The Sustainable Darkroom
A Practical Guide to Environmentally Responsible Analogue Photography
Condensed from the 13-part Sustainable Darkroom blog series
Contents
- Introduction: The Hierarchy of Impact
- The Silver Problem
- Defensible Practice: What Actually Works
- Colour Processing: C-41 and RA-4
- Experimental Processes: Lith, Mordançage, Chromoskedasic
- Water Efficiency: The Wash Question
- Alternative Processes: Beyond Silver
- Upstream and End of Life
- Quick Reference Tables
- Checklists and Procedures
Chapter 1: Introduction
The Wrong Conversation
The sustainability discourse around analogue photography often focuses on developer choice: caffenol versus Rodinal, “natural” versus commercial, botanical versus synthetic. This focus is misguided.
After extensive research into photographic chemistry, toxicology data, and lifecycle impacts, a clear hierarchy emerges:
| Priority | Concern | Share of Impact |
|---|---|---|
| 1 | Silver in fixer | ~80% |
| 2 | Water consumption | ~10% |
| 3 | Specific hazardous chemistry | ~5% |
| 4 | Developer choice | ~2% |
| 5 | Packaging/consumables | ~2% |
| 6 | Energy | ~1% |
The implication is stark: addressing silver recovery eliminates approximately 80% of your darkroom's environmental impact. Everything else—including the developer debates that dominate online discussion—is refinement.
The 80% Rule
Silver is the dominant environmental concern in any silver-based photographic process. A single roll of 35mm film contains 0.5–2g of silver. This silver ends up dissolved in your fixer at concentrations of 3,000–8,000 mg/L.
For context: aquatic invertebrates die at 0.6 μg/L. Your spent fixer contains silver at concentrations roughly ten million times higher than lethal thresholds.
Without silver recovery, your darkroom releases persistent heavy metal contamination regardless of how “green” your developer is.
If you do nothing else from this guide: recover silver from your fixer.
Chapter 2: The Silver Problem
The Chemistry of Fixing
When you fix film or paper, thiosulfate ions form soluble complexes with silver:
AgBr + 2 S₂O₃²⁻ → [Ag(S₂O₃)₂]³⁻ + Br⁻
The silver doesn't vanish—it dissolves into your fixer, accumulating with every roll or print processed.
| Material | Silver Content | Silver to Fixer |
|---|---|---|
| 35mm B&W film (36 exp) | 0.5–1.5g | ~90% |
| 35mm colour film | 1–2g | 100% (bleached out) |
| 8×10 FB paper | 0.1–0.2g | ~60% |
| 8×10 RC paper | 0.05–0.1g | ~60% |
| 8×10 RA-4 colour | ~0.05g | 100% (bleached out) |
Why Silver Matters More Than Developer
The developer debate compares hydroquinone toxicity (LC₅₀ 0.044 mg/L for fish) to botanical alternatives. But consider actual concentrations in photographic waste:
| Solution | Toxicant | Concentration | LC₅₀ | Ratio |
|---|---|---|---|---|
| D-76 developer | Hydroquinone | ~2,000 mg/L | 0.044 mg/L | 45,000× |
| Spent fixer | Silver | ~5,000,000 μg/L | 0.6 μg/L | 8,000,000× |
Fixer's silver is roughly 180 times more hazardous relative to toxicity thresholds than developer's hydroquinone.
Additionally, hydroquinone biodegrades readily (70% in 14 days). Silver is an element—it persists indefinitely.
There Is No Green Fixer
The fixer isn't the problem. The silver in the fixer is the problem. And you can't avoid the silver—removing unexposed silver halides is the entire point of fixing.
Thiosulfate itself is benign (used to dechlorinate aquarium water). Alternative fixing agents (cyanide, thiocyanate, thiourea) are worse. There's no botanical fixer waiting to be discovered.
The only options:
- Recover the silver before discharge
- Dispose of fixer as hazardous waste
- Stop doing silver-gelatin photography
Chapter 3: Defensible Practice
Silver Recovery Methods
Method 1: Steel Wool Displacement (Recommended for Home Use)
Iron reduces silver ions to metallic silver:
2 Ag⁺ + Fe⁰ → 2 Ag⁰ + Fe²⁺
Procedure:
- Collect spent fixer in dedicated container
- Add fine steel wool (grade 0000)
- Leave outdoors (produces H₂S—rotten egg smell)
- Stir daily for 5–7 days
- Test for remaining silver
- Decant liquid (now drain-safe); retain silver sludge
Effectiveness: 95–99% silver removal Cost: Pennies per batch
Method 2: Electrolytic Recovery
Passes current through fixer to plate silver onto cathode. Produces high-purity silver (95–99.99%).
Best for: Community darkrooms processing >100L/month Cost: €500–2,000+ equipment
Method 3: Professional Collection
Collect spent fixer; arrange pickup by licensed waste handler or photo lab.
Best for: Low-volume users without space for DIY recovery
Two-Bath Fixing
Running two fixer baths in sequence extends capacity 4–10×:
- Film/prints enter first bath (older)—brief fix, accumulates silver
- Transfer to second bath (fresher)—ensures complete fixing
- When first bath exhausts: silver recovery, discard, promote second to first, make fresh second
Benefits:
- Dramatically reduced fixer consumption
- Archival quality (fresh second bath catches any residual)
- More efficient silver recovery (higher concentration in first bath)
Fixer Testing
Don't discard on schedule—test for exhaustion:
Hypo check solution: Add drops to fixer sample
- Clear/light yellow = good
- Milky precipitate = exhausted
Clearing time test: Time for film leader to clear
-
2× normal time = rotate baths
Chapter 4: Colour Processing
C-41 Film Development
C-41 adds concerns beyond B&W:
CD-4 Developer:
- Para-phenylenediamine derivative
- Skin sensitiser, suspected carcinogen (Category 2)
- H412: Harmful to aquatic organisms with long-lasting effects
Bleach (Ferric EDTA):
- EDTA is environmentally persistent
- Not readily biodegradable
Silver:
- Same concentrations as B&W (3,000–8,000 mg/L in blix)
- 100% of film silver becomes waste (bleached out completely)
Home vs. Lab Processing
| Factor | Home Processing | Lab Processing |
|---|---|---|
| Chemistry per roll | Higher (small batches) | Lower (replenishment) |
| Silver recovery | DIY or hazardous waste | Systematic/industrial |
| Failed batches | Possible (temperature drift) | Rare (automated) |
| Transport | None | Depends on distance |
Recommendation: For C-41, lab processing is often more sustainable than home processing—especially if you can't batch rolls together.
Kit Comparison
Blix-based kits (CineStill, some Tetenal): Convenient but complicate silver recovery (iron already present).
Separate bleach/fix (Bellini, Kodak Flexicolor): Fix behaves like B&W fixer—straightforward silver recovery.
RA-4 Colour Printing
Similar chemistry to C-41 but with different trade-offs:
Silver waste: 100% of paper silver goes to blix (vs. ~60% for B&W printing)
Efficiency factor: Drum processing uses ~10× less chemistry than tray processing
The Three Paths
| Path | Silver | Chemistry Efficiency | Recommendation |
|---|---|---|---|
| Home RA-4 (drum) | High concern | Low (small batches) | For process experience |
| Scan + inkjet | None | N/A | Eliminates silver entirely |
| Scan + commercial RA-4 | At scale with recovery | High (replenishment) | Often most sustainable |
Chapter 5: Experimental Processes
Lith Printing
Surprising finding: Lith printing is environmentally favourable compared to standard B&W printing.
Why: Extreme dilution (1+20 or more) means 30–40% less hydroquinone per print than standard MQ developers.
| Developer | Working Concentration | HQ per 8×10 Print |
|---|---|---|
| Standard MQ (1+9) | ~1.5 g/L hydroquinone | ~150mg |
| Lith (1+20) | ~1.0 g/L hydroquinone | ~100mg |
Fixer: Standard—same silver concerns and recovery methods apply.
Caveat: Irreproducibility may increase paper waste (lower hit rate for “perfect” prints).
Toning
| Toner | Toxicity | Disposal | Notes |
|---|---|---|---|
| Selenium | High | Hazardous waste | Replenish, don't discard; lasts years |
| Sepia/sulfide | Low | Drain-safe | Ventilate during use (H₂S) |
| Gold | Low | Hazardous (prudent) | Self-limiting due to cost |
| Iron blue | Very low | Drain-safe | Ferric compounds are benign |
Mordançage
The chemistry: Copper chloride bleach + glacial acetic acid + hydrogen peroxide
The problem: Copper is an aquatic toxin (EPA freshwater criterion: 2.3 μg/L). Working solution contains ~10g copper per litre—roughly 4 million times the criterion.
The mitigation: Mordançage bleach is reusable indefinitely. Top up with hydrogen peroxide as needed; copper cycles between oxidation states but isn't consumed.
Per-print burden: If you make 100 prints from one batch, copper-per-print is ~50mg. If you make 1,000, it's 5mg. The denominator grows; the numerator stays fixed.
Disposal: Eventually neutralise with NaOH (precipitates copper hydroxide), collect precipitate for hazardous waste.
Chromoskedasic Sabattier
Chemistry:
- Stabiliser: 15–20% ammonium thiocyanate (aquatic toxin, H411/H412)
- Activator: Potassium hydroxide solution
Critical distinction:
| Method | Chemistry per Session | Waste Generated | Sustainability |
|---|---|---|---|
| Tray immersion | 500ml–1L each | Significant sludge | Poor |
| Brush application | 40–60ml total (dilute) | Minimal (on prints) | Acceptable |
Recommendation: Brush application only. Tray method generates hazardous waste at unacceptable volumes.
Chapter 6: Water Efficiency
The Physics of Washing
Washing is diffusion-limited, not flow-limited. Thiosulfate ions diffuse from paper/film into surrounding water until equilibrium. Continuous flow is inefficient—you're diluting already-clean water.
Sequential water changes are more efficient: each fresh fill re-establishes the concentration gradient.
Film Washing: Ilford Method
| Step | Fill Tank | Inversions | Drain |
|---|---|---|---|
| 1 | Fresh water | 5 | Completely |
| 2 | Fresh water | 10 | Completely |
| 3 | Fresh water | 20 | Completely |
| 4 | Wetting agent | — | Done |
Total water: ~2 litres per roll Archival quality: Meets ISO 18917 standards
Print Washing
RC Paper
Resin coating prevents fixer absorption. Wash time: 30 seconds to 2 minutes maximum.
Do not overwash RC paper—extended washing causes edge penetration and curl.
Fibre Paper
Traditional method: 30–60 minutes running water = 40–60+ litres per session
HCA Method (Recommended):
- Rinse: 2–5 minutes
- Hypo Clearing Agent: 10 minutes with agitation
- Final wash: 3 tray changes, 2 minutes each
Total water: ~10–15 litres (70–80% reduction)
DIY Hypo Clearing Agent
Sodium sulfite 20–30g
Table salt 2–3 teaspoons (optional)
Water 1 litre
Cost: ~€0.10/litre vs. ~€0.50 commercial
Chapter 7: Alternative Processes
Sustainability Spectrum
| Process | Silver? | Toxic Chemistry | Overall |
|---|---|---|---|
| Cyanotype | No | None | ★★★★★ |
| Anthotype | No | None | ★★★★★ |
| Platinum/palladium | No | Low | ★★★★☆ |
| Van Dyke brown | Yes | Moderate | ★★★☆☆ |
| Kallitype | Yes | Moderate | ★★★☆☆ |
| Gum bichromate | No | HIGH | ★☆☆☆☆ |
Cyanotype: The Sustainable Benchmark
Chemistry: Ferric ammonium citrate + potassium ferricyanide
- Iron compounds used in food supplements
- Ferricyanide is NOT a cyanide hazard (cyanide groups tightly bound to iron)
- Processing: plain water only
- Waste: essentially harmless
If sustainability is your primary concern, cyanotype is the answer.
Gum Bichromate: The Warning
Dichromates (ammonium/potassium dichromate) are:
- Group 1 carcinogens (causes cancer in humans)
- Toxic to aquatic life
- Environmentally persistent
Requires: Gloves, ventilation, strict hazardous waste disposal
Chapter 8: Upstream and End of Life
Film Manufacturing
Film manufacturing has environmental costs we don't control:
- Silver mining (habitat disruption, energy, water)
- Gelatin production (animal byproduct, processing)
- Film base (cellulose triacetate or polyester)
- Chemical synthesis
What we can control:
- Expose thoughtfully (every wasted frame has manufacturing impact)
- Store properly (don't let film expire unused)
- Recover silver (returns it to the supply chain)
Creative Reuse Before Disposal
| Material | Condition | Reuse Options |
|---|---|---|
| Expired B&W film | Well-stored | Shoot with exposure compensation |
| Expired colour film | Colour shifts | Embrace the aesthetic |
| Fogged paper | Mild fog | Lith printing (fog disappears into shadows) |
| Fogged paper | Heavy fog | Lumen prints, chemigrams |
| Failed prints | Any | Mordançage, bleaching, collage |
| Clear negatives | Under/unfixed | Drawing substrates |
| Black negatives | Over/light leak | Bleach drawing, scratching |
Disposal Guide
| Chemistry | Disposal |
|---|---|
| Oxidised B&W developer | Drain (dilute) |
| Stop bath | Neutralise with bicarb, then drain |
| B&W fixer | Silver recovery → then drain |
| Colour developer | Hazardous waste |
| Colour bleach/blix | Hazardous waste (contains silver) |
| Selenium toner | Hazardous waste |
| Mordançage bleach | Neutralise, hazardous waste |
| Chromo solutions | Hazardous waste |
Chapter 9: Quick Reference Tables
The Hierarchy (Memorise This)
| Rank | Action | Impact |
|---|---|---|
| 1 | Silver recovery from fixer | ~80% |
| 2 | Efficient washing (HCA + sequential) | ~10% |
| 3 | Proper hazardous waste disposal | ~5% |
| 4 | Developer choice | ~2% |
Silver Content Reference
| Material | Silver Content |
|---|---|
| 35mm B&W (36 exp) | 0.5–1.5g |
| 35mm colour | 1–2g |
| 120 B&W | 1–2g |
| 120 colour | 1.5–2.5g |
| 8×10 FB paper | 0.1–0.2g |
| 8×10 RC paper | 0.05–0.1g |
| 8×10 RA-4 paper | ~0.05g |
Water Use Reference
| Process | Traditional | Efficient | Savings |
|---|---|---|---|
| Film wash (per roll) | 40+ L | 2 L | 95% |
| FB print wash (per session) | 50+ L | 10–15 L | 70–80% |
| RC print wash | 5–10 L | 3 L | 50% |
Process Sustainability Ratings
| Process | Rating | Key Concern |
|---|---|---|
| B&W film/print | ★★★★☆ | Silver (addressable) |
| Lith printing | ★★★★☆ | Silver; lower chemistry than standard |
| C-41 film | ★★★☆☆ | Silver + EDTA; consider lab |
| RA-4 printing | ★★☆☆☆ | Silver (100% to waste) |
| Selenium toning | ★★☆☆☆ | Heavy metal |
| Mordançage | ★★☆☆☆ | Copper (but reusable) |
| Chromo (brush) | ★★★☆☆ | Thiocyanate (small volume) |
| Chromo (tray) | ★☆☆☆☆ | Thiocyanate (large volume) |
| Cyanotype | ★★★★★ | None |
| Gum bichromate | ★☆☆☆☆ | Carcinogenic dichromate |
Chapter 10: Checklists and Procedures
Essential Practices Checklist
Non-negotiable:
- Silver recovery from ALL fixer
- Never pour fixer down drain
- Hazardous waste for: selenium, mordançage, chromo, colour chemistry
Recommended:
- Two-bath fixing system
- HCA for fibre print washing
- Ilford method for film washing
- Fixer testing (don't guess)
- Brush application for mordançage/chromo
Optional refinements:
- Bulk loading film
- Lab processing for C-41
- Reusing first rinse water
Steel Wool Silver Recovery Procedure
Materials: 5L container, fine steel wool (0000), outdoor location
Steps:
- Collect spent fixer until container full
- Add ~50g steel wool, loosely fluffed
- Place outdoors (H₂S smell)
- Stir daily for 5–7 days
- Test for remaining silver
- Decant liquid (drain-safe); collect sludge
- Accumulate sludge for eventual recycling/disposal
Two-Bath Fixing Rotation
When first bath tests exhausted:
1. Remove first bath
2. Silver recovery on first bath
3. Dispose of treated first bath
4. Move second bath → first position
5. Make fresh second bath
6. Update log
Ilford Film Wash
Fill → Invert 5× → Drain completely
Fill → Invert 10× → Drain completely
Fill → Invert 20× → Drain completely
Wetting agent rinse → Hang to dry
Total: ~2 litres, ~4 minutes
Fibre Print Wash (HCA Method)
1. Rinse: 2 tray changes (2 min)
2. HCA bath: 10 min with agitation
3. Wash: 3 tray fills, 2 min each
4. Dry
Total: ~10–15 litres, ~20 minutes
Conclusion: Proportionality, Not Perfection
Should You Feel Guilty?
No—if you're practicing responsibly.
The total environmental burden of a year of careful darkroom work:
- 50–100g silver (recovered)
- A few hundred litres of water
- Small quantities of organic compounds
- Occasional hazardous waste (properly disposed)
Compare to:
- One transatlantic flight: 1–2 tonnes CO₂
- One year of driving: 2–4 tonnes CO₂
- Digital photography: rare earth mining, e-waste, data centre energy
Darkroom photography, practiced responsibly, is a minor environmental activity.
Yes—if you're not thinking about it.
Pouring fixer down the drain while debating whether caffenol is greener than Rodinal is environmental theatre.
The Goal
Not perfection—proportionality.
Address the big things (silver, water). Be thoughtful about specific hazards (copper, selenium, thiocyanate). Don't waste energy on things that don't matter (developer brand, “natural” ingredients).
And continue making photographs. The darkroom tradition is worth preserving—and can be preserved responsibly.
Appendix: Key Data Sources
Silver toxicity: Nebeker et al., “Toxicity of silver to steelhead and rainbow trout, fathead minnows, and Daphnia magna,” Environmental Toxicology and Chemistry (1983)
Fixer silver content: US EPA, “RCRA in Focus: Photo Processing,” EPA 530-K-99-002 (1999)
Hydroquinone toxicity: ECHA Registration Dossier, European Chemicals Agency (2023)
Washing kinetics: Haist, Modern Photographic Processing (1979); Ilford Technical Information
Two-bath fixing: Anchell & Troop, The Film Developing Cookbook (1998)
Alternative processes: James, The Book of Alternative Photographic Processes (2015)
Sustainable Darkroom series ~34,000 words condensed to essential reference