"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.
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;
- roller or brush;
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.
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.