Caffenol (C-M)
A developer made from coffee, baking soda, and vitamin C—no store-bought chemicals.
About the Developer
Caffenol works because of the polyphenols in instant coffee, which develop the film much like a conventional developer—baking soda makes the solution alkaline, and vitamin C enhances and accelerates the reaction. The solution must be used immediately after mixing: it oxidizes quickly and loses its effectiveness.
Character
A soft developer with low contrast and noticeable grain; it is sensitive to the brand of coffee, the proportions, and the freshness of the reagents, so the results are less consistent from batch to batch than those of commercial formulations.
Best films
It works best with ISO 100–400 films of standard and low contrast: Fomapan/Neopan 100, Kentmere 100/400, Ilford Pan F+/FP4+, Delta 400. For ISO ratings above 100, a pinch of restrainer salt is required to suppress fogging.
How to Mix and Use
- 1Pour it directly into the tank and develop at 20°C.
- 2Pacing: continuous for the first 30 seconds, then 3 inversions per minute.
- 3Drain the water, rinse the film with water several times, secure it in place, and rinse it thoroughly.
Development time
| Film | ISO | Time @ 20°C |
|---|---|---|
| Fomapan / Neopan 100 | ISO 100 | 15 min |
| Ilford Delta 400 (with salt) | ISO 400 | 15–20 min |
For film with an ISO rating higher than 100, add a pinch of salt—it reduces the haze (fog) caused by coffee at high ISO settings.
Pros
- The ingredients are available at any grocery store—no photochemical supplies are needed
- Inexpensive and environmentally friendly: the reagents are low-toxicity and easy to dispose of
- A good educational example for understanding the chemistry behind the phenomenon
Cons
- The working solution has a short shelf life—use within one hour
- The result depends significantly on the brand and variety of coffee, which reduces reproducibility
- It doesn't handle high ISO settings as well and produces a more pronounced fog without a restrainer
Recipe for 1 liter
Chemical structures: PubChem (public domain)
Mixing it at home
A developer made from instant coffee, washing soda and vitamin C — no store-bought photochemistry. Dissolve the soda in a separate container: it warms up noticeably when it meets the vitamin C.
- 1Dissolve the coffee in some water.
- 2Separately, dissolve the baking soda in the other portion of water.
- 3Mix the coffee and baking soda solutions, then add the vitamin C last.
Key points
- The working solution lasts about an hour: coffee developers oxidise quickly, so mix it right before developing.
- Use plain instant coffee with no additives — it is the coffee acids that act as the developing agent; different brands give different contrast and grain.
- The C-M recipe is aimed at films around ISO 100. There are versions for stand development (less soda, lower fog) and for a speed boost (a little potassium bromide added to the solution to hold back fog).