Pans are lined with parchment paper to ease the process of removing a baked product from the pan. For creamed or foamed batters that must be spread rather than poured, it is important to apply a thin film of butter or other fat to the pan before placing the parchment in the base of the pan. The fat will keep the paper stationary while the batter is spread. This is particularly important when using large pans. The sides of the pan should also be greased and lightly floured, or greased with pan grease, which already contains a measure of flour. Pans used for sponge cakes should be lined with parchment but the sides of the pans should remain untreated so that the sponge cake may pull itself up the pan.