Work done in the author's laboratory has indicated that polyflavonoid tannins can self-condense to a hardened network without the addition of any hardeners. This allows their use as interior grade adhesives for wood panels. For fast-reacting tannins, such as procyanidins, the catalytic effect exercised solely by the lignocellulosic substrate is enough to give strength performance satisfying relevant standards. For slower-reacting tannins such as prorobinetinidins and profisdetinidins, small amounts of finely divided SiO2 dissolved in a tannin solution in water at pH of 11-12 is sufficient to catalyse such a self-condensation effect. As there are no added aldehydes, there is little or no detectable formaldehyde.