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Natural Snowflakes
  --Photo Gallery I
  --Photo Gallery II
  --Photo Gallery III
  --Guide to Snowflakes
  --Snowflake Books
  --Historic Snowflakes
  --Ice Crystal Halos
  --Snowflake Store
Designer Snowflakes
  --I: First Attempts
  --II: Better Snowflakes
  --III: Precision Snow
  --Snowflake Movies
  --Free-falling Snow
  --Designer's Page
Frost Crystals
  --Guide to Frost
  --Frost Photos
Snowflake Physics
  --Snowflake Primer
  --Snow Crystal FAQs
  --No Two Alike?
  --Crystal Faceting
  --Snowflake Branching
  --Electric Growth
  --Ice Properties
  --Myths and Nonsense
Snow Activities
  --Snowflake Watching
  --Photographing Snow
  --Make Your Own
  --Snowflake Fossils
  --Ice Spikes
  --Activities for Kids
Snowflake Touring
  --Snowflake Hot Spots
  --Northern Ontario
  --Hokkaido, Japan (2) (3)
  --Michigan U. P.
  --California Mountains
Copyright Issues
Designer Snowflakes - Part Three
   ... Precision Snow ...
   The pictures on this page were taken using the same vapor diffusion chamber as in Part Two, but with a host of improvements. 
Better Snowflakes through Chemistry
quartet4ax.jpg (2954 bytes)composite2x.jpg (2974 bytes)   The first improvement came from my realization that the best electric needles grow only when certain chemical vapors are added to the diffusion chamber.  Silicone caulk vapor seems to work best, although acetic acid does almost as well, and even gasoline vapors do pretty well.  This trick allowed us to produce high-quality electric needles much more reliably than before. 
    The picture at right shows two near-perfect needles while they were growing, and after some small stars were grown on their ends.  The second images shows a quartet of electric needles, each with a snow star growing on its end.
Snowflakes on Electric Needles
compo1x.jpg (8124 bytes)comp23ax.jpg (3720 bytes)   To take advantage of our new needle-growing technique, we installed a high-power microscope objective right inside the diffusion chamber, so that we could produce higher-quality pictures of growing snowflakes.
   The two images at right are of the same snow crystal at different times; the left is after 5 minutes of growth, and the right image is after 10 minutes of growth.  The diameter of the larger crystal is about 1.2 mm.  The electric needle is out of focus, behind the crystal on the right side of the image.

These were grown with a special manipulator to orient the needles vertically


simpplatex.jpg (2610 bytes)At left is 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. 
plate1x.jpg (11459 bytes)Another timeseries showing pictures of a growing plate.  The diameter of the final crystal is about 0.5 mm, and the growth time was about 5 minutes.  Between the third and forth images the temperature was changed, which produced thick edges on the plate.
star61x.jpg (8234 bytes)star60x.jpg (5749 bytes)The two images at right are again pictures of the same crystal at different times; the first after about 3 minutes of growth, the second after 6 minutes.  The diameter of the larger crystal is about 0.8 mm.




bigstarx.jpg (10368 bytes)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.
The World's Largest Snow Crystal?
  Below are several pictures of a very large snow crystal, taken at various times during its growth.   The crystal is clearly a stellar dendrite, which grew on a string in a diffusion chamber in our laboratory.  After about 1.5 hours the crystal had grown to approximately one inch in diameter, as seen in the final image.
large1x.jpg (2423 bytes)large2x.jpg (2790 bytes)large3x.jpg (3486 bytes)large4x.jpg (3567 bytes)
Other Snowflake Structures
stringx.jpg (3120 bytes)  The picture at right is a nice demonstration of just how strange the growth of ice crystals really is.   The image shows crystals growing on a string hanging in a diffusion chamber.  The important feature of a diffusion chamber is its temperature gradient -- hot at the top and cold at the bottom.   The crystals growing on the string therefore grow at different temperatures.   The top cluster of crystals is growing at -2C, and these crystals grow in the form of flat, plate-like dendrites.  The middle cluster grows at -5C, and these form needle-like crystals.  The bottom cluster grows at -15C, and these too are plate-like dendrites. The spacing between the top and bottom clusters is 27 mm. Between these dominant clusters the crystals grow in more blocky shapes, and the growth rates are much slower.  This one picture demonstrates the temperature-dependent crystal growth seen in the snow crystal morphology diagram (see the Snowflake Primer).

Close-ups of the three different clusters (top, middle, at lower) are shown in the three images below.  One can also see water droplets above the top cluster, which mark the 0C temperature point on the string.

topx.jpg (1245 bytes)middlex.jpg (1737 bytes)bottomx.jpg (2077 bytes)

dendrite15x.jpg (5256 bytes)Even more details of these dominant growth forms are shown in this and the following three images.  The first picture, at left, shows a crystal grown at a temperature of -15C and high supersaturation (approximately 50 percent).  This crystal is plate-like, with well-defined dendritic sidebranches growing at an angle of 60 degrees from the primary direction.  The tip of the dendrite advanced at a velocity of 2.7 microns/second, along the a-axis of the crystal.  (For this image, and each of the following three images, the enlarged version is at a scale of two microns/pixel.)

dendrite2x.jpg (3238 bytes)The next image shows another dendrite, grown in our diffusion chamber at -2C.   The form is quite similar to the -15C dendrite -- a plate-like crystal with dendritic sidebranching.  The tip velocity was 1.2 microns/second, again along the a-axis.
fishbonex.jpg (4024 bytes)fishbone2x.jpg (2462 bytes)The two images at left are examples of what we call "fishbones" -- needle-like (columnar) crystals that grow at -5C under conditions of high supersaturation.  The left image is the normal growth on a substrate, in this case a thin wire.  The tip of the crystal advanced to the left with a uniform velocity of 2.0 microns/second, but the growth was not along a well-defined crystal axis.  Fishbones exhibit a different kind of sidebranching, with the branches growing roughly along the c-axis, as shown in the figure.
   The image on the right shows the start of a set of six fishbones, grown on the end of an electric needle (see Electric Growth).  The needle grew nicely along the c-axis, thus unambiguously defining the crystal axes.

Return to was created by Kenneth G. Libbrecht, Caltech
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