How to Get Snow Crystals

Snowflakes are marvelous creations.

Snow crystals, or snowflakes, form when water vapor condenses out of supersaturated air. Supersaturated air has a relative humidity greater than 100 percent and forms when warm, moist air mixes with cool air. Supersaturated air condenses into ice crystals when the air temperature drops below 32 degrees Fahrenheit. Given the right temperature and humidity conditions, a single ice crystal will continue growing. Try growing your own snow crystals at home. It's fun and easy to do.

Things You'll Need

• Used 20-ounce plastic soda bottle
• Sharp knife
• Sewing needle
• Small kitchen sponge, ½ inch thick
• 4 straight pins
• Nylon fishing line, 1-pound test
• Scotch tape
• Paper clip
• 32-ounce Styrofoam cups, 3
• Dry ice
• Gloves
• 2 plastic grocery bags
• Hammer
• Spoon
• Cardboard
• Paper towels

Instructions

1. Rinse the soda bottle out and recap it. This will be the snow crystal growth chamber.

2. Cut the bottle in two with a sharp knife. Make the cut ½ inch from the bottom of the bottle.

3. Poke a hole in the center of the bottle bottom with a knife or sewing needle. Poke four holes around the sides of the bottle bottom.

4. Place a small sponge inside the bottle bottom. Secure the sponge in place with straight pins. Insert the pins through the side holes.

5. Thread the fishing line through the eye of the sewing needle. Insert the needle through the hole in the bottle bottom. Make sure it goes through the sponge. Remove the needle. Tape one end of the fishing line to the bottle bottom. Tie a knot in the other end to hold the paper clip.

6. Reassemble the bottle. Turn it upside down.

7. Stack the Styrofoam cups, one inside the other. Place the inverted bottle inside the top cup so the bottom of the label is level with the top of the cup. Leave a 1-inch gap between the top of the cup and the sides of the bottle.

8. Remove the bottle bottom. Moisten the sponge with tap water. The sponge should be wet, but not dripping. Reassemble the bottle.

9. Place the dry ice inside the plastic grocery bags and crush it with a hammer. Do this on a solid surface, such as asphalt or concrete. Place the crushed dry ice in its Styrofoam cooler.

10. Fill the top cup with dry ice. Use a spoon. Cover the cup with a piece of cardboard or strips of paper towels. Wrap paper towels around the top to keep it from "sweating."

11. Add dry ice as needed.

12. Observe. After five to 10 minutes, you will see small ice crystals forming on the string. After 1 hour, you should see a number of crystals. The crystals will look like fishbones and dendrites. Fishbone crystals have a feather-like appearance, while dendrite crystals have a fern-like appearance.

Tips & Warnings

• If you can't find 32-ounce Styrofoam cups, make a bucket from pieces of Styrofoam packing material. Cut the pieces to size and make an open-top box. Make sure the box is deep enough to hold both the dry ice and the bottle. Glue the pieces together with silicone glue, which is available at hardware stores.

• Look in the Yellow Pages under Dry Ice to find a retailer. You will need 10 pounds of dry ice for each experiment.

• One charge of dry ice will last six hours.

• Dry ice is very cold. Wear gloves when handling it.

• Use plenty of dry ice. If you don't use enough, the experiment won't work.

References

• Kenneth G. Libbrecht: Grow Your Own Snowflakes

Resources

• Kenneth G. Libbrecht: Snowflakes and Snow Crystals