I have changed the recipe to make a nicer playdough. It's softer, keeps longer and is not so hard on hands.
1 cup flour
1/4 cup salt
2 teaspoons Cream of Tartar
1 cup water
4 table spoons of olive oil
1 teaspoon food colouring
Mix the water, olive oil and food colouring in a pot. Add the flour, salt and cream of tartar. Heat on medium heat, stirring continuously until it forms a ball. Be careful that it does not burn.
Let it cool off a bit and then kneed for some time to mix it well.
When it has cooled off it can be stored in zip-loc bags or air-tight contained.
I found that the added olive oil keeps the dough soft, pliable and keeps my hands soft.
I also found that the playdough did not dry out so fast neither formed a white salty crust.
When the dough becomes dry, add a little bit of olive oil and not water.
(I made this batch in the beginning of February and my children still play with it.)