Chosen properties of oak wood immersed for 6 months in the Baltic Sea

Changes of physical and chemical properties, mass loss and susceptibility of oak wood to decay caused by Basidiomycetes fungi were assessed after wood samples had been taken out of the sea within the framework of MACHU project. Test samples of oak wood of the dimensions of 250 × 10 × 10 mm were placed in coastal waters of the Baltic Sea at the area of medieval seaport in Puck and in waters of the Gdansk Bay at the same longitude as Orłowo (near the wreck of Swedish warship Solen). The samples taken out of the sea were examined visually and described. Changes in mass of the samples, their bending strength and modulus of elasticity, compression strength along the grain, ability to decay caused by Trametes versicolor fungus, content of mineral substances and substances soluble in water, ethanol-benzene mixture and in 1-percent aqueous solution of NaOH, content of cellulose, lignin and pentosanes as well as pH of the wood were investigated. The properties of samples taken out of the sea after 6 months of immersion were compared with the properties of control twin samples of oak wood which had not been immersed. The results obtained so far indicate that noticeable, measurable changes in oak wood immersed in sea occur already in half a year since immersion, so observation of them may be useful for protection and monitoring of underwater archaeological objects.