Weight gain as a measure of whether a board will exhibit delamination after
soldering is not a test with any history that I know of at this point.
 1)  How can you be certain that the board does not have too much moisture in
it before you clean it to result in delam?
2)  How much is too much?
3)  How does different builds effect the amount of moisture absorbed?  Does
the moisture remain between the outermost layers or is it absorbed into the
center of the board?

My other questions is - are you an assembler doing the cleaning prior to
assembly?

Susan Mansilla
Technical Director
Robisan Lab