Play dough is a semisolid which contains salt and is naturally electrically conductive. However, replace the salt with sugar and the play dough becomes an insulator! Both can be made easily and cheaply using flour, vegetable oil, water and salt or sugar. Students can then roll the dough into ‘wires’ or build more elaborate shapes into which they can then connect components. Great fun!
The recipes in metric units are available here.
The Squishy Circuits Classroom Guide contains the recipes as well as basic instructions and sample worksheets. There are also lots of fun ideas for using squishy circuits in electronics education on the Tinkering Studio website.