I own a child care center and this is the play dough recipe we use it is very easy and last a while. We double it.
1 cup of flour
1 cup of water
2 tsp. cream of tartar
1/2 cup salt
1 tablespoon oil
Place in a microwave safe bowl and mix together.
Place in microwave on high for 3 minutes. Stop after each minute to stir.
Let cool a bit it will be hot.
You may add food coloring or liquid water colors or an extract for color/scent after it has been made. We have even added cinnamon for scent.