The play dough in the picture is over a month old and shows no signs of age, no drying and is as pliable as the day I made it. My daughter likes to add colors to her play dough- this batch started out a cream color and very quickly became a dark green/black!
2 t cream of tartar
1 c water
1 T cooking oil
Stir constantly until mixture pulls away from pan and can be formed into a ball.
Turn out onto counter top or cutting board and let it cool a bit, then kneed it until it reaches desired consistency- this won't take more than a minute or two.
Make sure to store your play dough in an air-tight bag or container to prolong its life.