Retention of red color in Taiwania (Taiwania cryptomeriodes Hay.) heartwood

Taiwania (Taiwania cryptomeriones Hay.) is one of economically important tree species indigenous to Taiwan. The heartwood of Taiwania is yellowish red with distinguished purplish pink streaks. Unfortunately, the "red" color is susceptible to change to dull black after exposure the heartwood to natural environment. This discoloration is a serious defect that decreases the value of Taiwania products. In order to preserve the red color of Taiwania heartwood, aliphatic polyurethane (PU) clear coatings containing Tinuvin photostabilizer coupled with pretreatment using photostabilizers, polyethylene glycol (PEG), semicarbazide (SCB) and acetic acid, were used. The experimental results demonstrated that discoloration on the surface of Taiwania heartwood could be prevented by pretreating it with photostabilizers (Tinuvin-1130 and Tinuvin-292) or PEG or SCB, followed by finishing it with a PU coating containing Tinuvin-1130 photostabilizer. The discoloration could be reduced to 30% of that of the untreated specimen by treating it with photostabilizers pretreatment or PEG pretreatment followed by finishing it with a PU coating containing Tinuvin-1130 photostabilizer. Furthermore, the discoloration was proven to reduce to 10% of that of the untreated specimen by treating it with SCB pretreatment followed by finishing it with a PU coating containing Tinuvin-1130 photostabilizer.