The curves of increase of modulus as a function of temperature obtained by thermomechanical analysis (TMA) of joints bonded with different polyflavonoid tannins-hardener systems show a succession of different plateaus. Equally, the increase of modulus first-derivate curves show a succession of several peaks. Both the position and extent of the plateaus of the modulus curve as well as the peaks of its first derivate curve show considerable apparent variability in relative intensity and sometime in relative position on the thermogram. This variability appears to be due to the superimposition of the series of polycondensation reactions of the different phenolic nuclei, which constitute the flavonoid repeating unit of each tannin with each different hardener on the pattern of plateaus peaks induced by the noncrosslinked entanglement networks formed by the Linear increase of the polymer in the early stages of the polycondensation. This succession of stages in the thermograms is described not only for a procyanidin type and for a profisetinidin prorobinetinidin type tannin, but also on the basis of the TMA results of the polycondensation of simple phenolic model compounds of the tannin nuclei as well as of linear, noncrosslinkable model polymers for the entanglement networks case. The effect of different polycondensation hardeners on the extent of tannin autocondensation indicates that the more marked the polycondensation, the earlier entanglement networks appear, and the lower the temperature at which they appear. Autocondensation is always shown to participate to the formation of the final, hardened tannin network, more or much less markedly, according to the hardener used. The proportion of the network due to polycondensation appears to be related to the extent of water resistance of the final network, while the contribution of tannin autocondensation appears to be only limited to the dry strength of the network. It is also shown that the traditionally accepted "comfortable" correspondence of gel point and start of vitrification with features of the TMA-obtained modulus increase curves loses its significance in complex systems such as flavonoid tannins, in which phenolic sites of greatly different reactivities coexist on the same molecule. A progression of formation and successive tightenings of a network by different mechanisms induced by sites of different reactivity describes better the reality of the situation.