[MurrayHurps]

I'm thinking very sensitive scales to measure both the bread and the plate before and after the test period, which should answer that question definitively.

The question now though is, how much would that condensation weigh? And hence how accurate do the scales need to be?

[vl]

1 cubic centimeter of water weighs 1 gram. This looks like 1/10 of cubic centimeter at most. Milligram scale should work - $20 at Amazon, but you'll have to use rather small plate (the more you weigh, the less precise the measurement of difference between two objects).