"Chemistry of printing: Cyanotyping" experiment

How to make a print on a T-shirt

Did you know that you can make a print on a T-shirt us­ing chem­istry? Here’s an en­ter­tain­ing ex­per­i­ment which al­lows you to print a pic­ture us­ing light and a pho­to­chem­i­cal mix­ture.

Safe­ty pre­cau­tions

Wear gloves when con­duct­ing this ex­per­i­ment

Reagents and equip­ment:

  • cit­ric acid (10 g);
  • iron (III)-am­mo­ni­um sul­fate (22 g);
  • am­mo­nia so­lu­tion 3% (40 ml);
  • so­lu­tion of potas­si­um fer­ri­cyanide (potas­si­um hex­a­cyano­fer­rate (III) (60 ml);
  • glass bowl;
  • 4 beakers;
  • T-shirt;
  • sten­cil;
  • roller or brush;
  • lamp.

Step-by-step in­struc­tions

To make the print on the T-shirt, first pre­pare the sten­cil. Make a neg­a­tive of the pic­ture that will be print­ed on the T-shirt. Print this neg­a­tive on trans­par­ent film. Or you can use the in­struc­tions from MEL Sci­ence: how to make a sten­cil on elec­tron­ic me­dia.

Now pre­pare the light-sen­si­tive mix­ture: mix the cit­ric acid and the iron(III)-am­mo­ni­um sul­fate, add the 3% am­mo­nia so­lu­tion and mix. Dim the light and add the so­lu­tion of potas­si­um fer­ri­cyanide. The re­sult­ing mix­ture must be stored in a dark place to avoid ex­po­sure to light.

Then take the T-shirt and ap­ply the mix­ture in an even lay­er. Cov­er the soaked area with a sten­cil and shine the lamp on it. Af­ter an hour, re­move the sten­cil and rinse the pic­ture in cold wa­ter to re­move the re­mains of the mix­ture. On the T-shirt we ob­serve a blue print of the pic­ture from the sten­cil.

Pro­cess­es de­scrip­tion

Un­der the im­pact of light, cit­ric acid re­duces iron(III) in fer­ric am­mo­ni­um sul­fate to iron(II). Iron(II) re­acts with potas­si­um fer­ri­cyanide, form­ing a bluish pig­ment – Berlin blue. Im­por­tant: only wish the T-shirt with neu­tral de­ter­gents.