Okay, yes. After further research I figured out that,
When clay dries (without being fired yet), water evaporates from it. This is reversible. It can be broken up again and recombined with water.
However, when clay is fired, there is a temperature at which 'chemical-water' leaves the clay. Again, water is leaving the clay, but this time there is a chemical reaction going on. This is (moreorless) not reversible. It canNOT be broken up and recombined with water.
sources:
http://www.bigceramicstore.com/information/tip31.htm
www.ceramicartdaily.net/PMI/KilnFiringChart.pdf