bittiness

D[ryden]’s lit[erary] patriotism [is] genuine, but he made good use of it to cover up the “bittiness” of his own plays. He could always point to the “bittiness” of Shakespeare and does not realize that though Shakespeare wrote tragi-comedies and indulged in double plots, he nevertheless attained an unity of his own, an unity that is missed in e.g. The Spanish Fryar.

‘Bittiness’ occurs when dirt is incorporated into the surface from the atmosphere or dirty tools, or if the paint is not properly strained.