Study of the Effects of Tannin Impregnation to Spruce Wood

This thesis explores the influence of tannin concentration and cross-linking agents on the impregnation, leaching resistance, mechanical performance, and color stability of Norway spruce (Picea abies). Chestnut tannin solutions at 10%, 20%, and 30% were applied, both alone and in combination with glyoxal, hexamine, or furfural, to assess their effectiveness as sustainable wood treatments. The findings indicate that a 20% tannin solution achieved the most efficient impregnation, balancing uptake and viscosity. Among the hardeners, furfural consistently delivered the strongest results, enhancing fixation, leaching resistance, hardness, and color stability. Glyoxal provided moderate improvements, while hexamine performed poorly under unadjusted pH conditions, though its potential under optimized formulations remains a promising avenue for future research. Across all treatments, tensile strength was preserved, confirming that tannin modification does not compromise structural integrity. Colorimetric analysis further revealed that tannin–furfural treatments resisted uneven darkening and ultraviolet degradation, thereby improving both durability and aesthetic stability. Collectively, these results highlight tannin–furfural systems as particularly promising bio-based alternatives to conventional preservatives, aligning material performance with environmental responsibility.