You'll have to take numerous photos of the damage and recount how the damage occurred in as much detail as you can and in writing. A database like
Artwork Archive helps you keep all documents related to it including photos of damaged artwork, in order.
A brief overview of the history of an artwork.
You will need to send photographs of the damage to any restorer you choose to hire (many require such documents prior to supplying an estimate) and
to your insurance company if you intend to file a claim with your insurance company if you plan to file a.
Andrei states that most people need estimates prior to sending in artwork. I require photos of both the front and back of the artwork as well the dimensions.
For me, the billing process is based on the work. The cost will be determined by the work hours and difficulty.