|
Issue Date: December 16, 2007
More than just a pretty bow
The physics of curly ribbon
It may be the thought that counts, but a beautifully wrapped holiday gift still goes a long way -- and there's science in that art. The curliest, prettiest bow depends on changing the molecular structure in the ribbon with the perfect flick of the wrist.
Use a slow hand when making curly ribbons.
|
Just ask Buddhapriya Chakrabarti, the Martha Stewart of physics. In a quest to perfect the technique and discover what puts the curl in a ribbon, he conducted a scientific test while at Harvard.
You've seen it done: Pass a ribbon between your thumb and a scissor blade, and it springs into a tight curl. Chakrabarti discovered that the best technique requires a very sharp blade, tension in the ribbon (pull it as tight as possible for the best results) and, counter to conventional wisdom, a slow hand.
You may scrape either side of the ribbon, which causes the top surface -- the one against your thumb -- to stretch more than the bottom. "One side of the ribbon hasn't deformed much," Chakrabarti says. "But the other side elongates much more."
As a result, the shorter side contracts and causes the ribbon to curl.
Most gift-wrappers are taught to scrape quickly, but using a slower movement gives the ribbon time to relax into its new molecular arrangement. The technique doesn't work on fancy woven ribbon, like satin, in which the sides can move independently. You must use the thin, inexpensive ribbon called "curling ribbon."
-- Karen C. Fox
|
|
