Fresco is a painting medium that has no binder as the pigment is mixed into the plaster prior to applying to the surface - a wall. Because of the quick drying time only a portion of the wall can be completed each day. There are two basic types of fresco. True or buon fresco is what was just described. Fresco a secco is done after the plaster has dried. In this type a different binder (tempera, oil, etcetera) is used. In some cases and for some colors a secco is used on a buon fresco after it has dried.