Wood samples after bathing (23 degrees C, 24 h) in acidic (pH 4) or alk. buffers and drying (40 degrees C, 24 h) were light-irradiated (Xenone lamp, 550 W/m(2), waves length 290-800 nm or 320-800 nm) for 1-100 h and evaluated for color changes of wood and chem. changes of its surface. The results were compared with those for the untreated wood samples. Colorimetric methods and IR spectroscopy were used to assess discoloration of wood and chem. changes of its surface, resp. Alk. bath and light irradn. at waves length 290-800 nm resulted in the most significant darkening of the wood surface and the largest degrdn. of lignin.