In an optimized two-step treatment, first with low molecular weight then with high molecular weight PEG, large archaeological, waterlogged oak timbers containing wood of varying quality can be stabilized to the same degree. The amount of PEG necessary for maximum stabilization depends on the state of degradation of the wood and corresponds to about 50% of the maximum water content for low molecular weight PEG in slightly degraded wood, and 66% of the maximum water content for high molecular weight PEG in heavily degraded wood.