Développement N&B · 2026-09-11

Developing with Coffee, Paracetamol, or Vitamin C: A Practical Guide to DIY Developers for Black-and-White Film

Caffenol isn't some lockdown kitchen experiment that went viral. It's a documented developer with roots in the 1990s, tested on thousands of rolls by a serious community of film photographers. The reason to dig into it here isn't novelty, it's that understanding what's actually happening chemically in these recipes gives you a clearer picture of how any developer works. That's worth something.

What's happening in the tank: the chemistry, plainly stated

Any silver-based developer, commercial or homemade, depends on three things: a developing agent (which reduces exposed silver salts to metallic silver), an accelerator (which creates the alkaline pH the reaction needs), and usually a preservative (which slows premature oxidation).

In Caffenol, the primary developing agent is caffeic acid, a phenolic compound naturally present in instant coffee. Phenols can reduce silver ions to metallic silver, which is exactly what you need. The problem is that coffee is acidic, and developing agents require an alkaline environment to do their job. That's where sodium carbonate (also known as washing soda or soda ash) comes in: it raises the pH to a workable range, around 11-12. Vitamin C, in the form of ascorbic acid or ascorbate salt, acts as a secondary developing agent and contributes to superadditivity: combined with the phenols in coffee, it substantially speeds up the reaction and cuts development times.

Parodinal follows the same basic logic but with different chemistry. Its developing agent is para-aminophenol, which is structurally close to the active ingredient in Agfa's original Rodinal, hence the name. That's also why Parodinal behaves similarly to Rodinal when diluted: pronounced grain, high acutance, long development times at high dilutions, and excellent shelf life in concentrated form.

The three functional roles in a Caffenol developer — schematic overview, not a reaction diagram.

The Caffenol-C-M recipe: where to start

There are several Caffenol variants, but Caffenol-C-M (Medium Speed) is the community standard for a first attempt. For 1 litre of working solution:

54 g of anhydrous sodium carbonate (or around 150 g of hydrated crystals)
16 g of ascorbic acid (pure vitamin C powder, not flavored chewable tablets)
40 g of instant coffee

The order of mixing matters. Dissolve the sodium carbonate in roughly 700 ml of water at room temperature (20°C / 68°F), then add the vitamin C, then the coffee. Top up to 1 litre. The sodium ascorbate solution that forms during mixing oxidizes fairly quickly, so mix the Caffenol fresh and use it the same day. No point making a stock bottle in advance.

Typical development times at 20°C (68°F):

Film stock	Time at 20°C	Agitation protocol
Ilford HP5+ (ISO 400)	13–15 minutes	Continuous first 30 s, then 3 inv/min
Fomapan 400	~15 minutes	Same protocol
Kentmere 400	Close to HP5+	Same protocol

These figures are based on the standard Caffenol-C-M protocol: 15 minutes at 20°C, agitation for the first 30 seconds, then 3 inversions each minute. Treat them as a range, not a fixed law. The exact concentration of caffeic acid varies with the brand of instant coffee you use, and that's a source of variability you can't fully eliminate.

The Caffenol-C-H (High Speed) variant adds 1 g/litre of potassium bromide to the C-M recipe, with no other changes. Development time stays at 15 minutes, or 30 minutes for semi-stand with agitation only during the first 30 seconds.

Semi-stand development: useful, not magic

A lot of photographers who use Caffenol end up gravitating toward semi-stand, typically 60 minutes with minimal agitation. The appeal is that a slower reaction gives you more margin to compensate for variability in the solution. On Fomapan 100 or Kentmere 100, results are often soft with well-detailed shadows.

One thing that becomes clear quickly with Caffenol is that results vary considerably between film stocks, and that's even more true with semi-stand. A film that responds well can give excellent results, and another can disappoint in identical conditions.

Parodinal: the recipe and what to watch out for

Parodinal is based on paracetamol (acetaminophen), sodium sulfite, and sodium hydroxide. The most widely used recipe for 100 ml of concentrated stock:

10 tablets of 500 mg paracetamol (5 g total), crushed to a fine powder
50 g of anhydrous sodium sulfite
20 g of sodium hydroxide (lye / caustic soda)
Water to make up to 100 ml

The sodium hydroxide hydrolyzes the paracetamol to release para-aminophenol. The reaction is exothermic, so the solution heats up noticeably as the lye dissolves. The sodium sulfite serves both as a preservative and as a developing agent modifier. The result is a concentrated brown solution that keeps for months or even years in a tightly sealed bottle.

In use, Parodinal is very flexible. It keeps well in concentrated form and works across a wide range of dilutions: 1:25, 1:50, 1:100, and up to 1:200. Development times are close to Rodinal for the same film stocks, which makes finding starting points straightforward. The Rodinal data on the Massive Dev Chart is a reasonable baseline, with a few minutes of adjustment worked out through testing.

Practical results on three common film stocks

With Ilford HP5+, Caffenol produces a contrasty result with visible but consistent grain, more pronounced than you'd get with D-76 or Ilfosol 3. Midtones hold up well as long as you don't underexpose. HP5+'s wide exposure latitude makes it forgiving in Caffenol, which is part of why it shows up so often in these tests. In Parodinal 1+50, acutance is very high, edges are crisp, and grain stays within reasonable limits for a 400-speed film.

Fomapan 400 is trickier. Its real-world speed tends to land around ISO 320 in practice, and Caffenol doesn't change that. Go more than half a stop under and the shadows are gone. Exposed correctly, though, it gives images with real character. Dirk Essl's work on caffenol.org is the best starting point for Fomapan development times, far more reliable than something pulled off a forum thread.

Kentmere 400 is probably the most cooperative of the three for alternative development. Its emulsion is predictable, and Caffenol-C-M results are consistent from roll to roll, provided you weigh your ingredients accurately. It's often the one recommended for a first attempt, and for good reason.

Qualitative grain comparison — relative values only, based on the observations in the text. Not a measurement chart.

The real limitation: repeatability

Here's the honest thing to say about DIY developers. With a commercial developer like D-76 or HC-110, you're working with an industrially controlled formulation. With Caffenol, you have one variable that's genuinely hard to pin down: the caffeic acid content of your instant coffee. It shifts with the brand, the batch, freshness, and roasting method. Most recipes call for instant coffee because it's a more consistent source of caffeic acid than brewed coffee, but "more consistent" isn't the same as "consistent." Once you find a brand that works, stay with it.

Even with all of that, you'll see contrast variations between rolls that you wouldn't get with a commercial developer. That's not necessarily a dealbreaker if you're comfortable with some unpredictability in your results. But if you need tight consistency to feed a well-calibrated printing workflow, Caffenol probably isn't your main tool.

Parodinal is somewhat better on this front, because the solution is stable once mixed and the raw material variation is much smaller than what you're dealing with in coffee. Its chemical similarity to Rodinal also means there's a broader base of published development data to draw from.

Going further

For Caffenol, caffenol.org is the essential reference: tested development times for dozens of film stocks, all in one place. Cross-referencing with filmdev.org is also worth doing, to see what the wider community has published for specific film/developer combinations.

For weighing ingredients, a 0.1 g precision scale is not optional. Entry-level lab or jewelry scales run between $20 and $40 and do the job fine. That's genuinely the only piece of equipment you need to get started with Caffenol.

For Parodinal, the original thread on Photrio.com (Film Developing section) is a better starting point than any summary you'll find elsewhere. It documents recipe variations and long-term results from people who've been using it for years. The base formula has been stable for a long time, but the discussions around pH and concentration adjustments are genuinely useful for understanding what's actually going on chemically.

Developing with Coffee, Paracetamol, or Vitamin C: A Practical Guide to DIY Developers for Black-and-White Film

What's happening in the tank: the chemistry, plainly stated

The Caffenol-C-M recipe: where to start

Semi-stand development: useful, not magic

Parodinal: the recipe and what to watch out for

Practical results on three common film stocks

The real limitation: repeatability

Going further

Sources