The Colour Print Question: RA-4 and Its Alternatives

Part 5 of 13 in the Sustainable Darkroom series | ← Previous: Part 4 | Next: Part 6 →

I do both RA-4 colour printing and scanning with digital output. The RA-4 work happens in a rotary drum processor with Adox chemistry and Fuji paper; the digital path runs through a scanner and an inkjet printer. Each has its satisfactions and frustrations. But which is actually more sustainable?

This post examines RA-4 printing specifically, then compares it with the digital alternative. There's also a question that came up during research that deserves attention: if you're printing black-and-white images, is RA-4 onto colour paper more sustainable than traditional B&W printing?

What's in RA-4 Chemistry?

RA-4 is to colour printing what C-41 is to colour film development: a standardised process using specific chemistry that must interact with the paper's integral dye couplers.¹

The Developer

RA-4 developer contains CD-3 (4-amino-N-ethyl-N-(β-methanesulfonamidoethyl)-m-toluidine), a colour developing agent closely related to C-41's CD-4. The same concerns apply:

• Skin sensitisation: CD-3 can cause allergic reactions with repeated exposure. The Adox RA-4 kit I use carries hazard statements H317 (“May cause allergic skin reaction”) and H412 (“Harmful to aquatic organisms with long lasting effects”).²
• PPD-class chemistry: Like CD-4, CD-3 is a para-phenylenediamine derivative with associated toxicity concerns.

RA-4 developer operates at lower temperature than C-41 (35°C versus 38°C) and is somewhat more forgiving of temperature variation, though still tighter than B&W processing.

The Blix

RA-4 uses a combined bleach-fix (blix) almost universally—separate bleach and fix is rare in colour print processing. The blix contains:

• Ferric ammonium EDTA: Bleaches the developed silver image back to silver halide
• Ammonium thiosulfate: Dissolves the silver halide

The silver from colour prints ends up in the blix, just as it does in C-41 processing. Colour paper has lower silver content than film per unit area, but print making typically involves much more total chemistry than film development—especially if you're making multiple prints or test strips.

The Stabiliser Question

Traditional RA-4 included a stabiliser bath containing formaldehyde, which cross-linked the dyes and extended print life.³ Modern colour papers have stabilisers built into the emulsion layers, and most contemporary RA-4 kits (including the Adox chemistry I use) either omit the stabiliser entirely or use a formaldehyde-free final rinse.

This is genuine environmental progress—formaldehyde is a known carcinogen and respiratory irritant. If you're using RA-4 chemistry from the past decade, you're likely not encountering it.

Rotary Drum Processing: The Efficiency Argument

I process RA-4 in a rotary drum (Jobo-style), which has significant implications for sustainability:

Chemistry use: Drum processing uses far less chemistry per print than tray processing. A typical 8×10 print requires about 70–100ml of each solution in a drum, versus 1–2 litres for adequate tray coverage. Over a printing session, this difference compounds dramatically.

Temperature control: Rotary processors maintain temperature through water baths, reducing the energy needed compared to heating open trays. The enclosed drum also reduces oxidation and evaporation.

Silver concentration: Because less chemistry is used per print, the chemistry exhausts faster—silver accumulates more rapidly per litre. This means smaller volumes of more concentrated waste, which is actually preferable for silver recovery.

The trade-off is equipment cost and complexity. Tray processing requires essentially no equipment beyond the trays; rotary processing requires a drum and some form of roller base or processor.

RA-4 for Black-and-White Images?

This question arose during research: if you're making black-and-white prints, is RA-4 onto colour paper more sustainable than traditional silver gelatin printing?

First, let's look at the silver content of each paper type. This matters because it determines how much silver ends up in your waste chemistry.

Silver Coating Densities

Based on available data:⁴

Black-and-white papers:

• Typical range: 1–4 g/m² silver
• RC papers (like Ilford Multigrade RC): toward the lower end (~1.5–2 g/m²)
• Fibre-based papers: toward the higher end (2–4 g/m²)
• The higher silver content in premium papers contributes to their richer tonal range and deeper blacks

Colour RA-4 papers:

• Typical range: ~1 g/m² silver or less
• Modern colour papers have been engineered for thinner image-forming layers
• Less silver is needed because the final image is dye-based, not silver-based

So B&W papers actually contain more silver per unit area than colour papers—sometimes 2–4 times as much.

But Here's the Catch

The key difference isn't coating weight—it's what happens to the silver during processing:

RA-4 processing: All the silver from the paper becomes waste. The silver catalyses dye formation, then is bleached and fixed out. 100% of that ~1 g/m² ends up in your blix.

B&W processing: Only the unexposed silver goes to the fixer. The image-forming silver stays in the print. For a typical print with, say, 40% average density, roughly 40% of the silver remains in the image and 60% goes to fixer.

So for an 8×10 print (0.05 m²):

Paper Type	Silver in paper	Silver to waste	Silver retained
RA-4 colour (~1 g/m²)	50mg	50mg (100%)	0mg
Ilford MG RC (~1.5 g/m²)	75mg	~45mg (60%)	~30mg
Ilford FB (~2.5 g/m²)	125mg	~75mg (60%)	~50mg

The maths is closer than I initially thought. RA-4's lower silver coating partially compensates for the fact that it all becomes waste. For RC papers specifically, the difference is modest—perhaps 10–20% less silver waste with B&W.

For fibre-based B&W papers, the higher coating weight means more total silver, but also more retained in the print. The waste percentage is similar to RA-4 in absolute terms, but you end up with a silver-rich archival object rather than a dye print.

Conclusion: For RC papers, B&W is marginally more sustainable in terms of silver waste. The bigger differences are in developer chemistry (CD-3 vs. hydroquinone) and the EDTA in RA-4 blix. For FB papers, the calculation becomes more complex because you're comparing very different objects.

The Digital Alternative

The obvious comparison is scanning your colour negatives and printing digitally. But there's also a middle path I use: scanning at home and sending files to a commercial RA-4 printer. Let me examine all three options.

Pure Wet Darkroom (Home RA-4)

This is what I do with my rotary drum, Adox chemistry, and Fuji paper. Full analogue chain from negative to print.

Scan + Inkjet (Home Digital)

Scanning itself has minimal environmental impact—electricity to run the scanner, and that's about it. No chemistry, no consumables beyond the occasional cleaning supplies.

Digital printing (inkjet or pigment) introduces:

• Ink cartridges (plastic, mixed materials, difficult to recycle)
• Paper (embedded production impacts, but no silver)
• Energy use for printer and computer
• Replacement printheads and maintenance

Scan + Commercial RA-4 Printer

This is my hybrid approach for much of my colour work: I scan negatives at home, then send digital files to a lab with a commercial RA-4 printer (machines like the Fuji Frontier or Noritsu that expose RA-4 paper with lasers or LEDs from digital files).

Why this might be more sustainable:

Commercial RA-4 printers operate at industrial scale with replenishment systems. A minilab running continuously uses far less chemistry per print than my home drum processor with its small-batch, discard-after-session workflow.

Labs processing hundreds or thousands of prints per day achieve chemistry efficiency that's impossible at home volumes. The silver recovery is also typically more systematic—commercial operations often use electrolytic recovery or metallic replacement cartridges.

Temperature control is automated and precise. No wasted chemistry from temperature drift or failed sessions.

The trade-offs:

You lose the full analogue chain. The negative is digitised, which may or may not matter to you aesthetically.

Transport emissions exist (though for a lab in walking distance, these are minimal).

You have no control over the lab's actual environmental practices. They might be exemplary; they might not.

Comparing All Three Paths

Aspect	Home RA-4	Scan + Inkjet	Scan + Commercial RA-4
Heavy metals	Silver in blix (high concern)	None	Silver (but at scale with recovery)
Persistent chemicals	EDTA, CD-3 derivatives	Ink chemistry varies	Same as home RA-4, but diluted by volume
Energy	Temperature control	Printer + computer	Commercial facility (amortised)
Chemistry efficiency	Low (small batches)	N/A	High (replenishment systems)
Silver recovery	DIY or hazardous waste	N/A	Typically systematic
Per-print cost	Higher (chemistry + paper)	Lower (after equipment)	Moderate
Image permanence	Dye-based, ~60–100 years	Pigment: >100 years; dye: ~30–60 years	Same as home RA-4

My Assessment

For colour printing, the commercial RA-4 path (scan + lab printing) is probably the most sustainable option, combining the efficiency of industrial-scale chemistry use with systematic silver recovery. It's what I use for most of my colour output.

Home RA-4 makes sense when the wet darkroom experience itself matters—when I want to work directly from negative to print without digitisation, or when I'm doing experimental work that benefits from hands-on chemistry control.

Inkjet eliminates silver entirely but introduces different waste streams. For purely environmental optimisation with no other constraints, it's probably comparable to commercial RA-4.

Practical Recommendations for RA-4

If you're doing RA-4 printing and want to minimise environmental impact:

1. Use rotary drum processing

The chemistry savings are substantial. Over a year of printing, drum processing might use 5 litres of developer where tray processing would use 50.

2. Recover silver from blix

This is more complicated than B&W fixer recovery because of the ferric EDTA component. Steel wool displacement still works but is less efficient—the iron already present in the blix competes with the reaction. Allow longer treatment times (2–3 weeks rather than 1 week) and test before disposal.

Alternative: collect blix and take it to hazardous waste collection, which is what I currently do.

3. Maintain proper temperature

Processing at correct temperature reduces failed prints (waste) and ensures chemistry works efficiently (extending capacity).

4. Batch your printing

RA-4 chemistry has limited tray/drum life once mixed—developer oxidises within hours. Plan printing sessions to use mixed chemistry efficiently rather than discarding partially-used solutions.

5. Consider your actual needs

Not every colour image needs a wet print. Save RA-4 for work where the process matters; use digital output for proofs, casual work, and images that don't require the specific qualities of wet colour printing.

The Bottom Line

RA-4 colour printing is environmentally worse than B&W printing:

• CD-3 is more toxic than hydroquinone
• EDTA persists in the environment
• All paper silver becomes waste (though colour paper has lower silver content than B&W to begin with)

For B&W images specifically, traditional silver gelatin printing on RC paper produces marginally less silver waste than RA-4, plus avoids the CD-3 and EDTA issues. The difference is smaller than I initially thought due to colour paper's lower silver coating, but it's still in favour of B&W.

For colour output, commercial RA-4 printing from scanned files is likely more sustainable than home wet printing, thanks to industrial efficiency and systematic silver recovery. Home RA-4 makes sense for the experience and the full-analogue workflow; scanning + inkjet eliminates silver entirely.

RA-4 printing at home is a choice to accept certain environmental costs for aesthetic and process reasons. That's a legitimate choice—most photography involves such trade-offs. The important thing is to make it knowingly, address the impacts you can address, and not pretend the costs don't exist.

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