Children's Play Dough

2 cups flour
1 cup salt
1/2 cup cornstarch
1 Tbsp. powdered alum
2 cups water
1 Tbsp. oil
In 2 quart glass dish blend four, salt, cornstarch, and alum.  Whip in water and oil until mixed.  Microwave High 4 - 5 minutes, stirring every minute until mixture is thick and lumpy.  Cool on flat plate.  Knead on floured surface until smooth.  Store in covered jar in refrigerator.  Color when kneading if desired.