³, which explains why botanical developers sometimes require strongly alkaline conditions (pH >10) to function effectively.

The active compounds map predictably to their plant sources:

• Gallic acid (3,4,5-trihydroxybenzoic acid): oak galls, tea, sumac, grape seeds
• Caffeic acid (3,4-dihydroxycinnamic acid): coffee, wine, many plants
• Catechins (flavan-3-ols with catechol groups): tea, particularly green tea
• Tannic acid (polygalloyl glucose ester): oak galls, tea, red wine
• Pyrogallol (1,2,3-trihydroxybenzene): derived from gallic acid via heating⁴

It's not surprising these compounds work—they're doing the same chemistry as synthetic developers, just with molecules assembled by plants rather than industrial processes.

The Toxicology Differential Is Real and Substantial

Here's where botanical developers genuinely shine: aquatic toxicity is dramatically lower than synthetic alternatives.

The OECD's SIDS assessment and ECHA registration dossiers provide standardised toxicity data.⁵ For hydroquinone—the workhorse of conventional MQ developers like D-76—the numbers are concerning:

• Fish LC₅₀ (96h): 0.044–0.638 mg/L ⁶
• Daphnia magna EC₅₀ (48h): 0.061–0.142 mg/L ⁶
• Algae NOEC: 0.0015 mg/L
• Classification: CLP Aquatic Acute 1, Aquatic Chronic 1

Compare this to tannic acid, a primary component of many botanical developers:

• Daphnia magna EC₅₀ (24h): 32–50 mg/L ⁷
• Periphyton LC₅₀: >1,000 mg/L

And ascorbic acid (vitamin C), used in caffenol and most botanical formulations:

• Zebrafish LC₅₀: 330.7 mg/L ⁸
• GRAS status (Generally Recognised As Safe)

The differential is stark. Tannic acid is approximately 350–800 times less acutely toxic than hydroquinone to Daphnia magna, a standard aquatic toxicity indicator. Ascorbic acid is effectively non-toxic at any concentration you'd encounter in darkroom waste. Pour spent caffenol down the drain and you're releasing compounds orders of magnitude safer than what's in your D-76.

This advantage is real. It's not marketing. It's not wishful thinking. If minimising acute aquatic toxicity were the sole criterion for sustainable developer choice, botanical options would win decisively.

But it's not the sole criterion.

The Hidden Costs: Coffee Production and Lifecycle Thinking

Here's where the sustainability case becomes complicated.

Caffenol's most common formulation uses instant coffee—typically 40 grams per litre of working solution. Where does that coffee come from? What environmental costs were incurred before it reached your darkroom?

Coffee is one of the world's most chemically intensive crops. Commodity production relies heavily on pesticides and fungicides. Processing requires substantial water: lifecycle assessments report median values of 3.6 kg CO₂ equivalent per kilogram of green coffee, with ranges spanning 0.15–14.5 kg CO₂ eq/kg depending on cultivation methods.⁹ Industrial ascorbic acid production generates wastewater with chemical oxygen demand values approaching 1.0 × 10⁶ mg/L—extraordinarily concentrated pollution at the manufacturing stage. Sodium carbonate production via the Solvay process releases CO₂ and generates calcium chloride waste.

None of this appears in the measuring jug when you mix your caffenol. The environmental costs are embedded, invisible, displaced to plantations in Colombia and chemical plants in China. The finished developer solution looks benign because the harm happened elsewhere.

Now, this critique applies to all photographic chemistry—synthetic developers have their own supply chain impacts. The question is whether caffenol's supply chain is actually better or worse than alternatives.

The honest answer: we don't know. As far as I can tell, no peer-reviewed lifecycle assessment compares botanical versus synthetic photographic developers. - the research simply doesn't exist (although please correct me if I'm wrong here!). We're comparing acute aquatic toxicity (where botanical developers excel) while ignoring production impacts, transportation, packaging, and end-of-life considerations (where the comparison is unclear).

One important exception: if you're making caffenol from spent coffee grounds—post-consumer waste collected from local cafés—the calculation genuinely changes. You're using material that would otherwise enter the waste stream, adding no new agricultural demand. The vitamin C and washing soda still carry embedded impacts, but the primary ingredient becomes effectively carbon-neutral. This is legitimate sustainability, not greenwashing.

But most caffenol practitioners aren't doing this. They're buying instant coffee, often in plastic packaging, often from industrial plantations. The romantic narrative of “kitchen chemistry” obscures commodity supply chains that aren't obviously better than industrial chemical synthesis.

Practical Limitations: Shelf Life and Reproducibility

Beyond environmental considerations, botanical developers carry practical costs that affect real-world sustainability.

Shelf life is the critical weakness. Working caffenol solutions must be used within 20–30 minutes due to rapid oxidation of ascorbic acid. The developer literally goes bad while you're using it—by the end of a development session, the chemistry has degraded measurably. Compare this to Rodinal, which has “virtually unlimited shelf life,” or D-76, which lasts months in a sealed bottle.

This matters environmentally. Short shelf life means:

• More frequent mixing (higher chemical consumption per roll)
• Difficulty batching multiple development sessions
• Wasted chemistry if your film jams or you need to pause
• No option for replenishment workflows

Some practitioners extend stability by adding sodium sulfite (50g/L) or freezing prepared solutions. The commercial product Cawanol Professional uses powdered format to sidestep the oxidation problem entirely. But standard caffenol remains use-immediately-or-lose-it chemistry.

Reproducibility requires unusual discipline. Plant phenol concentrations vary by growing conditions, harvest timing, variety, and storage. Instant coffee offers more consistent caffeic acid than brewed coffee because manufacturers standardise formulations, but variation persists. Experienced practitioners recommend:

• Using the same instant coffee brand consistently
• Measuring by weight rather than volume
• Monitoring pH (must exceed 10)
• Testing with expendable film before important work
• Adding iodised salt as restrainer for films above ISO 400

This isn't insurmountable—photographers have worked with variable materials for 180 years—but it represents friction that synthetic developers eliminate. Every failed development is wasted film, wasted chemistry, and wasted time. Inconsistency has environmental costs.

Historical Precedent: Photography Was Plant-Based First

One aspect of botanical developers that gets surprisingly little attention: photography's original developers were plant-derived.

Pyrogallol, the dominant developer throughout the wet collodion era, was first obtained in 1786 by Carl Wilhelm Scheele through heating gallic acid extracted from oak galls.¹⁰ Frederick Scott Archer demonstrated its photographic use in experiments from 1848–1850, publishing his wet collodion process in March 1851.¹¹ According to J. Towler's The Silver Sunbeam (1864), photographers could prepare pyrogallol themselves by fermenting nutgalls for three months to produce gallic acid, then heating it in oil under pressure.⁴

Gallic acid played a crucial role in William Henry Fox Talbot's 1840–1841 Calotype process—the first photographic development of a latent image.¹² Talbot's “exciting liquid” combined gallic acid with silver nitrate and acetic acid, reducing development time from one hour to one minute. The Bodleian Library's Talbot Catalogue Raisonné documents that Talbot physically cut the words “gallic acid” from his notebook to protect the secret.

Catechol was first isolated in 1839 from catechu, the boiled juice of Acacia catechu. Josef Maria Eder published on its photographic use in 1879.¹³

The shift to synthetic chemistry occurred between 1870 and 1900, driven by economics and reproducibility rather than chemistry limitations. Industrial synthesis offered purity, consistency, and cost efficiency at scale. But the underlying chemistry—catechol derivatives reducing silver halides—remained unchanged. Hydroquinone and metol do what gallic acid and pyrogallol did, just more predictably.

There's something poetic in returning to plant-based chemistry, connecting contemporary practice to photography's origins. Landscape photographer Roman Loranc photographs oak groves while using pyrogallol derived from oak galls, maintaining explicit continuity between subject and process. This isn't empty nostalgia—it's engagement with photography's material history.

But historical precedent doesn't automatically confer sustainability. The 19th century wasn't notably careful about environmental impact. Understanding that botanical developers have deep roots helps contextualise contemporary experiments; it doesn't settle the environmental question.

The Peer-Reviewed Evidence Gap

Perhaps the most uncomfortable finding from researching this post: the systematic scientific literature on botanical photographic developers barely exists.

The foundational academic work occurred at Rochester Institute of Technology in 1995, when Dr. Scott A. Williams’ Technical Photography class developed caffenol by testing coffee and tea as developers due to their phenolic acid content.¹⁴ This remains the most-cited academic origin point—and it's essentially a classroom experiment documented in DCCT magazine, not a peer-reviewed journal publication.

The Sustainable Darkroom collective, founded by London artist Hannah Fletcher in 2019, represents the most organised contemporary research effort.¹⁵ Their 2022 publication re·source compiles 198 pages of essays, recipes, and experiments from 44 practitioners worldwide. Tested botanical developers include lacto-fermented wild garlic, bladderwrack seaweed, and mint extracts. This is valuable documentation, but it's practitioner knowledge, not standardised sensitometric testing.

The most rigorous quantitative data comes from artist Andrés Pardo, whose 2018 residency at Mexico's LEC-Churubusco Studios produced gamma and density curves for hibiscus tea, nettle, and other herbal developers. His findings showed “strikingly similar tonal ranges and density” to standard cinematographic laboratory curves, with greater chemical fog in shadow regions. This represents rare empirical measurement—but it remains unpublished in imaging science journals.

What's missing:

• Sensitometric curves comparing botanical developers to D-76, Rodinal, HC-110 under controlled conditions
• Lifecycle assessments quantifying total environmental impact
• Long-term archival stability studies (do caffenol negatives last?)
• Standardised biodegradability testing for spent developer solutions
• Systematic comparison of silver recovery efficiency from different developer chemistries

The sustainability claims around botanical developers rest on acute toxicology data (solid), practitioner experience (extensive but unsystematised), and lifecycle assumptions (untested).

Beyond Chemistry: Material Unity

Having catalogued limitations, let me describe something that shifted my thinking about what botanical developers can offer—something that transcends environmental accounting entirely.

In August 2024, I attended a screening at The Silver Record festival in Vaasa. The performance was “Hypnos Theatre: Offering to the Spirits of Juniper” by Ellen Vikström and Henrik Sørlid, artists based in Tromsø working with Polar Film Lab.¹⁶

The 16mm film had been developed in juniper berry extract. During the projection, they burned juniper branches, filling the space with aromatic smoke. The images on screen—shot in the Norwegian/Sámi landscape where the juniper grew—emerged from chemistry derived from that same landscape.

Vikström's description captures something the sustainability discourse often misses:

Plant flesh slowly and purposefully penetrating mineral flesh, drawing out of it subterranean babies 3 years in the making—maturing and ripening with the revolving seasons—cycles of yellow, green and blue-black elixirs. The discipline of evergreen needles and the gentle protection of smoke.

The “3 years in the making” refers to juniper berries’ ripening cycle: green in the first year, blue-black by the third. The chemistry of development becomes inseparable from the biology of the plant, the seasonality of the landscape, the ceremonial burning during projection.

This isn't about toxicology comparisons or lifecycle assessments. It's about material unity—image, chemistry, subject, and presentation emerging from a single source. The film doesn't merely depict a landscape; it's made of that landscape, and the screening reintroduces the volatile compounds that the berries once held.

I mentioned earlier that Roman Loranc photographs oak groves using pyrogallol derived from oak galls. Vikström and Sørlid take this further: the material connection extends beyond processing into the screening itself, creating what they call a “cinematic ceremony.”

Whether this constitutes “sustainability” in any measurable sense is unclear—I have no data on juniper berry toxicology or the carbon footprint of ceremonial screenings in Finland. But it suggests that botanical developers might offer something orthogonal to the environmental debate: a way of making images that embeds the photographer in material relationships with specific places and organisms.

That's not nothing. It might even be more important than the toxicology.

So What Do Botanical Developers Actually Offer?

Having spent several thousand words complicating the picture, let me try to synthesise.

Genuine advantages:

• Dramatically lower acute aquatic toxicity (100–5,000× safer than hydroquinone)
• Drain-safe disposal in most jurisdictions
• Reduced handling hazards (no sensitisation risk, no carcinogen concerns)
• Distinctive aesthetic qualities unavailable from synthetic developers:
  • Tannin-based developers (tea, wine, oak gall) produce natural staining that enhances tonal separation and creates warmer image tones—similar to the revered pyrogallol “glow” but from food-safe compounds
  • Caffenol's characteristic high-acutance grain structure, often compared to Rodinal, with a distinctive midtone rendering
  • Natural toning effects: anthocyanins from berries shift image colour toward blue-violet; tannins warm highlights while preserving cool shadows, enabling split-tone effects without separate toning baths
  • Plant polyphenols can act as both developer and toner simultaneously, creating looks that would require multiple chemical steps with conventional processes
  • The variability that frustrates reproducibility can become an aesthetic resource—each batch slightly different, each print unique
• Connection to photographic history and material culture
• Potential for genuinely low-impact sourcing if using post-consumer waste

Genuine disadvantages:

• Short shelf life (caffenol) requiring immediate use
• Reproducibility challenges from variable source materials
• Embedded supply chain impacts (coffee production, vitamin C synthesis)
• Limited systematic documentation of archival properties
• No lifecycle assessment comparing total environmental impact

Unclear:

• Whether total lifecycle impact is better or worse than synthetic developers
• Long-term archival stability of botanically-developed negatives
• Optimal formulations for different film stocks
• Biodegradability in wastewater treatment systems

The honest conclusion is that botanical developers offer real but limited advantages, primarily around disposal toxicity, while carrying real but poorly quantified disadvantages around lifecycle impacts and practical handling. They're not a sustainability solution; they're one variable among many.

The Deeper Problem: Developer Might Not Matter

Here's where I have to introduce an uncomfortable idea that will occupy the next post in this series.

After spending months researching botanical developers, synthetic developers, toxicology data, and lifecycle thinking, I've come to believe we're having the wrong conversation. Developer choice is nearly irrelevant to the environmental impact of silver-gelatin photography.

Not because the chemistry doesn't matter—it does, somewhat—but because the magnitude of developer impacts is dwarfed by something else we rarely discuss: fixer.

When you develop film, your developer reduces exposed silver halides to metallic silver. That's the image. The developer is spent, relatively dilute, and contains no significant silver. It goes down the drain.

When you fix film, your fixer dissolves unexposed silver halides—and those silver ions accumulate in your fixer solution, reaching concentrations of 3,000–8,000 mg/L.¹⁷ Silver is acutely toxic to aquatic organisms at 0.6–5 μg/L.¹⁸ Your spent fixer contains silver at concentrations literally a million times higher than lethal thresholds.

One litre of spent fixer can contain enough silver to kill fish in a small stream. And there's no “green fixer” alternative—the silver is what you're removing. That's the whole point.

Choosing caffenol over Rodinal while pouring spent fixer down the drain is like debating whether the car should have chrome or steel bumpers while the engine's on fire. The developer matters; the fixer matters enormously more.

That's the subject of the next post.

---

References