1. Snow Crystal on Electric Needles. Here is a picture of a snow crystals grown on the ends of an electric needle. It was grown with a special manipulator to orient the needles vertically, and imaged using a high-power microscope objective placed inside the diffusion chamber.

2. A simple sectored plate grown at the end of an electric needle; the plate diameter is about 0.4 mm. To growth such a plate the supersaturation level needs to be quite low.

3. This image is a picture of a crystal after 6 minutes. The diameter of is about 0.8 mm.

4. A large snow star, for which the electric needle is right behind the crystal and therefore not visible. The crystal diameter is about 1.5 mm.

5. This page shows a snow crystal grown in the Snow Crystal Lab at Caltech during 1999. The image was taken as part of our ongoing investigation into the morphology and dynamics of ice crystal formationand were grown in free-fall, which has some advantages for making quantitative measurements.

6. This crystal and the last image crystals were grown, with other crystals under quite similar conditions, although some grew for a longer period of time before falling onto the observation window.

7. This crystal was grown along with the last two images. The longest growth time was about two minutes. Even the small variations in temperature and supersaturation within the growth chamber resulted in the great variety of forms.

8. Growth at -2 C. At -2 degrees Celsius snow crystal growth becomes plate-like, although the growth rates are not as high as at -15 C. Thus the plates are smaller, and they show some qualitative differences. Larger crystals, which grew at the highest supersaturation levels, show distinctive rounded extensions. These reflect the roughening transition that occurs near the melting point — the ice surface becomes microscopically rough, so the crystal boundaries are no longer faceted.

9. This image shows a small plate-like crystal, which was grown at a temperature of about -13 C, slightly warmer than the dendrite peak (see the snow crystal primer for details). The crystal was created by first growing a thin “electric” ice needle. Once the ice needle had reached the desired length, the high voltage was turned off, and the crystal was moved to a region in the growth chamber that had the desired temperature. At this point the plate-like crystal began growing at the needle’s tip.

10. Here’s a good example of a designer snowflake. It was grown at about -14 C, quite near the dendrite peak, and at a fairly low supersaturation. Under these conditions the needle tip immediately sprouted six dendritic arms. At various times during growth the crystal was moved to -7 C for just a few seconds, and then moved back to -14 C; this operation caused a pair of sidebranches to sprout from each of the six main arms. All the sidebranches on the crystal were induced using this procedure; none grew otherwise. Tip-to-tip diameter is 1.8 mm.
Check out a movie showing the crystal growing (3 Mbyte)
http://www.its.caltech.edu/~atomic/snowcrystals/gallery98/movie3.gif

11. A fairly large crystal, approximately 2 mm in diameter. The ambient temperature varied slightly during the crystal growth, changing from about -14 C to -13 C. Note that there is a great deal of structure in the sectored plates at the ends of the arms, reflecting the somewhat higher supersaturation (compared to the pictures above) during growth.

12. A fairly well-formed dendrites, which form at a temperature of around -15 C. Note the appearance of sectored plates, which results from either lower supersaturation or slightly higher temperatures.