In spite of the general opinion that Scots pine sapwood is easy to impregnate considerable variations in treatability are reported. In order to study impregnation results of diverse Scots pine sapwood treated with increasing process times, Scots pine sapwood from two different predefined treatability groups was impregnated. A copper solution was used as impregnation agent in ten different vacuum pressure schedules. Pressure times increased from 15 min to 520 min. The results of this study confirm considerable variations in the treatability of Scots pine sapwood. Differences between easy to impregnate and refractory sample sets are visible for the different impregnation schedules. The impregnation results however depend on the indicator of treatment quality applied. The refractory sample set reaches higher solution uptakes after 180 min of pressure whereas the easy to impregnate sample set has a better penetration of the wood matrix for most of the impregnation schedules. Differences in the results are visible when comparing indicators of treatment quality based on solution uptake, ratio of filling and impregnation depth. The gravimetric method (uptake) can give a false impression of the impregnation result. It is important to be aware of these differences in treatability of the material and between different indicators of treatment quality. The results can be important for the impregnation industry as they show that by sorting for easy to impregnate material, process times could be significantly reduced and simultaneously lead to more homogeneous impregnation results and smaller within batch variations.

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