This study was aimed to investigate the effect of steam treatment before densification on leachability and dimensional stability of nanocopper impregnated poplar (Popolus alba). Wood samples were impregnated with nanocopper suspension (200 and 400 ppm) for 20 minutes under 4 bar pressure. Steaming process was done before densification at 150°C for 2 hour. Radial densification (33%) was done consequently at 170°C for 30 min. Spring back (spontaneously after press and after 15 and 30 days), long term water absorption (LWA) and radial swelling (LRS) after (2hrs, 24hrs,48hrs, 1 week, 2 weeks, 3 weeks, 4 weeks and 8 weeks) soaking in water were measured and all data analysed statistically. Leaching test was carried out according to EN84, 1997. Results showed steaming and densification had negative effect on nanocopper fixation in wood samples and nanocopper leaching significantly increased in steamed densified samples. The highest leaching values belonged to 400ppm impregnated samples steamed and densified. 200ppm impregnated densified samples had significant decrease in copper leaching comparing to steamed densified samples but the values were still over the safety limit. In non densified samples impregnated with both concentrations of nanocopper, the leaching values were at the safety limit. Highest spring back values were seen after 15 and 30 days at either concentration of nanocopper. The least water absorption was seen in steamed densified samples whereas the least radial swelling was seen in non-densified samples. This study proves that nanocopper impregnated densified or steamed densified poplar are not suitable for humid condition where wood is in contact with ground or water.

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