Communication: Why are the carrier densities of YBa2Cu3O7-x smaller in thin films prepared by wet-chemical methods than in those prepared by other methods? In order to answer this practically relevant question, the chemical reactions taking place need to be known exactly. The thermal decomposition of an organometallic precursor of YBa2Cu3O7-x -an important step in the wet-chemical preparation-has been investigated by the simultaneous application of dynamic and static characterization methods and the results are reported here.