The words "silly putty" can instantly bring back childhood memories of spending hours with friends stretching this pliable toy to incredible lengths. The stuff is comprised of silicone oil and borax and will stretch, bounce, flow slowly like a liquid or shatter if hit with a hammer. Silly putty will harden if left in an area of the home that is not well-heated. Heating silly putty increases its stretchiness, returning it to a malleable state. As long as the silly putty has not expired -- it lasts up to two years -- it can be softened.
Knead the putty with your hands. The more you work it, the softer it will become.
Roll the silly putty with a rolling pin or similar object if your hands get tired or you find the putty has not softened enough. Place the putty on a sturdy, clean surface and put as much of your weight as you can on the rolling pin to flatten and soften the putty.
Heat the silly putty if it has not softened enough. Place the putty in a beaker and put the beaker on a tin plate. Place the tin plate on a heat plate and adjust the temperature to 77 F, or room temperature. Allow it to heat for 1 to 3 minutes. The silly putty will return to its stretchy state, according to a silly putty lab experiment conducted by the students of Fisher Middle School in Los Gatos, California.