The Deformometric Kit: A method and an apparatus for monitoring the deformation of wooden panels

Uzielli, Luca; Cocchi, Linda; Mazzanti, Paola; Togni, Marco; Jullien, Delphine; Dionisi-Vici, Paolo

doi:10.1016/j.culher.2012.03.001

Cited by 17 publications

(10 citation statements)

References 2 publications

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“…The panel is monitored with 3 Deformometric Kits (DKs) [8] glued at the back of boards 2 and 3: DK1 and DK2 are placed in the upper and lower parts of board 2 respectively, DK3 in the lower part of board 3, horizontally aligned with kit 2 (Figure 3-a). The locations of the DKs have been chosen on undamaged parts of the boards, crossing no wood cracks nor separations between the two columns, otherwise the instrumental reading of the DK would have taken into account simultaneously both the deformation of the support and the movements of the crack lips without the possibility of decoupling the two contributions.…”

Section: -4 Local Strain and Cupping Measurementmentioning

confidence: 99%

“…The locations of the DKs have been chosen on undamaged parts of the boards, crossing no wood cracks nor separations between the two columns, otherwise the instrumental reading of the DK would have taken into account simultaneously both the deformation of the support and the movements of the crack lips without the possibility of decoupling the two contributions. The DK is an instrument that allows the continuous local monitoring of the deformation dynamics of the wooden panel with respect to both the external forces applied and the hygroscopic coactions: in other terms, it allows to understand the reactivity of the panel, the evolution of the cupping over time, and under some hypotheses (detailed in [8], with the operating principles) the deformation of the panel in the proximity of the device. It consists (…”

Section: -4 Local Strain and Cupping Measurementmentioning

confidence: 99%

“…The weight was determined using a balance placed inside the show case. Changes in the shape deformation and the panel strain due to the climatic variations, were observed using two methods: three sets of displacement transducers fixed on the back face of the panel measured local curvatures [8] while a non-contact optical technique, mark tracking, was used for the assessment of the entire surface of the panel [9][10] [11] [12]. The correlation between local and whole-field measurements will be verified.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of the hygromechanical behaviour of a historic painting on wooden panel : devices and measurement techniques

Dupre

Jullien²,

Uzielli

et al. 2020

Journal of Cultural Heritage

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This article describes the experimental devices and the processes used to study the hygromechanical behaviour of a historic painted wooden panel (La Sainte Trinité couronnant la vierge, 1516, anonymous, Fabre Museum of Montpellier). A climate showcase was designed for in-museum use, with two glasses allowing visitors as well as scientists to observe both sides simultaneously. The evaluation of the hygroscopic behaviour was done by measuring relative humidity (RH), temperature and variations of panel weight. Variations of panel shape, strain and curvature were observed by two methods: locally with three pairs of displacement transducers fixed on the rear face, and over the entire panel surface by a non-contact optical technique, stereo mark tracking, used simultaneously on both faces. The correlation between local and whole-field measurements was very good. Continuous monitoring (several data per hour over three years) was required to observe the behaviour of the panel during imposed climate variations. The first test, detailed in this paper, was performed before frame removal and panel restoration. It consisted in a stabilization of the panel at 52% RH during 2 months and an increase to 63% RH during 3 months. The small amount of total mass variations, from 31.980 kg to 31.910 kg at 52% RH and 32.088 kg at 63% RH, could not be explained without taking into account the phenomenon of sorption hysteresis. The whole field relief measurement exhibited a concave shape with a maximum amplitude of 16 mm. It showed that shape deformation, ie out-of-plane displacement, was convex bending with a maximum deflection of 1.5 mm and a maximum strain of 0.1 %. Comparable local data had been obtained by the optical and DKs methods. DKs results were ten times more accurate than optical ones. The horizontal strain exhibited a global shrinkage during initial stabilization and a global swelling during RH increase. Heterogeneity of the strain field can be related to the cracks observed on the back face, and to the glued crossbeams. Assuming a linear relationship between swelling and moisture content, we expected, for a 0.6% increase of moisture content, a radial strain of 0.10% and a tangential strain of 0.22%. These results are higher than the ones measured, which can be explained by the cross bars glued on the boards and the cracks. This comparison will be continued for the next stages (crossbars removal, panel restoration).

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Section: -4 Local Strain and Cupping Measurementmentioning

confidence: 99%

Section: -4 Local Strain and Cupping Measurementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental study of the hygromechanical behaviour of a historic painting on wooden panel : devices and measurement techniques

Dupre

Jullien²,

Uzielli

et al. 2020

Journal of Cultural Heritage

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“…The replicas were vapour-proofed with rubber latex on the front face, simulating a protective varnish, as well as on the four lateral edges to eliminate edge effects. Replica "A" was connected by means of springs to an auxiliary support and equipped with 3 "deformometric kits" (DK) [4,7,[13][14][15][16] to monitor the deformation (cupping and swelling/shrinkage) over time. Additionally, each spring was also equipped with a displacement transducer to monitor its deflection, and hence the force between the panel and the support acting on it.…”

Section: Fig 3 -Two Replicas Of a Portion Of The Triptych With Auximentioning

confidence: 99%

Mechanical study of a support system for cupping control of panel paintings combining crossbars and springs

Marcon

Mazzanti

Uzielli

et al. 2012

Journal of Cultural Heritage

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Special Issue on Wood Science and ConservationInternational audienceSpring mechanisms have been developed, since late 1970s, to provide some freedom of deformation to the wooden supports of paintings; however, no scientific method is up to now available for optimizing their design parameters. This article deals with theoretical and experimental work on the replica of an actual wooden support restored in a Florentine laboratory. A model is developed to describe its deformational behaviour after an auxiliary support has been applied by means of springs. The main outcome of such a research, still on-going, is a numerical model verified experimentally, enabling a restorer to choose the most appropriate mechanical parameters for springs in order to obtain the desired control of deformations and stresses produced by the expected environmental conditions

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“…An alternative approach is to directly monitor the dimensional changes of wood using sensors. A well-known method is the deformometric kit (DK) that is developed to monitor the deformation of panel paintings [17,18]. The DK measures both the panel's swelling and shrinking behaviour as its distortion (cupping).…”

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confidence: 99%

Real-Time Wood Behaviour: The Use of Strain Gauges for Preventive Conservation Applications

Anaf

Cabal

Robbe

et al. 2020

Sensors

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Within the heritage field, the application of strain gauges on wood surfaces is a little-explored but inexpensive and effective method to analyse the environmental appropriateness of rooms for the wooden heritage collections they contain. This contribution proposes a wood sensor connected to a data logger to identify short moments with an elevated risk of harm. Two experiments were performed to obtain insights pertaining to the applicability of wood sensors to evaluate preservation conditions. (1) The representativeness of strain gauges on dummies was tested for their use in evaluating the preservation conditions of a range of wooden objects exposed to the same environment. For this, three situations were mimicked: a bare wood surface, a wood surface covered with a preparation layer, and a wood surface covered with a preparation and varnish layer. (2) The usability of strain gauges to monitor the wood behaviour in real-time measurements was tested with a monitoring campaign of almost two years in a church where a new heating system was installed. The results of both experiments are promising, and the authors encourage a broader application of strain gauges in the heritage field.

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The Deformometric Kit: A method and an apparatus for monitoring the deformation of wooden panels

Cited by 17 publications

References 2 publications

Experimental study of the hygromechanical behaviour of a historic painting on wooden panel : devices and measurement techniques

Experimental study of the hygromechanical behaviour of a historic painting on wooden panel : devices and measurement techniques

Mechanical study of a support system for cupping control of panel paintings combining crossbars and springs

Real-Time Wood Behaviour: The Use of Strain Gauges for Preventive Conservation Applications

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