Hi Susan,
As a quick fix so you won't lose any more of the fire place try Paraloid B72. First do some small tests with the Paraloid and its different solvents (acetone, xylene, etc… . You don’t want to dissolve the painting).
Carefully, glue the flakes back… tedious work but that is what Conservation is at times :)
This will give you time to look for a better long-term solution.
Be careful and good luck,
Roeland Stulemeijer
Conservator
National University of Singapore Museums
E-mail: [log in to unmask]
Tel: (+ 65) 874 8817
Fax: (+ 65) 778 3738
10 Kent Ridge Crescent
Singapore 119260