“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