Darkroom Setup

Part of Photography

A darkroom is the light-controlled workspace where light-sensitive photographic materials are handled, developed, and fixed — proper setup determines the quality of every photograph you produce.

Why This Matters

Photography requires two completely different environments: the bright outside world for taking pictures, and the absolute darkness of the darkroom for handling sensitive materials. Most failures in photography are not failures of chemistry or optics — they are failures of the darkroom. A single pinhole of white light striking an unprocessed plate destroys it. A developer tray at the wrong position causes confusion in dim red light and ruins a batch.

A good darkroom does not require a purpose-built room. Any enclosed space that can be made light-tight serves: a root cellar, a tent, a windowless storage room, even a large wooden cabinet. What it requires is systematic thinking about three things: light control, chemical organization, and workflow. Get these right and every photographic session proceeds smoothly. Get them wrong and you will be troubleshooting ruined plates for weeks before understanding why.

This guide covers permanent darkroom installation (for a settlement with ongoing photographic needs) and field darkrooms (temporary setups for survey teams, medical photographers, or expedition work).

Site Selection

Ideal permanent darkroom characteristics:

• No windows (basement, interior room, root cellar)
• Running water access, or a large water container with a drain
• Enough floor space for three working trays in a row plus standing room — minimum 2 × 3 meters
• Cool temperature: 15-22°C is ideal for chemistry; warmer accelerates development unpredictably
• Not adjacent to kitchens, smoking areas, or volatile chemical storage — fumes contaminate plates

Usable spaces:

• A root cellar with a single entry door: excellent, naturally cool, often no windows
• An interior storage room: suitable, seal gaps around pipes and conduits
• A tent or purpose-built wooden shed with no gaps: viable for temporary use
• A large wooden cabinet or chest: sufficient for single-plate developing; too cramped for batch work

Unsuitable spaces:

• Rooms with many windows (too many gaps to seal reliably)
• Rooms above forges, kilns, or smoky fires (smoke and fine ash contaminate plates)
• Rooms near water (moisture causes gelatin to swell and emulsions to soften)

Sealing Against Light

Every gap in the darkroom must be sealed. The standard test is to stand in the sealed room for 10 minutes and then look for any visible light. If you can see any glow, the room is not dark enough.

Door sealing:

1. Along the bottom of the door, attach a strip of folded heavy cloth or leather nailed to the door face so it drags on the floor
2. Along the sides and top, attach strips of felt to the door frame that compress when the door closes
3. If the door fits loosely in its frame, hang a heavy curtain inside the door that overlaps the frame on all sides by 20 cm
4. A light-lock entry (a second curtain or turn at the entry so you never open directly into the darkroom from outside) is ideal — no light enters even if someone opens the outer door

Window sealing:

1. Fit a tight wooden shutter to fill each window opening completely
2. Seal the edges with folded cloth or clay/putty pressed into gaps
3. Hang a heavy cloth inside as a secondary barrier
4. Apply lamp black (soot) or dark paint to window glass — this blocks all remaining light through glass

Pipe and conduit entries: Pack gaps around pipes with clay, fiber, or wedge-cut wood pieces. Any 2 mm gap in a darkroom is an unacceptable light leak.

Testing: Seal the room, wait 10 minutes for your eyes to fully adapt to darkness, then examine every wall, ceiling, floor, and door edge. Mark any glow with chalk. Seal all marked locations. Repeat until no light is visible after 10-minute dark adaptation.

The Safelight

Not all wavelengths of light affect photographic emulsions equally. Silver bromide and silver chloride are most sensitive to blue and violet light, and nearly insensitive to deep red light. This allows you to work in dim red illumination without fogging your plates.

Traditional safelight: A candle or oil lamp flame behind two layers of deep red cloth or glass. This produces barely enough light to see by — enough to orient yourself, handle trays, and see image emergence during development without fogging.

Making red glass: Window glass can be colored red by applying a mixture of red iron oxide and linseed oil in multiple thin layers. Allow each layer to dry completely. Five to eight layers produces adequate density.

Making a safelight filter: Soak cheesecloth or muslin in a strong solution of red dye (from madder root — see dyeing articles) and allow to dry. Double or triple the layers until the light through the cloth appears very dark red.

Placement: Mount the safelight at least 1 meter from any work surface where plates will be placed. The illumination falls off with the square of distance — doubling the distance reduces illumination by 75%. A safelight that is safe at 1 meter may be too bright at 0.3 meters.

Fogging test: Place an unexposed coated plate face up at your working distance from the safelight. Cover half the plate with a card. Expose for 5 minutes. Develop the plate normally. If the exposed half shows any uniform darkening compared to the covered half, your safelight is too bright or too close. Move it further away or add another layer of filter material.

Tray Layout and Workflow

The darkroom tray sequence must be arranged so that you always work in the same order and never reach over the wrong tray in dim safelight.

Standard linear arrangement (left to right):

1. Developer tray (leftmost)
2. Stop bath tray (plain water or 1% acetic acid — center)
3. Fixer tray (right)
4. Wash tray or running water sink (far right)

Tray specifications:

• Material: Glass, glazed ceramic, or well-varnished hardwood. Never bare metal.
• Size: Slightly larger than the plates (for 9 × 12 cm plates, use 12 × 16 cm minimum)
• Depth: 3-5 cm — enough to fully submerge a plate with 1-2 cm of solution above it
• Quantity: At least 2 developer trays (allows one to soak while you prepare the next plate); 1 stop; 1 fixer; 1-2 wash

Separate tongs for each tray: Never use the same tongs in developer and fixer. Even a tiny transfer of fixer into developer destroys the developer. Keep clearly different tongs for each tray — different shapes, or tied with different colored string.

Work Surfaces and Storage

Dry side (above the trays): A shelf or counter at comfortable working height for loading cameras, cutting paper, and storing equipment. This area must stay completely dry — wet hands carrying developer contaminate equipment.

Wet side (the trays): Lower surface where all chemical work happens. Slope the surface very slightly toward a drain point or collection basin.

Hanging system: A line with wooden pegs for hanging plates and prints to dry after washing. At least 50 cm above the wet work area.

Chemical storage: Mounted on the wall above the wet work area — dark bottles in fixed positions. Silver nitrate always in the same position; fixer stock always in its place. Know every position by touch.

Ventilation

Darkrooms must be light-tight but not airtight. Photographic chemicals, particularly developers (gallic acid, pyrogallol) and fixer (sodium thiosulfate), release fumes that irritate the respiratory tract and can cause headaches over long sessions.

Ventilation solution: A labyrinth vent — a Z-shaped or S-shaped passage in the wall through which air can circulate but light cannot penetrate. Cut a 10 × 10 cm passage through the wall, lined with black-painted board, with two 90-degree bends. Fit a small fan (hand-powered is fine) to move air through.

Minimum: work sessions under 1 hour without a break. Leave the darkroom for 5-10 minutes every hour in a long session. Never eat or drink in the darkroom.

Field Darkroom Setup

For survey teams or traveling photographers, a portable darkroom must be set up and broken down quickly.

The changing bag: A large, double-layer black cloth bag sewn into a lightproof pouch with elastic-sealed arm holes. Plates can be loaded into cameras and developed tanks inside the bag without any darkroom at all. Limited to small quantities but extremely portable.

The tent darkroom:

1. Erect a small tent (wool or canvas — not reflective materials)
2. Overlap the tent entry 50 cm and secure with pegs so it cannot blow open
3. Line the interior with a second layer of dark cloth
4. Work inside between midnight and before dawn — natural darkness outside makes light control easier
5. Chemical trays fit on a folding board or flat stone surface

Timing: In the field, plan developing sessions for early morning or late evening when ambient light is lower and heat is manageable. Do not attempt to develop plates in bright midday sun even in a tent.