Mineralization of European oak with various ionic salt solutions to achieve an in situ precipitation of calcium oxalate

Thin specimens of European oak (Quercus spp.) with the dimensions of 4 x 20 x 50 mm3 were treated with various aqueous ionic salt solutions of calcium chloride, potassium oxalate and calcium acetate. Additionally, the oak was treated with combinations of calcium chloride and potassium oxalate, as well as calcium acetate and potassium oxalate with the aim to precipitate in situ the water insoluble salt calcium oxalate. The specimens were impregnated in an autoclave under pressure with the single compounds, as well in combinations in a two-step process, successively. The treatability of the oak was determined by means of the bulking coefficient and due to segment electron microscopy investigations. Possible precipitation to calcium oxalate in situ in oak was determined by ATR-FTIR measurements and a changing moisture uptake after the two-step impregnation serves as a further indicator for a calcium oxalate precipitation. The study shows, that thin oak lamellas can be impregnated with the investigated solutions and additionally, the data obtained in this study indicating that there is an in situ precipitation to the wanted water insoluble salt calcium oxalate and the corresponding by-product.