Uploaded January 2021 | Updated September 2026, 3 weeks ago
Chemical printing, or your favorite image on a postcard in 10 minutes
Equipment: sodium carbonate, citric acid, ammonium iron(III) sulfate, potassium hexacyanoferrate(III), beaker, cotton roll, watercolor paper, negative image, hair dryer.
Dissolve sodium carbonate, citric acid, ammonium iron(III) sulfate, and potassium hexacyanoferrate(III) in water to create a light-sensitive mixture. Use a cotton roll to apply this solution to a piece of watercolor paper, then cover the paper with a negative image and set the paper and negative under a lamp. After 10 minutes, remove the negative image and rinse the paper with water, then dry it with a hair dryer – you’ve made a cute winter postcard!
Under the influence of bright light, the iron(III) ions in the photosensitive mixture begin to actively enter an excited state. At the same time, they oxidize citric acid ions, resulting in the formation of a complex mixture of organic substances and iron(II) ions, with which potassium hexacyanoferrate(III) forms an insoluble blue compound:
Fe²⁺ + K₃[Fe(CN)₆] → KFe[Fe(CN)₆]↓ + K⁺
This compound is firmly fixed in the pores of the paper, so when rinsed with water, the blue pattern remains!
A similar experiment is included in the “Cyanotype” set from the MEL Chemistry subscription.
Warning: only under adult supervision.
Chemical printing, or your favorite image on a postcard in 10 minutes
Equipment: sodium carbonate, citric acid, ammonium iron(III) sulfate, potassium hexacyanoferrate(III), beaker, cotton roll, watercolor paper, negative image, hair dryer.
Dissolve sodium carbonate, citric acid, ammonium iron(III) sulfate, and potassium hexacyanoferrate(III) in water to create a light-sensitive mixture. Use a cotton roll to apply this solution to a piece of watercolor paper, then cover the paper with a negative image and set the paper and negative under a lamp. After 10 minutes, remove the negative image and rinse the paper with water, then dry it with a hair dryer – you’ve made a cute winter postcard!
Under the influence of bright light, the iron(III) ions in the photosensitive mixture begin to actively enter an excited state. At the same time, they oxidize citric acid ions, resulting in the formation of a complex mixture of organic substances and iron(II) ions, with which potassium hexacyanoferrate(III) forms an insoluble blue compound:
Fe²⁺ + K₃[Fe(CN)₆] → KFe[Fe(CN)₆]↓ + K⁺
This compound is firmly fixed in the pores of the paper, so when rinsed with water, the blue pattern remains!
A similar experiment is included in the “Cyanotype” set from the MEL Chemistry subscription.
Warning: only under adult supervision.
