Kazuhiko Hiramatsu
Asahikawa Nishi Senior High School,Asahikawa,Japan

1. Introduction :" Have you seen the growth of snow crystals ?"
Previously we could not create snow crystals indoors unless we used a big refrigerator or other equipment. I invented the new method which allows anyone to create and observe snow crystals at hardly any cost. It was in 1936 that Dr.Ukichiro Nakaya and his subordinates succeeded in producing the first artificial snow crystals in a cold laboratory. Since then, several types of equipment had been made, but these require such large costs that cannot be incurred easily by anyone.The apparatus that I invented in 1996 is so small and has simple structure, that the instructor can easily introduce in the classroom. This method becomes gradually popular in Japan due to media coverage by newspapers and television.
Especially young people who live in the areas that have no snowfall in winter, are interested in this experiment. This is also useful for the demonstration in the museum events.

2. Object of the experiment
2.1 Observation of growing process of snow crystals

2.2 Learning the necessary conditions for growth of snow crystals through making and controlling the apparatus.

3. Making an apparatus
3.1 Materials
a 500ml polyethylene terephthalate resin (PET) bottle, a styrofoam cooler box with a lid,1-1.5 kg dry ice, a thin fishing filament, a rubber plug and an plastic eraser

3.2 Tools
a hammer, a cutter and a stapler

3.3 Methods and observation
a) bore a hole at the center of the lid as a PET bottle just fits.
b) fix a small piece of an eraser to a fishing filament by a stapler
c) set an plastic eraser to the bottom as an anchor
d) blow into the PET bottle several times
e) plug up the bottle
f) in about 5 minutes small needles of snow crystals grow
g) in about 40 minutes large dendritic snow crystals grow

4. Merits of this apparatus
4.1 Easy to make the apparatus using everyday materials such as a PET bottle , a styrofoam cooler box and so on.

4.2 No frost on the surface of the upper part of the bottle.Therefore easy to observe the snow crystals growing inside..

4.3 It totally takes only 1 to 2 hours to make an apparatus and observe snow crystals growth.

4.4 In the PET bottle a miniature stratospheric condition exists,so the temperature is consistently maintained at -15 at the level of the lid. It is just optimum condition for the growth of dendritic snow crystals .

5. Effects
5.1 Inspiring scientific curiosity
5.2 Understanding the meteorological conditions in natural clouds where snow crystals nucleate, grow and precipitate

6. Two associated experiments
The same apparatus offers the opportunity to watch ice crystals (babies of snow crystals ; Japanese nickname:"diamond dust". Besides transparent PET bottle enables us to make clouds inside.

6.1 Observation of ice crystals
a) blow into the bottle several times (supply water vapor)
b) pop a babble packing to occur adiabatic expansion in the bottle.
c) torch reflects faces of ice crystals to be observed

6.2 Observation of cloud
a) cut the upper part of the PET bottle and pour water 1 cm deep
b) put ice and salt into an aluminium can
c) strike a match in the bottle to make nuclei
d) set the can on the PET bottle
e) milky cloud go down in the bottle

7. Conclusion
Textbooks teach students how snow crystals are formed but students hardly have a chance to actually see the process. I regard creating snow crystals in the classroom as a part of demonstrating natural beauty in cold regions to students. This innovative experiment are likely to encourage students to become more interested in nature around them.

8. References
Hiramatsu,K.(1996): Making snow crystals in the cozy living room(Article of Hokkaido Shinbun:Daily Newspaper, Japanese)
Hiramatsu,K.(1998): Making snow crystals in the PET bottle, Kodomo - No - Kagaku vol.61,Seibundo-shinkosya,Tokyo,(Japanese)