Answer:
union:Hall, which has gained considerable acceptance, unione (Italian: [uˈnjoːne]) is one of four modes of painting colours available to Italian High Renaissance painters, along with sfumato, chiaroscuro and cangiante. Unione was developed by Raphael, who exemplified it in the Stanza della Segnatura.
sfumato:It is a technique of color employed without hard lines.
Unione is characterized by its sfumato quality. It seeks vibrant color what Sfumato attempts more soberly. Union eliminates strong tonal contrasts and employs color harmony while still maintaining vibrant color.
hope that helps..