Archives de catégorie : Last Papers

Colorimétrie des bois – Diversité et complexité

Brémaud Iris, Cardon Dominique, Backes Bernadette, Cabrolier Pierre, Guibal Daniel, Langbour Patrick

Colorimétrie des bois: Diversité du matériau et complexité de son apparence.

CoRé (Conservation/Restauration, Revue de la SFIIC : Section Française de l’Institut International de Conservation), (2021) CoRé NS 1 :61-84

(Présentation de la revue sur le site de la SFIIC) / (Lien vers le N°1 de CoRé Nouvelle Série)

Exploring colors from the past in the steps of eighteenth-century dyers

Cardon Dominique, Brémaud Iris, Quye Anita, Balfour Paul Jenny

Exploring colors from the past: in the steps of eighteenth-century dyers from France and England.

The Textile Museum Journal (2020) 47:9-28

DOI: 10.7560/TMJ4702

Abstract: This paper presents some aspects of the contribution to the history of colors and dyeing technology to be expected from the comprehensive study of a rare type of historical document, which was not published and exploited until recently. It describes and compares several early– to mid–eighteenth century manuscripts of dye books or treatises on dyeing from England and France, having in common an essential feature: all are illustrated with scores of samples of dyed wool fabric. The French sources are the Memoirs on Dyeing of two dyework owners in wool broadcloth–producing centers in Languedoc in southern France. The English sources belong to the Crutchley Archive and consist of the dye books of a family-run dyed wool fabric business in Southwark, London. In this paper, the authors first present the respective color gamuts of the French dyers and their contemporary colleagues in London. The study is based on correlations between the color names given to the samples in the documents, the corresponding dye recipes, and the chromatic specifications of the samples that were obtained through colorimetric measurements and expressed in the CIE L*a*b* and CIE LCh° systems of color description. Madder red is then proposed as a case study for comparisons of the dyeing processes and resulting chromatic effects in the English and French sources.

Destabilisation in vibrational properties of wood when changing humidity

Brémaud Iris and Gril Joseph

Transient destabilisation in anisotropic vibrational properties of wood when changing humidity .

Holzforschung Ahead of Print. (2020)


Abstract: Moisture changes cause transient effects in various polymeric materials. In wood, they are mainly documented in semi-static or low-frequency domains and could explain various anomalies in wood behaviour, including the so-called mechano-sorptive effect. This article aimed at exploring and quantifying transient effects in wood vibrational properties, evidenced but in few publications. A series of 65 experiments on spruce and maple, in longitudinal (L) and radial (R) directions, spanning many humidity trajectories, were monitored through time (1–7 weeks) after step-change in relative humidity (RH). Changes in dimensions and specific dynamic modulus of elasticity (E′/γ) closely followed change in moisture content (MC). But the damping coefficient (tanδ) always increased (whether MC increased or decreased) within first hours/days, before slowly re-decreasing. This was quantitatively analysed by subtracting equilibrium moisture content (EMC) dependence from the global changes in tanδ, which simultaneously expressed destabilisation, followed by physical ageing (a slow process towards approaching equilibrium). For small EMC steps, the amplitude of destabilisation in L tanδ exceeded changes due to EMC dependence. Destabilisation was of similar importance relative to L or to R tanδ, while R tanδ showed much (2−4×) stronger EMC dependence. Amplitude of destabilisation increased with wider RH/EMC-steps (and faster sorption rates). Within an experiment, maximum destabilisation occurred nearly concomitantly with maximum sorption rate. Equilibrium was usually reached in MC, even within one week, but seldom in tanδ, even after several weeks. Results suggested that: (i) drying caused similar amplitudes of destabilisation, but that occurred sooner, and recovered faster, than humidifying; (ii) small RH-steps caused relatively smaller amplitudes of destabilisation, but that occurred later, and spanned over longer time before recovering equilibrium, than wide RH-steps. Some possible hypotheses are introduced to explain the observed phenomena. These phenomena also have important practical consequences in real-life wood uses and, particularly, in the design of experimental protocols

Keywords: Anisotropy; damping by internal friction; destabilisation by moisture sorption; dynamic mechanical properties; physical ageing; transient effects; viscoelastic vibrational properties .

Moisture content dependence of vibrational properties of wood

Brémaud Iris and Gril Joseph

Moisture content dependence of anisotropic vibrational properties of wood at quasi equilibrium: analytical review and multi-trajectories experiments .

Holzforschung Ahead of Print. (2020)


Abstract: This article aims at providing a synthetic view of the equilibrium moisture content (EMC) dependence of wood vibrational properties (i.e. dynamic mechanical properties in the audio-frequency range), including specific dynamic modulus of elasticity (E′/γ) and damping coefficient expressing internal friction (tanδ). A series of multi-trajectories experiments was designed to complete an analytical review. Literature indicates that: (1) in longitudinal (L) direction, the EMC dependence of E′/γ shows a very consistent shape (rather linear) between studies, while its shape is non-linear for tanδ and varies significantly between studies; (2) EMC dependence of tanδ is rather well documented in the L direction, in adsorption, for softwoods, but data covering EMC dependence in both L and other anisotropic directions, and sorption hysteresis, are still scarce. Experiments were conducted on a softwood (spruce) and a hardwood (maple), in L and radial (R) directions, in full adsorption from oven-dry state, full desorption from water-saturated state, and relative humidity (RH) loops without extreme conditioning. Measurements were made at conditions considered “at equilibrium” and some were monitored through time. Results indicated that tanδ was much more (×3) sensitive to EMC differences than E′/γ. R properties, especially tanδ R, were much more (×2–3) sensitive than L properties – resulting in strong increase of anisotropy with increasing EMC. In L direction, differences due to EMC remained moderate compared to the natural variability of wood for E′/γ, while for tanδ the EMC-induced changes were at least equal to natural variability in high-grade spruce. Vibrational properties did exhibit a hysteresis as a function of RH, but very little hysteresis as a function of EMC. The tanδ-EMC relation strongly depended on the actual time of stabilisation after reaching EMC. A related paper will address the transient, out of equilibrium effects of changing moisture conditions on the vibrational properties of wood.

Keywords: Anisotropy; damping by internal friction; equilibrium moisture content dependence; sorption history; specific dynamic modulus of elasticity; viscoelastic vibrational properties .

Mild hygrothermal treatment and physical-vibrational properties of spruce

Karami Elham, Bardet Sandrine, Matsuo Miyuki, Gaff Milan, Brémaud Iris and Gril Joseph

Effects of mild hygrothermal treatment on the physical and vibrational properties of spruce wood .

Composite Structures, 2020, 253, pp.112736

Link to the authors’ version

Abstract: Spruce wood specimens were treated under mild temperatures 130°C and 150°C and different relative humidity from 0% to 25%. EMC reduced significantly for all the treatments. Weight loss (WL) increased insignificantly while the colour parameter, L*, decreased dramatically. Tanδ reduced significantly while the E/d has increased. After reconditioning, the partially reversibility has been achieved for EMC, tanδ and E/d. But, still an irreversible changes remains, which suggested being due to the chemical changes in wood polymers. While reversible changes has been resulted from the annealing of amorphous polymers. Since, the mild hygrothermal treatment applied to the specimens coincided with no significant WL, there was no obvious damage in wood structure while the irreversible changes present an improvement in vibrational properties by decrease in damping (tanδ), which could be due to the intermediate relative humidity of the treatment.

Keywords: mild treatments, weight loss, colour parameter, reversible effects, reconditioning, damping .


Revisiting the notion of “resonance wood” choice: a de-compartementalised approach

Newly published Book Chapter:

Carlier Capucine, Alkadri Ahmad, Gril Joseph, Brémaud Iris (2018).

Revisiting the notion of “resonance wood” choice: a decompartementalised approach from violin makers’ opinion and perception to characterization of material properties’ variability.


pp119-141, In: Wooden Musical Instruments: Different Forms of Knowledge (Book of End of WoodMusICK COST Action FP1302), Pérez, M. A. & Marconi, E. (eds.). Philarmonie de Paris.

Abstract: This work aims to improve our understanding of the resonance wood and to investigate the interactions between their physical-mechanical properties, natural variability, and the violin makers’ methods for choosing their materials. In order to identify the luthiers’ practices and opinions, a socio-technical survey was conducted. Physical, vibrational, and visual/structural characteristics of the resonance wood obtained from several provenances with a variety of quality grades were also determined. Finally, these two approaches were completed by a psychosensory evaluation to compare the measurements that we have conducted with the evaluation results made by the violin makers.

Wavy maple anatomy and anisotropic vibrational properties

Alkadri Ahmad, Carlier Capucine, Wahyudi I, Gril Joseph, Langbour Patrick, Brémaud Iris.

Relationships between anatomical and vibrational properties of wavy Sycamore Maple.

IAWA Journal 39(1) : 63-86. (2018)


Abstract: Sycamore maple (Acer pseudoplatanus L.) is a wood species particularly known for its wavy grain figure and its high-value utilization among luthiers and craftsmen for making musical instruments or furniture. In this study, the anatomical and physical-acoustical characteristics of its wood, taken from different trees with various surface figures, were characterized. Vibrational mechanical measurements were conducted taking into account radial and longitudinal directions and local variations. Waviness parameters were quantified on split blocks, and anatomical properties such as microfibril angle and ray dimensions were measured using light microscopy. Results provide a complete dataset on the properties of sycamore maple along a gradient of the wavy figure. Through statistical analysis, significant correlations were found between the measured parameters, particularly between the waviness and microfibril angle, and between the anatomical features and the specific modulus of elasticity and damping by internal friction of the wood in the longitudinal direction. Anisotropy was found to be very low but was not satisfactorily explained by the studied anatomical features. Prospects for future studies on the wavy figure are discussed.

Keywords: Acoustic properties, anisotropy, damping, microfibril angle, specific modulus of elasticity, rays, wavy grain.