The formula for Silly Putty is a proprietary one owned by the Crayola company since it acquired the manufacturing rights in 1977. The original Silly Putty was made from combining boric acid and silicone oil. It's possible to make a homemade version using Elmer's glue and liquid starch.
It is reported that the original, coral-colored Silly Putty consisted of 65 percent dimethyl siloxane, 17 percent silica, 9 percent Thixatrol ST, 4 percent polydimethysiloxande, 1 percent decamethyl cyclopentasiloxane, 1 percent glycerine and 1 percent titanium dioxide.
It's possible to create a homemade version by mixing equal parts of Elmer's Glue-All multipurpose glue with Sta-Flo liquid starch. The addition of food coloring dyes the putty.
To make the homemade putty, place the glue in a small, non-porous mixing bowl. Add a couple of drops of the food coloring, if desired, and mix thoroughly to evenly distribute the food coloring. Add the liquid starch and mix thoroughly again. Allow the mixture to stand for 5 minutes.
Remove the homemade putty from the bowl and place it on a piece of paper towel or wax paper. Knead the putty for five to 10 minutes, until the mixture feels smooth and elastic. This recipe produces putty that bounces if rolled into a ball shape and copies newsprint if stretched out and pressed to the paper.