The tensile shear strength of the wood substrates that were treated at elevated temperature with conditioning method D is also presented in Fig. 5. None of the wood substrates bonded with gum dispersions are significantly affected by the heat treatment. They all show a very good heat resistance. The wood substrates bonded with the xanthan gum dispersion do not fulfill the WATT 91 limit of 7 MPa but an improvement in the tensile shear strength is actually seen after the heat treatment. The wood substrates bonded with the other gum dispersions fulfill the limit of 7 MPa. The cyclic structure, the possibility of hydrogen bonding and the high molar mass of the