Playing with clay dough is a staple of childhood pastimes. Use this simple recipe which dries and hardens without baking to fill up a long rainy day.
Put cornstarch and baking soda into a large saucepan. Stir to mix it up.
Stir constantly while adding a little water at a time. It will be very smooth and thin to start.
When it thickens to the point where you can't stir it, it's done. Put the dough on a baking tray. Cover it with a paper towel so that it doesn't dry out. You can also use a dish towel that's been wet and wrung out.
Put the whole pan full of dough on a good sized baking tray. After it cools down, knead the clay until it feels nice and smooth to the touch.
Roll the dough out and you can cut it with an Exacto knife or cookie cutters. You can also shape things with your hands or squeeze it through a cookie cutter bag. This clay makes lots of neat things - including great Christmas ornaments.
After you design your objects, let them air dry. The drying time will vary depending on the thickness of the item. Most things will be dry in about one day. You can put it into the oven at 176 degrees C if you want to hasten the process with thick pieces, but it will air dry fully if you are patient.
Clay will keep in the refrigerator for up to 2 weeks. Seal it in a zipper type plastic bag, pressing most of the air out of it before you seal it.
Clay can be tinted with food colouring or with natural food colouring dyes (see articles on making dyes from vegetables here on eHow).
The clay will harden too much to use if you leave it in the fridge or on the counter top too long before you use it.