The Effects of CO2 Laser Irradiation on Color and Major Chemical Component Changes in Hardwoods

Kubovský, Ivan; Kačík, František; Veľková, Veronika

doi:10.15376/biores.13.2.2515-2529

“…Spruces aged for 200–400 years exhibit decreased infrared absorption at 1735 cm −1 (Supporting Information Figure S13–S15), caused by hemicellulose deacetylation [21a, 28] . This becomes even more evident in aged softwood taken from millennium‐old Chinese zithers (Supporting Information Figure S16).…”

Section: Resultsmentioning

confidence: 99%

Materials Engineering of Violin Soundboards by Stradivari and Guarneri

Su

¹

,

Chen

²

,

Chung

³

et al. 2021

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We investigated the material properties of Cremonese soundboards using a wide range of spectroscopic, microscopic, and chemical techniques. We found similar types of spruce in Cremonese soundboards as in modern instruments, but Cremonese spruces exhibit unnatural elemental compositions and oxidation patterns that suggest artificial manipulation. Combining analytical data and historical information, we may deduce the minerals being added and their potential functions—borax and metal sulfates for fungal suppression, table salt for moisture control, alum for molecular crosslinking, and potash or quicklime for alkaline treatment. The overall purpose may have been wood preservation or acoustic tuning. Hemicellulose fragmentation and altered cellulose nanostructures are observed in heavily treated Stradivari specimens, which show diminished second‐harmonic generation signals. Guarneri's practice of crosslinking wood fibers via aluminum coordination may also affect mechanical and acoustic properties. Our data suggest that old masters undertook materials engineering experiments to produce soundboards with unique properties.

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“…Decreasing of L* means wood color darkening, which may be caused by the degradation of hemicellulose and movement of extractives. Kubovský et al also reported that the decrease of L* value in wood surface was closely related to the degradation of hemicellulose [24]. The decreasing of b* value describes the trend of the wood surface towards bluish, which can be explained by the reduction of a tonality component in color and a slight decreasing value of color saturation [26].…”

Section: Figmentioning

confidence: 94%

“…Previous studies reported that the NaOH/Na 2 SO 3 solution system can dissolve the extractives in wood and can also degrade hemicellulose and lignin in wood cell walls [15]. The degradation of hemicellulose and lignin was another reason for wood color changes in the densified wood [24]. Due to the polysaccharide composition of hemicellulose, various saccharic acids are gradually generated through the peeling reaction started from the reducing terminal group of polysaccharides in alkaline environment.…”

Section: Figmentioning

confidence: 99%

Fabrication of densified wood via synergy of chemical pretreatment, hot-pressing and post mechanical fixation

Shi

¹

,

Peng

²

,

Huang³

et al. 2020

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Wood densification can improve the strength of low density wood species and extend wood product applications. To enhance the wood compressive quality, chemical pretreatments for pristine wood have widely been used. Densified Abies wood was fabricated by combining NaOH/Na 2 SO 3 solution treatment, hot-pressing and post mechanical fixation. The appearance, color, chemical composition, and physiology and mechanical properties before and after the densification treatment were examined by the colorimeter, FTIR and mechanical testing machine, respectively. Surface color of Abies wood was changed obviously after the densification. The values of brightness L* and b* decreased but the value of a* showed a slight increase in the densified wood. FTIR results confirmed that the color changes can be explained by the degradation of hemicellulose and lignin in wood cell walls and migration of extractives during the densification process. Sufficient removal of wood polymers resulted in the average compression ratio of about 80% in the radial direction of the natural wood. The density of densified wood increased with the wood thickness up to 1.227 g cm −1 , accounting for a 169% increase compared to that of the pristine wood. Modulus of rupture (MOR) and modulus of elasticity (MOE) in the thickness direction of densified wood also markedly enhanced. Degradation of polymers in wood cell walls also was reconfirmed by the difference of fracture interface. All the results suggested that the densified softwood can be easily fabricated using the proposed method and the new densified softwood can be appropriately used as interior decoration materials.

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“…Spruces aged for 200–400 years exhibit decreased infrared absorption at 1735 cm −1 (Supporting Information Figure S13–S15), caused by hemicellulose deacetylation. [ 21a , 28 ] This becomes even more evident in aged softwood taken from millennium‐old Chinese zithers (Supporting Information Figure S16). Interestingly, Stradivari and Guarneri spruces uniquely exhibit increased absorption around 1710 cm −1 (Figure 3 b ), implicating the generation of ketones or carboxylic acids via oxidation.…”

Section: Resultsmentioning

confidence: 97%

Materials Engineering of Violin Soundboards by Stradivari and Guarneri

Su

¹

,

Chen

²

,

Chung

³

et al. 2021

View full text Add to dashboard Cite

We investigated the material properties of Cremonese soundboards using a wide range of spectroscopic, microscopic, and chemical techniques. We found similar types of spruce in Cremonese soundboards as in modern instruments, but Cremonese spruces exhibit unnatural elemental compositions and oxidation patterns that suggest artificial manipulation. Combining analytical data and historical information, we may deduce the minerals being added and their potential functions—borax and metal sulfates for fungal suppression, table salt for moisture control, alum for molecular crosslinking, and potash or quicklime for alkaline treatment. The overall purpose may have been wood preservation or acoustic tuning. Hemicellulose fragmentation and altered cellulose nanostructures are observed in heavily treated Stradivari specimens, which show diminished second‐harmonic generation signals. Guarneri's practice of crosslinking wood fibers via aluminum coordination may also affect mechanical and acoustic properties. Our data suggest that old masters undertook materials engineering experiments to produce soundboards with unique properties.

show abstract

The Effects of CO2 Laser Irradiation on Color and Major Chemical Component Changes in Hardwoods

Cited by 9 publications

References 0 publications

Materials Engineering of Violin Soundboards by Stradivari and Guarneri

Materials Engineering of Violin Soundboards by Stradivari and Guarneri

Fabrication of densified wood via synergy of chemical pretreatment, hot-pressing and post mechanical fixation

Materials Engineering of Violin Soundboards by Stradivari and Guarneri

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