As part of the EC-project "Improvement of a local preservation process for wood products with reduced environmental impact", TNO has performed a leaching test on L-joints treated with pills with boric acid (Defence corner), bifluorides (Woodpil 55) and TBTO (Woodcap). The L-joints were exposed in an adapted shower test during 10 days, using 70 liters of water per day. The experiment is designed to measure leaching under extreme service conditions. Spruce and pine, painted and unpainted L-joints were compared. In general leaching was the highest in spruce. The L-joints treated with boric acid pills showed the highest leaching, with very small differences between painted and unpainted L-joints. Leaching from fluoride and TBTO treated L-joints was even slightly higher than in painted L-joints. From these results it is suggested, that the active ingredients predominantly leach from the end grains in the open joint area of the timber. A higher water run off rate from longitudinal surfaces in painted L-joints could explain for the higher leaching rate in these samples

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