Ukichiro Nakaya - Snow Crystals

Snow Crystals

From 1933, Nakaya observed natural snow and created 3,000 photographic plates of snow crystals, classifying them into seven major and numerous minor types. In the course of these observations, taking photographs of natural snow and sorting them by appearance according to weather conditions, Nakaya felt the need to make artificial snow from ice crystals grown in the laboratory. He generated water vapor in a dual-layer hollow glass tube, which was then cooled. Contrary to his initial expectations, creating snow crystals was not an easy task – instead of forming into snowflakes, the ice crystals grew like caterpillars on the cotton string he used for nucleation.

The Low Temperature Science Laboratory opened in 1935, and experiments continued with various materials for the ice nucleus. These experiments revealed that woolen string is better than cotton string; however, the snow crystals were still not forming as intended. One day Nakaya found a snow crystal on the tip of a hair of a rabbit-fur coat in the lab. This was the breakthrough that led to the production of the first artificial snow crystal. On March 12, 1936, three years after the first attempt, he produced a snow crystal on the tip of a single hair of rabbit fur in his laboratory apparatus. In December 1937, he took photographs of many types of artificial snow crystals in his lab. These photographs were influenced by Wilson Bentley's 1931 book Snow Crystals, which he admired greatly.

Nakaya continued his research into snow crystals and elucidated how their various patterns are produced in nature. He published his Nakaya Diagram, which describes the relationships among vapor, temperature, supersaturation, and excess vapor density in clouds.