Borax (called 20 Mule Team Borax Laundry Booster - the product called Boraxo will NOT work)
Optional: blue food coloring
Make a giant snowflake frame from 3 white pipe cleaners and string. Twist the 3 pipe cleaners together in the center to make a 6-sided, spiky figure.
Make sure this figure fits inside the wide-mouthed jar.
Tie the string around the pipe cleaners to look like a snowflake shape. Trim the excess string.
Tie a few inches of string to one of the pipe cleaners. Tie the other end of the string to a pencil, so that the snowflake will hang from the pencil and dangle inside the jar.
Take the snowflake out of the jar.
Pour boiling water into the jar. Add the 20 Mule Team Borax Laundry Booster to the hot water in the jar.
Keep adding the Borax until you have a supersaturated solution (you will see undissolved Borax at the bottom of the jar). You'll have to add about 3 tablespoonfuls of the 20 Mule Team Borax Laundry Booster to each cup of hot water in the jar.
Optional: Add a few drops of blue food coloring for a bluish snowflake.
Hang the snowflake in the jar and wait at least overnight.
In the morning, your snowflake will be covered with beautiful crystals.
As the supersaturated solution cools, the borax comes out of solution (less of the borax can dissolve in cool water) and forms crystals on the pipe cleaners and string.