old dirt and varnish being removed from a 17th century marine painting
An example of how cleaning can recover the painter's intention:
A Barbizon School painting circa 1870
In the past a thick and irregular layer of an undefined composition was applied to the reverse.
The old smear is mechanically removed, showing the original canvas
The sky proves to have been altered in the past in a random manner according to the skill or taste of the restorer; the threatening skies are an imaginative addition, very helpful to hide a problem. This was not uncommon in the past, restorers giving the painting a an interpretation entirely of their own.
Part of the overpainted clouds is removed…
and now the threatening clouds have completely disappeared and after retouching and varnish it proves to be a find day after all!
before and after: a difference of day and night!