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Classical guitar necks were submitted to 40, 65 and 80% relative humidity (RH) during time periods ranging from 24 h to several months, and moisture-induced deformations were observed. Different types of classical guitar necks were investigated in terms of structure and reinforcement. The influences of the wood species and the neck reinforcements on the moisture content (MC)-induced deformation were in focus. First, before humidity exposure in the climatic chamber, the relative positions of three points marked on each sample were measured with a control ruler and noted. After exposure, the displacement of the reference points on the samples were verified periodically. The differences between the measurements in different stages and reference positions were calculated, resulting in relative displacement data of the measured points. During the experiments, the MC of the sample was monitored by weighing. The variation of RH leads to dimensional instability and moisture-induced stresses of the guitar necks, which affect the acoustic quality of a guitar. Steel enforcement of the guitar neck improves this situation. [ABSTRACT FROM AUTHOR]

Small wooden samples of fir (Abies alba Mill.) and beech (Fagus sylvatica L.) were chemically modified by citric acid (CA) as non-formaldehyde cross-linking system reagent and cured by convection heating at three different temperature regimes. Two different CA solutions were used, one with NaH2PO2 and the other with NaH2PO4 as a catalyst. The dimensional stability of the modified wood was determined by the anti-swelling efficiency (ASE) using the water soak/oven dry method. Almost equally large improvement of dimensional stability of wood was attained using NaH2PO4 as when NaH2PO2 was applied as a catalyst.

The aim of this work was to investigate the effect of heat treatment on some physical and mechanical properties of three timber species namely Oak ( Tabebuia rosea), Teak ( Tectona grandis) and Chanul ( Humiriastrum procerum). Samples were exposed to different temperature levels: 130, 150, 180 and 210 °C for periods of 2, 4 and 8 h. The swelling values and moisture absorption of control and heat treated samples were evaluated after water immersion in 2 and 24 h. The hardness in wood was determined according to the Janka's hardness method of the ball in three sectional planes. Stereoscopy and scanning electron microscopy were used to determine certain characteristics of cell wall like distortions related to variation of the different heat treatment conditions. Energy dispersive X-ray analysis showed some decreases in carbon content after heat treatment, and thermogravimetric analysis indicated the removal of lignin after 180 °C. The modulus of rupture, elastic modulus and proportional limit strength were also analyzed from flexural behavior. It was demonstrated that dimensional stability of three wood species was enhanced after heat treatment. [ABSTRACT FROM AUTHOR]