1/2 cup salt
1 cup flour
2 tbs cream of tartar
1 cup water
1 tablespoon oil
Few drops of food colouring.
Mix the dry ingredients in a saucepan then add the wet ingredients. Stir over a low heat for a few minutes until the mixture starts to congeal. (I know when this happens because my hand and arm start to ache!) Once it's a solid lump, allow to cool before turning out onto a floured board and knead lightly to ensure all heat from the middle is released before giving to children.
This recipe is based on the one in the ABA's NMAA Cooks - Recipes for Busy Mothers, which is a fantastic cookbook full of old-fashioned cheap and easy to make recipes. You can buy it from Mother's Direct or get more info from the Facebook page.
You can also find the recipe in double the quantities on the back of packets of McKenzie's Cream of Tartar. I sometimes also add glitter and / or a few drops of lavender essential oil. For older kids, if you don't mind messy hands, add the food colouring drops into the middle after it's been cooked and cooled and then let the kids knead the dough which changes colour as if by magic.
Home-made playdough will keep for several weeks in an airtight container.