STEAMING OF POPLAR, BLACK LOCUST AND BEECH TIMBERS SIMULTANEOUSLY TO INVESTIGATE COLOUR MODIFICATION EFFECT OF EXTRACTIVE TRANSPORT

This paper deals with a colour modification method of poplar (Populus x euramericana cv.Pannonia) without any chemicals or stains.Steaming was found to be a proper modification method to change its natural greyish-white colour to a more attractive brown tint.Black locust and beech timber (as initiators) were steamed together with poplar timber to intensify its colour change.Treatment temperatures were 90 °C; 100 °C; 110 °C and 120 °C.Maximum duration of steaming was 20 days (9 days at 120 °C).The colour change of sapwood and heartwood was monitored separately using the CIE Lab colour system.A wide range of hues was created using this treatment method ranging from the initial colour to brown depending on the steaming time and temperature.The presence of black locust or beech wood facilitated the colour change of poplar only above 100°C.In terms of the colour alteration of different wood parts, these initiator species were more effective in the heartwood part than in sapwood.Chromophore molecules generating the yellowness increase did not prove to be stable at 120 °C.Higher treatment temperature tends to partly degrade these molecules resulting in reduced yellowness values.