To make a wallpaper paste that works and is free of pesticides, use 1 cup of wheat, corn or rice flour, 3 teaspoons of alum, water and 10 drops of oil of cloves. The clove oil acts as a natural preservative. Combine the flour and alum in a double boiler, or in a small pan set inside a larger pan which contains enough water to boil without overflowing into the smaller pan. Add enough water to the mixture in the smaller pan to create a consistency of heavy cream and stir until well blended. Heat the mixture while stirring constantly until it has thickened into a gravy like mixture. Let it cool, then stir in the clove oil. Pour into a glass jar with a screw top and apply with a glue brush. This mixture will keep in the refrigerator for 2 weeks.