Studies on the dynamics of pressure changes in wood during impregnation revealed no significant effect of fast pressure changes for green spruce as used by OPM (IRG/WP/3615). The following experiments were carried out on several hundreds of spruce palisades to examine the modification of single procedure parameters of common use OPM and to record the effects on the impregnation result with the aim of simplifying the energy and cost expensive technique, retaining the same or possibly an improved treatment quality. The samples were endsealed and impregnated with CCB (4%), their actual effective substances being defined by AAS at the beginning and at the end of the treatment. Generally, programme variants with several pressure changes, independent of their number, duration and dynamics, resulted in a better penetration of the sapwood than programmes where a constant pressure was used. Fast pressure alternation within a few seconds did not result in a noticeable better impregnation quality. A dynamic change of the phase lengths and of the distribution quotient for pressure and vacuum respectively atmospheric pressure did not improve the treatment result. Sapwood moisture content between 100 and 180% are optimal preconditions for a good treatment quality.

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