“How to print a retro photograph at home” experiment
You’ll need only salts and gelatin!
Did you know that you can print a photograph without a printer? For example, the only devices you’ll need in this experiment are a stencil, glass, paper and… the sun!
Safety precautions
Wear protective gloves and glasses
Warning! Only under adults supervision.
Reagents and equipment:
- gelatin (3 g);
- sodium chloride (5 g);
- 1% silver nitrate solution;
- 10% sodium thiosulfate solution;
- water (400 ml);
- cotton swab;
- glass container;
- thick paper;
- beakers (2);
- stencil (or negative);
- 2 pieces of glass with the size of the photograph.
Step-by-step instructions
Prepare two beakers with warm water: 100 ml in the first, and 300 ml in the second. Dissolve gelatin in the first glass, and sodium chloride in the second. Mix the solutions together in the glass container and lower the paper into it, to soak it on one side. Dry it for 20 minutes. With the cotton swab, apply the silver nitrate solution to the treated surface. Leave it in a dark place until it dries completely. Place a photograph stencil (or negative) on the paper and put it between the two pieces of glass. Put it under bright light, for example sunlight, for 3-5 minutes. The photograph appears! Now rinse it with water to remove the residue of the reagents, and with sodium thiosulfate, to preserve the picture
Processes description
In the reaction of silver nitrate and sodium chloride solutions, insoluble silver chloride forms. Light causes the silver chloride to decompose with the formation of silver and chlorine, and the photograph appears. The gelatin acts as a holding agent, so the photograph does not become blurred and the silver does not enter the layer of paper too deeply, and the sodium thiosulfate acts to preserve the picture.
AgNO₃ + NaCl = AgCl + NaNO₃
2AgCl + light = 2Ag + Cl₂
