Effects of Aqueous Ammonia Vapor on the Color and Chemical Structure of Robinia pseudoacacia and Oak Woods

Agata Stachowiak-Wencek, Monika Bartkowiak, Magdalena Zborowska, Jan Bocianowski


Aqueous ammonia vapors were found to affect the color and structure of oak (Quercus L.) and Robinia pseudoacacia L. woods. The modification process was performed using 5% or 10% ammonia concentration at a temperature of 120 °C, 130 °C, or 140 °C. Wood mass and volume change coefficients were determined. The degree of wood discoloration was determined using the Commission Internationale de l’Eclairage (CIE) Lab system, and the changes to the chemical structure were determined using the Fourier transform infrared (FTIR) technique. The samples darkened due to the modification. They also became less red and less yellow. It was found that Robinia wood was more discolored. The total color change (ΔE*) of Robinia wood ranged from 39.0 to 41.9, and of oak wood ranged from 26.8 to 33.3. The L* and b* color coordinates had a significant effect on the ΔE. Analysis of variance showed that in most cases both the concentration of the aqueous ammonia solution and the process temperature alone did not cause significant differences in the colour of the wood (GenStat 18ed (VSN International 2015)). However, the interaction between concentration and temperature was important. Analysis of wood structure via FTIR showed that during the applied treatment, wood underwent chemical changes and that the effects were different in the compared species.


Ammonia treatment; Oak; Robinia pseudoacacia; CIE L*a*b* system; FTIR

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