Restoring Old Masters

Analyze with UV, Infra Red, X-Ray

Remove varnish, using an enormous range of solvents

Relax cracks, in-paint

Restoration is political as well as technical;  people like what they're used to seeing, not perhaps what the artist intended.  
Ref row over Sistine Chapel, and that brewing over plans for the Mona Lisa.

The head of the department of painting conservation and restoration

- a diminutive Scottish woman who is one of the brightest and most articulate people I've ever heard speak

Almost as fascinating - the esoteric processes of shipping and receiving the masterpieces which museums around the world lend to one another