Re: Why did my balloon create less static the more I rubbed it on a wool fabric

Hi Kathleen!

I have two ideas on what may be happening.   

First, if paper confetti clings to the balloon, then some charge from the
balloon may slowly move to the confetti.   The more humid the environment,
the faster the charges can move.   If a lot of charge moves in this way,
then the paper bits will be repelled, and they'll start leaping off the
balloon.   But if only a little charge moves onto the paper bits, it won't
create repulsion, but will only weaken the attraction force.  Then if you
knock the confetti off the balloon, the balloon will only weakly attract
this alike-charged confetti.   The cure:  use a new batch of confetti each
time you do the test.   (If your problem was caused by charged confetti,
then the problem will vanish if you use new and uncharged confetti.)


If using different confetti each time does not solve the problem, then
here's a second possibility.  If your wool blanket was ever washed while
using fabric softener, or if your clothes dryer has been exposed to an
"anti-static dryer sheet" such as Bounce(tm), then the blanket has a slight
coating of oil.

If the blanket fibers have any oil at all, then this oil will be deposited
upon the balloon surface as you rub.   Soon the wool will not touch rubber,
but instead you'll be touching oil against oil.  (Even a microscopic
coating of oil will cause problems.)   The balloon might charge strongly at
first, but with more rubbing the charge will decrease.

A possible cure:  wash the blanket using plenty of detergent, then let it
air-dry in a warm environment.  When fully dry, use a blow-dryer to get it
warm and "static-y".   Don't put it in a clothes
dryer which may still contain oil from an anti-static sheet used earlier.


Also note:  a charged balloon attracts uncharged confetti.  Why?  The
confetti is neutral, so why is it attracted?  Charged objects always
attract neutral objects.  The neutral confetti contains equal amounts of
positive and negative charges.  The negative balloon repels the confetti's
negative charges, and atttracts the confetti's positive charges.  You might
think that this push and pull would be exactly equal, so the confetti would
not move in either direction.  But the charges inside the confetti can move
very slightly.  The negatives inside the confetti move slightly away from
the balloon, while the positives move towards the balloon.  Now the
positives inside the confetti are slightly closer to the balloon, so their
attraction becomes slightly stronger than the repulsion.

This is called "Attraction by Electrostatic Induction".   The opposite
charges inside the confetti were "induced" to become slightly separated.

See "Charged attracts uncharged" in:  http://amasci.com/emotor/sticky.html