The IB values for the PF-bonded Douglas-fir test samples decreased considerably with increasing veneer thickness (Table 3). Use of isocyanate adhesive increased the IB strength properties of the 0.125- and 0.167-inch veneer thickness 2-ply test samples to that of the 0.100-inch veneer thickness 2-ply test samples bonded with PF mixed glue. The IB values for the PF-bonded birch test samples averaged 346 psi. This value is close to the maximum perpendicular strength typically available with PF mixed glue resulting in the IB wood failure value of 27 percent.