How does Bacchus and Ariadne elucidate its Restoration?
The canvas on which Bacchus and Ariadne is painted was rolled up twice in the first century of its existence, which had consequences for the painting. From the turn of the 19th century onwards it was frequently being restored to stop paint from flaking off, with the most controversial restoration being that carried out at the National Gallery between 1967 and 1968. This greatly brightened the surface of the painting, and came as something of a shock to many viewers, used to a heavy varnish finish.  When discoloured varnish lying directly on top of the paint surface was removed, some of the paint itself came off as well and repainting was necessary.This has caused some critics to note that the expanse of blue sky on the left-hand side, one of the worst-affected areas of the painting, appears flat and pallid. It has also been argued that the removal of the varnish has left the painting tonally out of balance, since Titian is likely to have added some subtle glazes to the paint surface in order to tone down some of the more jarring colors. The National Gallery maintains that this was an unavoidable loss, because the accrued layers of later varnish had turned the painting brown and sludgy and had to be removed.  More recent examination has confirmed that the paint remains largely original.
Titian varnish Bacchus National Gallery Ariadne