The Formation of Ice Crystals
John Pritchard
Award: Top 100
Award: Honorable Mention for Uniqueness
School: trinity school
Teacher: mark schober
Category: Contrived
Photo #21287
The Formation of Ice Crystals
The image seen above is a cyanotype, a cameraless type of photography using a
chemical reaction for exposure. To do this, I mixed two solutions, ferric
ammonium citrate and potassium ferricyanide which were then painted onto heavy
watercolor paper. The solutions were then left to dry for 90-120 minutes. For this
one, I used H 2 O undergoing phase change from a liquid to a solid. As the water
froze, the variations in the water layers caused ice crystals to form, spreading
across the paper, bending and scattering the UV light. When exposed to UV, the
Fe 3+ ions in the ferric ammonium citrate are reduced into Fe 2+ . The resulting Fe 2+
then reacts with the potassium ferricyanide, leaving behind ferric ferricyanide,
known as Prussian Blue. Places blocked from UV light cause the chemicals to not
undergo the reaction, and the unreacted chemicals are washed away during rinsing.
I changed multiple variables to alter the formations, through pre-exposure freeze
time, exposure time, water layer thickness, each time only altering one variable to
keep the experiment controlled. What I found worked the best was 2 minutes pre-
exposure, 6 minutes exposure at -17C, with an initially thin water layer, which was
then supplemented with another spray before starting the exposure. The additional
water created two different layers; one midway through freezing, the other
completely liquid.
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