Creativity and Science

Creating our own photo-paper.

John Herschel has invented blueprints in 1842. The invention is rather smart. A possible version for the laboratory: The paper is coated with a mix of iron salt (ferric chloride) and oxalic acid. Under UV ferrous oxalate is formed. A mask is applied to protect regions from UV exposure.The reaction product reacts in a further step with potassium ferricyanide to form an insoluble blue compound, known as Prussian blue. A further de-staining step ensures that no further reaction occurs.