Carolyn,
 
There is no easy, single, solution to your problem.  Solvents should not
affect ceramic artifacts, or other non-porous, non-coated artifacts.
 
Furniture presents a couple of problems, as you already know.  What may
work in your favor is that the furniture may not have been particularly
clean when the white out was applied and you may be able to simply pop it
off with a blunt tool (i.e., a gently applied table knife) and finish up
with furniture polish.  However, the white out may have been on long
enough, or in an exposed enough area, that the area protected from the
sun/light by the white out may now look cleaner/brighter.
 
If it seem that solvents may have to be resorted to, contact a local
conservator for advice.  It may be that the solution is not difficult.
 
Good luck.
 
Jack C. Thompson
Thompson Conservation Lab.
Portland, OR
 
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