The correct impregnation of wood requires among other things a regular control of the concentration of the treating solution as this and/or its stoichometric composition can change as a result of the impregna-tion process and the treated wood. The preferential uptake of individual wood preservative components by the wood is of particular importance in this connection. Dipping and vacuum impregnation of wood specimens was carried out in laboratory studies, whereby the concentrations of chromium and copper in the impregnation solution were determined before and after impregnation. In addition to this, some specimens were segmented after fixation, analysed and the ratio of the active ingredients in dependence on their penetration depth was calculated. The ratio of the constituents in the solution after the impregnation process was shown to vary from that of the initial composition. Furthermore there was a striking deficit of chromium in comparison to copper in the areas of wood near to the surface, but an excess of chromium in deeper zones. This therefore results in a comparatively greater concentration gradient for chromium which causes the wood to absorb chromium to an increased degree. It can be deduced from these results that not only the density of the solution should be analysed after certain intervals of time, but also the stoichometric composition of the impregnation agent. Further investigations will be carried out as there remain a number of unanswered questions about the increased uptake of wood preservative components (e.g. when using other treating procedures or other wood preservatives without chromium).

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