The restoration of some wood materials exposed to outdoor conditions by bleaching process

There brings out physical, chemical, biological and microscopical changes in unprotected wooden material which is exposed to weathering conditions and so its structure and color are spoiled. The objectives of this study are to restore the faded color of the wooden material which is exposed to weathering conditions with bleaching process and to try to gain the natural color, gloss and hardness values of the material. For this reason, Scotch Pine (Pinus sylvestris Lipsky), Eastern Beech (Fagus orientalis Lipsky), Sessile Oak (Quercus petraea Lieble) and Chestnut (Castanea sativa Mill) woods have been exposed to weathering conditions for 12 months by essentially taking ASTM D-1641 into consideration. Later on, bleaching process has been applied to the surface of the samples with 18% solution group S1 (NaOH + H2O2), S2 (NaOH + Ca(OH)2), S3 (KMnO4 + NaHSO3 + H2O2) S4 (NaSiO3 + H2O2) and commercial solution group S5 (Cuprinol Decking Restorer- (H2C2O4 + C2H4(OH)2). Changes in the color, gloss and hardness of the samples have been determined according to ASTM D 2244-2, ASTM D 2240 and EN ISO 2813 standarts. Research result shows that; weathering conditions have a reducing effect on color, gloss and hardness values while bleaching process following the weathering conditions has an increasing effect on values. In general, application of S4 solution group can be suggested to restore the color, gloss and hardness problems with bleaching process in wooden material exposed to weathering conditions.Keywords: Weathering conditions, bleaching, hardness, gloss, color measurement, restoration