Utilizing Nature Print paper, which is sensitive to UV light, is a great way to parallel the process that engineers use in the cleanroom in order to make small devices such as microchips with UV light!
The paper has been treated with two water-soluble chemicals that appear blue in color together.
When exposed to UV light, these molecules will undergo a chemical reaction and form a new colorless molecule. Areas not exposed to UV light do not undergo the chemical reaction, and therefore remain blue.
Students are able to create unique and interesting designs by creating their own pattern with dark ink on a transparent film or by scratching the film off of a transparency coated in black wax, the way that engineers use what's called a 'photomask' to protect certain parts of their chemically-treated wafer from UV light. You would be amazed at the creativity that comes out when students learn that art and science can be combined!
Once students designs have been transferred to the UV paper using UV light (either from the sun or from UV flashlights), students will need to undergo a final step to make their design permanent. This is called the 'developing' step. If the developing step is skipped, the design could be ruined as soon as it is exposed to UV from other sources such as the sun's rays!
In order to develop the print, it is fully submersed in water. This causes two things to happen: (1) the blue water-soluble compounds that the paper was initially treated in get dissolved in the water and washed away and (2) the chemical reaction that occurred where the paper was exposed to UV light oxidizes in the water and forms the pigment 'Prussian blue', turning it from white back to blue. The end result is that the colors switch - what was blue becomes white, and vice versa!
