How to capture a falling snowflake

Who hasn't marveled at a lacy snowflake coming to rest on a jacket sleeve? Do you wonder how it could survive the fall to earth in one piece?

A snowflake begins high up in the clouds, not as a snowflake but as a small particle of dust, salt, or ash. When a cloud cools below 32 degrees F, some specks of water vapor freeze onto the particle. As it moves through the cloud, the particle absorbs additional water vapor, building up microscopic layers of ice. When water molecules freeze, they bond together in a way that forms a six-sided ice crystal.

Eventually, the ice crystal becomes too heavy to stay aloft in the cloud, and it begins the descent to earth, usually with many others like itself. This is the precipitation we call snow. A snowflake can be a single ice crystal, but it's usually a cluster of crystals, often two hundred or more, all symmetrically connected. The common feature of all ice crystals, and thus all snowflakes, is the hexagonal structure of branches, short stub-like arms, or sides.

Snow crystals are categorized by their general shape. There is the familiar intricate star-shaped snowflake, called a stellar dendrite. Spatial dendrites also have branches, but they are more untidy and dissimilar. Plates have just the suggestion of arms growing at the six corners of the hexagon. Other common types are: needles, columns (which look like short, unsharpened pencils), and capped columns (which look like columns with graduation caps attached to the ends).

Eighty snow crystal varieties have been formally identified, catalogued, and labelled by scientists who study the world of winter. Two books with exquisite photographs are The Snowflake: Winter's Secret Beauty (Libbrecht and Rasmussen) and Snow Crystals (Bentley and Humphreys).

Different cloud temperatures and humidity levels determine the snow crystal's initial size and shape. Thin, plate-like crystals grow when temperatures are close to the freezing point. At cooler temperatures, needles, columns, and dendrites appear. Additionally, higher humidity produces more intricate designs, while simpler forms of plates and columns occur in drier air.

Finding a perfectly intact snowflake is a treat. Snow crystals are tossed about by the wind and encounter different temperatures and levels of humidity. Pieces may break off or melt, or crystals that collide might stick together. So, can two snowflakes be exactly alike? Only if they attract water vapor in a cloud in the exactly same way, fall through exactly the same temperature and moisture conditions and swirl in identical aerial dances.

It is easy to collect snowflakes for your own enjoyment and study. Keep a sheet of stiff black paper in the freezer, ready to grab when flakes start falling. Stand out of the wind and let snowflakes land on the paper. Then retreat to a protected area that is cold, such as a garage or covered deck. Use a magnifying glass to study the individual flakes.

You can also preserve snowflakes on a glass microscope slide. Keep the slide in the freezer and a can of clear acrylic spray in the refrigerator. When you are ready to go outside, put on gloves (you do not want the slide to warm up in your hands), spray the acrylic onto the slide, and dash outside. You can hold the slide in your outstretched hand, or place it on a level spot. Let a few flakes fall onto it, then place it in a protected spot outside for a few hours. The snowflakes will freeze into the plastic spray, which also freezes, creating a permanent impression of your snowflakes. Under the microscope you will be able to see tiny parts of snowflakes that you missed with your own eye.

Barbara Mackay is a teacher and naturalist who lives in northern Vermont. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation: wellborn@nhcf.org.

Through the lens

By Erin Day

I recently got a new camera, a Canon T3i, and was able to get clear shots with a small macro lens attachment to get close-ups of snowflakes.

I went outside in the afternoon while it was still snowing, cleared off the railing on my deck, and waited until I saw a cool snowflake fall. Then I took a bunch of pictures until I got a few that came out really clear. When the railing got too snowy I'd just brush it off with my sleeve and wait for more to appear.

Every snowflake looks so different you could stand outside for hours and never get the same picture. I did use the macro setting on the camera but didn't use any filters or editors. I only cropped a bit of the picture so the snowflake looked bigger and was more of the centerpiece.