Pyrocat-HD
A pyrocatechol-based staining developer designed by Sandy King as a modern alternative to PMK Pyro.[1] Pyrocat-HD uses pyrocatechol instead of pyrogallol, making it less toxic while producing similar staining characteristics. The HD stands for "High Definition" — it produces exceptional sharpness with minimal grain. The stain is more neutral in color than PMK, making it suitable for both silver gelatin and alternative process printing. Mixed as a two-part concentrate.[2]
References
- WEB alternativephotography.com alternativephotography.com. https://www.alternativephotography.com/ ↩
- BOOK The Darkroom Cookbook 4th ed. Focal Press, 2016. ISBN 9781138959170. ↩
Mixing Instructions
Pyrocat-HD is mixed as two stock solutions.
Solution A:
- Add pyrocatechol to 750 ml distilled water at 20 °C; stir until dissolved.
- Add phenidone and stir (phenidone dissolves slowly — be patient).
- Top up to 1 liter.
Solution B: Dissolve potassium carbonate in 1 liter of water at 20 °C.
Working solution: Mix 1 ml A + 1 ml B + 100 ml water (1:1:100). Use immediately and discard.
Wear gloves when handling pyrocatechol. Stock solutions A and B keep 6-12 months in tightly capped dark bottles.
Ingredients for 1L of Concentrate
| # | Chemical | Role | Qty (1L) | Unit | Note |
|---|---|---|---|---|---|
| 1 | Pyrocatechol | Developing Agent | 60.0 | g | (Solution A) |
| 2 | Phenidone | Developing Agent | 4.0 | g | (Solution A) |
| 3 | Potassium Metabisulfite | Preservative | 20.0 | g | (Solution A) |
| 4 | Potassium Carbonate | Accelerator | 750.0 | g | (Solution B) |
Process Parameters
| Film Stock | ISO | Dilution | Temp | Time | Agitation | Mix (per 1L) | Source | Notes |
|---|---|---|---|---|---|---|---|---|
| Fomapan 100 | 100 | 1:1:100 | 20.0°C | 9:00 | Continuous first 60s, then 10s every 60s | 10ml A + 10ml B + 980ml water | Community data | |
| Ilford Delta 100 | 100 | 1:1:100 | 20.0°C | 11:30 | Continuous first 60s, then 10s every 60s | 10ml A + 10ml B + 980ml water | Community data | |
| Ilford FP4+ 125 | 100 | 1:1:100 | 20.0°C | 10:00 | Continuous first 60s, then 10s every 60s | 10ml A + 10ml B + 980ml water | Community data | |
| Ilford HP5+ 400 | 320 | 1:1:100 | 20.0°C | 11:00 | Continuous first 60s, then 10s every 60s | 10ml A + 10ml B + 980ml water | Community data | |
| Kodak Tri-X 400 | 320 | 1:1:100 | 20.0°C | 11:00 | Continuous first 60s, then 10s every 60s | 10ml A + 10ml B + 980ml water | Sandy King | Rate at EI 320. Excellent sharpness. |