The Comparison of the Effect of UV Irradiation and the Combined Effect of UV Irradiation and Water Leaching on the Color of Grey Poplar
A series of grey poplar (Populus x canescens) samples was irradiated by strong ultraviolet (UV) light emitter mercury lamp, while another series of specimens were treated with the combination of UV irradiation and water leaching. The total duration of UV irradiation for both series of specimens was 20 days. The colour parameters (CIE L*, a*, b*) were measured and evaluated after both UV irradiation and water leaching. Due to the 20 days of UV irradiation, the initial redness value of sapwood increased 2.69 times, while leaching reduced this factor to 1.77. In case of heartwood, the initial redness value increased 1.34-fold due to the 20-day UV exposure, while the leaching reduced this factor to 1.14. These multiplier values are 2.07 and 1.44 for the yellowness of sapwood, as well as 1.57 and 1.29 for the yellowness of heartwood. The leaching partly removed the yellow and red chromophore molecules generated by the UV irradiation. The samples were slightly lighter after water leaching