we propose to study the decomposition of Pb diacetate trihtdrate in 4 different H,D combinations: Pb(CH(D)3COO)2.3H(D)2O. The quasi 2D lattice of Pb di-acetate is separated with H2O sheets of which the Water H(D) atoms are disordered between -115 K and 400K (120oC).Above 120 oC a decomposition takes place in several steps, loosing water and further organic material and finally transforming into most likely a form of PbO.The decomposition and phase transitions in the materials with H20 as sheet water is different from the materials with D2O as water layer.We propose to study the decomposition behaviour of the 4 H,D variants with thermo-diffraction from -40 oc to 450 oC in order to characterize the 2-d lattice destruction and the formation and structure deformation of related Pb-acetate containing structures into Leadoxide. In this case the change in background will function also as a DTA probe providing extra information on the decomposition process. The decomposition behaviour of Pb di-acetate trihydrate may provide information about its functioning as a paint hardener in paintings produced for 1850.