Contact Printing

Part of Photography

Contact printing places a negative directly against sensitized paper and exposes it to light, producing a positive print exactly the same size as the negative — the simplest and most reliable printing method.

Why This Matters

A photographic negative is not the end goal. It is a reversed, intermediate record — dark where the scene was bright, light where the scene was dark — that can only be properly read by making a positive print from it. Contact printing is how you do this with the absolute minimum of equipment.

No projector, no enlarger, no additional lens is needed. The negative simply lies face-to-face with the printing paper, and light passing through the negative exposes the paper beneath in the exact same pattern, producing a positive image. Every bright area of the scene (dark in the negative) blocks light and remains light in the print. Every dark area (light in the negative) passes light and becomes dark in the print.

For practical documentation — copying maps, records, medical images, engineering drawings — contact printing is the workhorse of the photographic program. It requires only sensitized paper, a frame to hold negative and paper in contact, and a light source. With a large-format negative (10 × 15 cm or larger), contact prints are sharp enough for detailed technical records without any enlargement at all.

The Contact Printing Frame

The single essential tool is a printing frame that holds the negative and paper in firm, even contact during exposure.

Construction:

1. Build a rectangular wooden frame slightly larger than your standard plate size — for 9 × 12 cm plates, make the frame 12 × 15 cm internal
2. The frame has a front face (glass) and a hinged back with pressure springs
3. Front face: a piece of flat, clear window glass, framed in wood and hinged at one edge
4. Back: a wooden board cut in two halves, held closed by two bent-wire or carved-wood springs that press the halves together against the glass

How the hinged back works: The back is split so you can open half of it while the other half holds negative and paper in position. This allows you to inspect the progress of a printing-out exposure (when image forms visibly during exposure) without shifting the registration between negative and paper. You peek at one half, then close it and peek at the other half.

Simple frame without springs: Even simpler: cut a piece of glass. In the darkroom, lay the sensitized paper face up on a flat board. Lay the negative face down on the paper. Cover with the glass. Set a heavy book on top. This works perfectly for single prints in a fixed location.

Alignment marks: Scratch or paint small corner marks on the frame to help position negatives reproducibly. Consistent positioning lets you print multiple copies of the same negative with the same framing.

Printing Paper Preparation

Contact printing paper is sensitized paper that darkens when exposed to light. Several types work:

Silver chloride printing-out paper (POP): The most common traditional type. Light itself forms the silver image during exposure — no development needed, just fixing. The print appears as you watch it in sunlight. Requires only silver nitrate and sodium chloride to make.

Silver bromide/gelatin develop-out paper: The same material as your glass plates, but coated on paper. Requires development after exposure, same as negatives. Faster and more sensitive; can be exposed to lamplight in seconds.

Cyanotype paper (blueprint): Uses iron compounds instead of silver. Green color during exposure turns blue after washing. Extremely simple and cheap — no silver needed. Excellent for copying documents and line drawings where color accuracy does not matter.

Making simple printing-out paper:

1. Dissolve 5 g sodium chloride in 100 mL water
2. Brush onto smooth, heavy paper; let dry
3. In total darkness, brush 10 g silver nitrate dissolved in 100 mL water onto the salted paper
4. Silver chloride forms in the paper fibers — white, light-sensitive coating
5. Dry in total darkness; store in light-tight box

The Contact Printing Process

Light sources:

• Bright sunlight: the most powerful and free. Expose outdoors on a sunny day.
• Overcast daylight: works but requires 3-5 times longer exposure
• Oil lamp or candle: very slow (minutes to hours) but usable for printing-out paper
• Magnesium ribbon burned: extremely bright flash for single-exposure printing

Step-by-step (daylight printing-out paper):

1. In the darkroom under safelight, load the frame:

   • Lay sensitized paper in the back of the frame, emulsion side up
   • Place the negative face down on the paper (emulsion to emulsion contact)
   • Close the frame and lock the back springs

2. Carry the loaded frame to the light source. Point the glass front directly at the sun (or bright sky).

3. Expose until the image has printed to the desired density. For printing-out paper in direct sun, this takes 2-15 minutes depending on negative density and paper sensitivity.

4. Monitor progress by opening the hinged back halfway: the print-out image is faintly visible even in normal light. When the shadows (which will be darkened by fixing) look somewhat over-dark, the exposure is sufficient.

5. Return to darkroom. Remove print from frame.

6. Fix in sodium thiosulfate solution (200 g/L) for 5-10 minutes. The image changes color from red-brown to more neutral, and the overall tone lightens slightly.

7. Wash for 20-30 minutes in running or frequently changed water.

8. Dry face-up on clean cloth or hang on a line.

Step-by-step (develop-out paper):

1. Load frame in darkroom as above.

2. Expose to bright artificial light or sunlight for 1-10 seconds (much faster than POP).

3. Return to darkroom. Develop in pyrogallol or gallic acid developer for 3-6 minutes.

4. Rinse, fix, wash exactly as with a negative.

Exposure Control for Contact Printing

The test strip method: Before printing a full sheet, cut a strip of printing paper about 2 cm wide. Place this strip diagonally across the negative in the printing frame. Cover all but 2 cm of the strip with a card. Expose for 30 seconds; move the card another 2 cm; expose another 30 seconds; repeat 4-5 times. The strip now has segments exposed for 30, 60, 90, 120, and 150 seconds. Develop and fix the strip. Select the segment with the best tone and use that exposure time for the full print.

Factors affecting exposure time:

Factor	Effect
Dense (dark) negative	Longer exposure needed
Thin (pale) negative	Shorter exposure needed
Bright sunlight	Shorter exposure (2-5 min)
Overcast daylight	Longer (10-30 min)
Artificial lamp	Much longer (hours)
High-sensitivity paper	Shorter
Slow (chloride) paper	Longer

Making Multiple Prints from One Negative

The value of the negative-positive process is multiplication. One well-made negative can produce dozens of identical prints.

Protecting the negative: Each use in a printing frame risks scratching the glass plate. Place a thin tissue or transparent paper between the negative and the printing paper — this slightly reduces sharpness but protects the negative surface.

Keeping records: Number each negative. Record exposure times that produced good results. When printing a known negative a second time, start with the recorded time and make only one test strip to confirm conditions have not changed.

Batch printing: On a bright sunny day, load multiple printing frames with different negatives and print them all at once. Process them as a batch in sequence. This is efficient use of the chemicals and the good light.

Archival Quality

Contact prints, if properly processed, last centuries. The requirements:

1. Fix for the full recommended time in fresh fixer
2. Wash thoroughly — at least 30 minutes in running water, or change wash water 6 times over 30 minutes
3. Tone in gold chloride solution (1 g/L) for 5-10 minutes before fixing: this converts the silver to gold-silver, dramatically increasing stability against atmospheric sulfur
4. Never store prints in contact with rubber, wool, or painted wood — these emit sulfur compounds that tarnish silver
5. Interleave with acid-free paper when storing in stacks