Alum, with glycerol and various surface coatings, was routinely used during the early 1900’s as a conservation treatment for archaeological wood to prevent shrinkage and to impart strength. A history of the method and its associated problems is outlined. A survey assessing the condition of alum-treated wood according to the presence or degree of salt precipitation, surface flaking, cracking and pulverization was undertaken on the archaeological collection of The Swedish History Museum in Stockholm. The majority of artefacts were found to exhibit on-going deterioration, loss of material, and a need for consolidation in the event of re-conservation.