What is the chemistry behind "silly spray" to make it shoot out of the
can and instantly solidify?

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Request for Question Clarification by alienintelligence-ga on 07 Sep 2002 00:12 PDT

Remember when it was flammable?

Posted on: 07/28/2000
"Hot Off the Wire" By Mark Bromann 
"Here are some notable news and product announcements for the fire
protection industry from off the news wire."
[ http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,7669,00.html
]
"Consumer Product Recall Alert"
"The U.S. Consumer Products Safety Commission, in conjunction with
three California manufacturers, is recalling 912,000 cans of silly
string. The propellant from cans of "Crazy String" and "Crazy Ribbon"
is extremely flammable, representing a serious risk of burn injuries
when sprayed close to open flames, such as birthday candles. Since
this product is used mainly by children, this should be one recall of
particular interest to everyone."

So I guess you want a reference to the 'new' chemical
composition? Although I don't believe the swap from
one propellant to another matters in the solidification.

-AI

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Clarification of Question by bobafett8t88-ga on 08 Sep 2002 13:26 PDT

I'm more curious about the concept than the specifics of each and
every ingredient of silly string.  If the same chemical processes were
carried out when it was flamable as they do today, then I wouldn't be
concerned with such minor modifications to the recipe.  I'd really
like to know what main active ingredient(s) is responsible for the
instant change between liquid and solid once it touches air (oxygen?),
and what causes this change to occur.
I hope that clears up the confusion.  Thanks

If "Silly Spray" is the same thing as "silly string" it might be
difficult to find out.

"Precious little is known about the origins or ingredients of Silly
String. First introduced to the gag-gift market in 1969 by Julius
Samann, Ltd., the only thing that is known about Silly String is that
it is non-toxic, non-flammable, and completely free of
chlorofluorocarbons. Beyond that, no one, save the manufacturer, knows
the exact ingredients of this top-secret tool of pranksters. No
ingredients are listed on the can and the manufacturer refuses to say
what they are, claiming that is information is “proprietary."
http://www.yesterdayland.com/popopedia/shows/toys/ty1069.php

Unofficially, it is Polyisobutylmethacrylate, plasticized with DBP.

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&threadm=375F900E.CA278E3%40pacifier.com&rnum=16&prev=/groups%3Fq%3Dsilly%2Bstring%26hl%3Den%26lr%3D%26ie%3DUTF-8%26start%3D10%26sa%3DN