Our paintings conservator has been cleaning this idyllic view of the Seine for the past few days.  The varnish being removed is a highly stable synthetic resin that was applied forty or fifty years ago.  It does not seem to be discolored, but it’s being removed because there is discolored material beneath it.  Unfortunately, it looks like the waxy adhesive that was used to line the painting to another piece of canvas, shortly before the varnish was applied, was able to penetrate to the surface the painting. 

That material was then sandwiched between the paint and the varnish.  As you can see in the jar of used swabs on the right, the material being removed is just a faint dirty yellow.  But it’s enough to dull the colors in the scene.  Note how much brighter the right third of the painting is after it has been cleaned.

It’s likely that Hassam did not intend the picture to be varnished, so once this varnish and traces of lining adhesive have been removed, the conservator and curator will decide if it can remain in an unvarnished state.