Darkroom Chemistry: Mixing, Timing, and Disposal
The three-bath sequence — developer, stop, fixer — is the foundation of all darkroom printing. This page covers each chemical and how to use it correctly.
Developer — Dektol for Paper
Mix 1:2 with water (1 part developer, 2 parts water) at 68 F.
Developer — Dektol for Paper
Dektol is the standard paper developer. Mix 1 part stock solution to 2 parts water at 68°F. Develop RC paper for 90 seconds with continuous tray rocking. Develop fiber base paper for 2 to 3 minutes. Dektol oxidizes in the tray over time — a tray mixed in the morning may need replacement by afternoon. Signs of exhaustion: prints develop slowly with muddy shadows.
Stop Bath — Halts Development Immediately
Indicator stop bath shows color change when exhausted.
Stop Bath — Halts Development Immediately
Dilute stop bath (acetic acid) per manufacturer instructions — typically 1:63 for liquid concentrate. Agitate continuously for 30 seconds. Indicator stop bath turns from yellow to purple when exhausted — replace when you see color change. Stop bath is mildly corrosive — avoid skin and eye contact.
Fixer — Clears Unexposed Silver
Rapid fixer works in 1 to 2 minutes; standard in 4 to 5 minutes.
Fixer — Clears Unexposed Silver
Rapid fixer (ammonium thiosulfate) clears RC paper in 1 to 2 minutes. Standard sodium thiosulfate fixer takes 4 to 5 minutes. Agitate for the first 30 seconds, then every 30 seconds. Over-fixing fiber paper degrades the image silver. Test fixer freshness with Kodak Fixer Check solution — discard when it exceeds clearing time.
Silver-Laden Chemistry Is Hazardous Waste Used fixer accumulates silver from prints and negatives. Pour used fixer into a sealed container and take it to a photo lab or hazardous waste collection site. Do not pour down the drain. Developer and stop bath can be disposed of via household chemical waste programs — check local regulations.