Ingredients for Silly Putty (Dow Corning 3179 Dilatant Compound)
(Percentages by weight)
65% Dimethyl Siloxane, hydroxy-terminated polymers with boric acid
17% Silica, quartz crystalline
9% Thixotrol ST
4% Polydimethylsiloxane
1% Decamethyl cyclopentasiloxane
1% Glycerine
1% Titanium Dioxide
I am not a chemist but in layman's terms, this is silicone oil and boric acid
(Found at http://www.thebuzz.net/ingredie.htm)