What happens to Fiba-Zorb in
extreme drying-out conditions?

Fiba-Zorb is not only added to enable initial fast and even wetting but to ensure that if the potting soil ever becomes really dried out it can then be re-wet and that the water is absorbed evenly and thoroughly without any dry areas.
 

The effect of Fiba-Zorb in really dried-out peat was investigated by Fachhochschule Weihenstephan in Germany.
 

In cycle 1 you can see the water uptake with a standard dose of Fiba-Zorb.  In the figure you can also see the difference in water after drying out once and twice in the air (AD) and in the oven (OD) plus drying out once and twice in storage and oven drying (S+OD).
 

The conclusion is that Fiba-Zorb is very beneficial even after extreme drying-out.