Fracture energy is determined by the energy required for the growth of cracks originating at defects or unglued patches. The failure of the glueline between Scots pine wood specimens was tested under tension perpendicular to the glueline (forced apart at one end) by the method of Ebewele et al. (see <i>FPA 4</i>, 1274). Resorcinol formaldehyde gluelines failed intermittently in a series of breaks, whereas elastomeric gluelines (e.g., polysulphide hermetic seal ) failed continuously, forming strands. Addition of liquid polysulphide rubber to the resorcinol formaldehyde adhesive increased the energies of both initiation and stopping of cracks. -- AATA