Papers by Michal Lukomski
Experimental Techniques, 2018
The paper presents an experimental procedure based on micro-scratching to detect stresses in the ... more The paper presents an experimental procedure based on micro-scratching to detect stresses in the ground layer of panel paintings. The method relies on the fact that cracking of the material during a micro-scratching test is the outcome of a combination of local force applied by an indenter and the stresses present in the material. The critical normal load at which damage appears during the test has a strong correlation with the stress in the material. The method, although not providing absolute values of stress, is sensitive to stress magnitude and direction, only micro-destructive, and attractive for monitoring stress changes caused by relaxation processes also in multi-layer materials. The presented tests were performed on artistic materials for which information on stress relaxation is particularly important when developing strategies for their storage and transportation.
Measuring adhesion between heterogeneous samples continues to be problematic for the cultural her... more Measuring adhesion between heterogeneous samples continues to be problematic for the cultural heritage field, which typically relies on a macroscale destructive tape test method. As an alternative technique, atomic force micros-copy (AFM) is employed in this study to capture nanomechanical information on adhesion from force-displacement curves. In the context
Acoustic emission (AE) is a method with great potential for monitoring the development of micro-d... more Acoustic emission (AE) is a method with great potential for monitoring the development of micro-damage in objects exposed to the potentially harmful conditions of temperature (T) and relative humidity (RH). It allows one to directly record damage growth while changes remain invisible to those caring for the collection, as opposed to monitoring and inferring damage indirectly due to undesired interactions with local climates or waiting for visible damage to develop. As a consequence, AE can be used to record environmentally-induced physical changes directly in historic materials and, hence, can support the assessment of strategies for the indoor climate management of museums. However, applying AE to museum collections requires specific measures to deal with issues such as the uniqueness and fragility of the monitored objects, the diversity of construction materials and the measurement of signals in an often noisy environment. Systematic tests of the propagation and attenuation of AE signals in wood were performed to better understand the monitoring results in terms of damage location and to assess the ability of various high-pass filters to reduce the background noise. This paper offers an insight into monitoring methodologies for wooden art objects to effectively manage the museum climate.
The drying shrinkage accumulation from exposure of freshly-prepared gesso layers to relative humi... more The drying shrinkage accumulation from exposure of freshly-prepared gesso layers to relative humidity (RH) cycles was determined to elucidate the mechanism of craquelure pattern formation on panel paintings. The progresive drying shrinkage of the gesso is observed only under the cycles going to high RH levels which bring about transitions from brittle to ductile state of the material. The first incidence of fracture on the gesso layers occurred after a limited number of cycles ranging between a few and 100 for a range of layer thickness between 0.5 to 1 mm. The craquelure patterns stabilized also after a limited number of cycles (30 for the 1 mm thick layer). Upon increase of the gesso layer thickness, the strength of the layer is reduced and the spacing of shrinkage fractures increases. The study demonstrated that craquelure patterns, mimicking historical ones, can be realistically produced in laboratory conditions. Such studies would provide useful information for preparing specimens simulating historic panel paintings and would inform the current efforts on automatic, computer-aided classifications of crack formations on paintings.
Digital Speckle-Shearing-Pattern Interferometry (DSSPI) combined with Digital Speckle-Pattern Int... more Digital Speckle-Shearing-Pattern Interferometry (DSSPI) combined with Digital Speckle-Pattern Interferometry (DSPI) were used to document the state of preservation of 8th to 14th century wall paintings of Christian Nubia. The original plasters of the paintings were multilayer inhomogeneous structures cracked in some parts. They were removed from the cathedral in Faras, Sudan, between 1961 and 1964 as part of efforts to rescue archaeological works threatened by flooding and are now held in the collection of the National Museum in Warsaw. Delaminated areas in surfaces of the paintings were detected by inducing surface vibrations with a sonic wave of varying frequency emitted from a loudspeaker. DSPI allowed the size of the areas and vibration resonant frequencies to be characterized,
of climate-induced damage in historic textiles', Strain, ABSTRACT: Eleven wool and silk historic ... more of climate-induced damage in historic textiles', Strain, ABSTRACT: Eleven wool and silk historic textiles and two modern artist's canvases were examined to determine their water-vapour adsorption, moisture dimensional response and tensile behaviour. All the textiles showed a similar general pattern of moisture response. A rise in ambient relative humidity (RH) from dry conditions produced expansion of a textile until a certain critical RH level after which a contraction occurred to a greater or lesser degree depending on the yarn crimp and the weave geometry. The largest expansion recorded between the dry state and 80% RH was 1.2 and 0.9% for wool and silk textiles, respectively.
Eleven wool and silk historic textiles and two modern artist's canvases were examined to determin... more Eleven wool and silk historic textiles and two modern artist's canvases were examined to determine their water-vapour adsorption, moisture dimensional response and tensile behaviour. All the textiles showed a similar general pattern of moisture response. A rise in ambient relative humidity (RH) from dry conditions produced expansion of a textile until a certain critical RH level after which a contraction occurred to a greater or lesser degree depending on the yarn crimp and the weave geometry. The largest expansion recorded between the dry state and 80% RH was 1.2 and 0.9% for wool and silk textiles, respectively. The largest shrinkage of 0.8% at high RH range was experienced by a modern linen canvas. Two potential damage mechanisms related to the moisture response of the textiles -stress building due to shrinkage of the textile restrained in its dimensional response and the fretting fatigue when yarns move with friction one against another -were found insignificant in typical textile display environments unless the textiles are severely degraded or excessively strained in their mounting.
Holzforschung, 2014
Scots pine (Pinus sylvestris L.) was subjected to relative humidity (RH) changes and the dynamic ... more Scots pine (Pinus sylvestris L.) was subjected to relative humidity (RH) changes and the dynamic strain field on the surface and in the bulk wood was monitored by digital speckle pattern interferometry (DSPI) and X-ray computed microtomography (μXCT) assisted by digital volume correlation (DVC). If a freely shrinking specimen was subjected to an RH decrement, earlywood (EW) and latewood (LW) at the surface layer were deformed in the opposite directions at the beginning of drying due to moisture gradient across the specimen. As a result, the surface and core behaved as independent sub-components, with the surface restrained in its response by the dimensionally unchanged core. With time, both LW and EW shrank as moisture content (MC) became uniform across the specimen. When an entire wood specimen was restrained from movement and desiccated in ambient RH, EW was stretched to compensate for the considerable shrinkage of LW. Knowledge about surface deformation at the annual ring level as a function of varying RH may be helpful to assess the risks associated with the damage of paint layers caused by fluctuations of ambient RH.
Studies in Conservation, 2014
The on-site monitoring of acoustic emission (AE) has allowed the direct tracing of climateinduced... more The on-site monitoring of acoustic emission (AE) has allowed the direct tracing of climateinduced crack propagation in an eighteenth century wardrobe displayed in the Gallery of Decorative Art in the National Museum in Krakow, Poland. The anti-correlation measuring scheme and frequency filtering allowed very low levels of physical damage to the wardrobe to be detected in spite of the high background noise typical of the museum environment. The total AE energy recorded during two years of monitoring corresponded to a fractured area of 12 mm 2 or a total crack propagation of 1.2 mm for two10 mm-thick panels. Although the total damage recorded was minute, correlation between the events of fracturing and falls in indoor relative humidity (RH) in winter due to insufficient humidification was evident. The risk of damage, expressed in terms of crack propagation, was quantified as a function of the magnitude of the RH falls of the duration compatible with the response time of the object. The data allows acceptable RH falls to be identified if a conservation professional or a curator selects a 'tolerable' yearly propagation of the fracture, in other words the progress of damage considered insignificant.
European Journal of Wood and Wood Products, 2013
Timber elements are major structural and architectural components in historic buildings, at the s... more Timber elements are major structural and architectural components in historic buildings, at the same time belonging to the category of materials vulnerable to degradation. The recovery of 150-year old timber beams from a roof of a historic building made possible the non-destructive investigation of their response to cyclic loading. The experimental study carried out using the acoustic emission technique provided evidence that historic wood shows the load memory known as the Kaiser effect. The effect was observed for different loading and unloading time windows. The observations open a new perspective for the determination of defects in wooden objects and constructions, important for assessing their possible structural instability.
Proceedings of the 3rd European Workshop on Cultural Heritage Preservation Bozen/Bolzano, Italy, 2013
Kraków is used in the summer period for cooling and dehumidification. To refine the process and p... more Kraków is used in the summer period for cooling and dehumidification. To refine the process and possibly reduce energy demand a series of simulations have been carried out. The main calculative tool was the WUFI®PLUS software, developed at the Fraunhofer-Institute for Building Physics, to model the hygrothermal performance of the multi-zone building.
Proceedings of SPIE Volume 8790, 2013
Technical development and practical evaluation of a laboratory built, out-of-plane digital speckl... more Technical development and practical evaluation of a laboratory built, out-of-plane digital speckle pattern interferometer (DSPI) are reported. The instrument was used for non-invasive, non-contact detection and characterization of early-stage damage, like fracturing and layer separation, of painted objects of art. A fully automated algorithm was developed for recording and analysis of vibrating objects utilizing continuous-wave laser light. The algorithm uses direct, numerical fitting or Hilbert transformation for an independent, quantitative evaluation of the Bessel function at every point of the investigated surface. The procedure does not require phase modulation and thus can be implemented within any, even the simplest, DSPI apparatus. The proposed deformation analysis is fast and computationally inexpensive. Diagnosis of physical state of the surface of a panel painting attributed to Nicolaus Haberschrack (a late-mediaeval painter active in Krakow) from the collection of the National Museum in Krakow is presented as an example of an in situ application of the developed methodology. It has allowed the effectiveness of the deformation analysis to be evaluated for the surface of a real painting (heterogeneous colour and texture) in a conservation studio where vibration level was considerably higher than in the laboratory. It has been established that the methodology, which offers automatic analysis of the interferometric fringe patterns, has a considerable potential to facilitate and render more precise the condition surveys of works of art.
Journal of Cultural Heritage, 2012
Painted wooden panels are multi-layered structures composed of wood, animal glue, gesso and paint... more Painted wooden panels are multi-layered structures composed of wood, animal glue, gesso and paints, in which the gesso layer is particularly vulnerable to humidity fluctuations due to the development of internal stresses and fracture. This study established experimentally a relationship between the strain magnitude leading to the first fracture of the gesso and the number of cycles at that strain, that is, the vulnerability of the gesso layer to fatigue damage. Specimens of single, wood panels coated with gesso were subjected to cycles of mechanical stretching and compression to imitate dimensional changes induced in the system by repetitive fluctuations of relative humidity (RH). The development of cracks in the gesso layer was monitored using a laser speckle decorrelation technique. Numerical modelling was used to calculate the amplitude of sinusoidal RH cycles which are allowable so as not to exceed the critical mismatch between the climate-induced responses of the unrestrained wood panel and the gesso layer respectively, which would lead to the first fracture of the virgin gesso after a defined period of cycle occurrence - 100 years in this study. The allowable amplitudes were derived as a function of cycle duration, panel thickness and the configuration of moisture exchange by a panel with the environment. The worst-case duration of the RH cycles, for which the allowable amplitude is at its minimum, were calculated for varying thicknesses of the panels. The lowest allowable amplitude of fluctuations determined in this study was ±13% RH for a panel 30 mm thick and 0.5 mm thick gesso layer of composition and mechanical parameters commonly used in the restoration of panel paintings. The decrease in the gesso’s thickness reduces the restraint placed on the wood substrate by the gesso, and hence reduces the allowable amplitude of RH cycles.
Applied Optics, 2012
A fully automated algorithm was developed for the recording and analysis of vibrating objects wit... more A fully automated algorithm was developed for the recording and analysis of vibrating objects with the help of Digital Speckle Pattern Interferometry (DSPI) utilizing continuous wave laser light. A series of measurements was performed with increasing force inducing vibration to allow the spatial distribution of vibration amplitude to be reconstructed on the object’s surface. The developed algorithm uses Hilbert transformation for a an independent, quantitative evaluation of the Bessel function at every point of the investigated surface. The procedure does not require phase modulation, thus can be implemented within any, even the simplest, DSPI apparatus, and the proposed deformation analysis, is fast and computationally inexpensive.
Journal of Cultural Heritage, 2012
Digital Speckle Pattern Interferometry (DSPI) and Speckle Decorrelation (DIC) were used in condit... more Digital Speckle Pattern Interferometry (DSPI) and Speckle Decorrelation (DIC) were used in condition surveys of a wooden altarpiece in the church of Hedalen, Norway. Two surveys were conducted, one before and one after the heating season in the church to trace the possible development of damage in the paint layer caused by relative humidity variations induced by the heating system. The measurements demonstrated that the speckle techniques can contribute to detecting irregular areas on the paint surface and in the paint structure. They proved particularly effective in tracing paint detachments at an incipient stage which cannot be easily detected by an unaided eye or manual inspection. The results of the speckle techniques may thus guide a traditional conservation survey, or the use of further microscopic or analytical survey techniques. The speckle techniques could be routinely used by conservation practitioners who are not scientists if simple, portable instruments were available on the market.
Journal of Cultural Heritage, 2012
A broad category of cultural heritage objects are multi-layer structures composed of organic, hum... more A broad category of cultural heritage objects are multi-layer structures composed of organic, humidity-sensitive materialswood, animal glue, paper, leather, bone or paints. They respond to variations in relative humidity (RH) in their environment by cyclically gaining and losing moisture, and consequently swelling and shrinking. Differences in the moisture response of the materials induce internal stresses in the individual layers of the structures which cause objects to deform and crack. Polychrome wood is examined in detail. The cumulative physical damage of the design layer on wood due to repeated RH variations is quantified in terms of their magnitude and number of times they occur. The climatological risk index for accumulated, 'fatigue' damage is established, using a procedure to reduce irregular real-world climate histories into simple RH cycles of known damage impact. Using output from the Hadley Model (HadCM3) and simple transfer functions predicting indoor temperature and RH from outdoor climate, changes in the indoor climate through to 2100 were forecast for unheated buildings. European maps highlighting the areas in which painted wood may be significantly affected by climate change are presented.
Strain, 2012
Numerical modelling was used to follow the moisture movement and strain in a composite systeman u... more Numerical modelling was used to follow the moisture movement and strain in a composite systeman unrestrained, single wood panel coated with a layer of gesso, in response to cyclic sinusoidal variations in relative humidity (RH). The allowable magnitude of the variations, below which physical damage of the gesso layer on the wood does not occur over a selected time of exposure, was derived as a function of cycle duration, panel thickness and moisture diffusion configuration. The dimensional response of wood substrate becomes subject to restraint by the applied layer of gesso. The panels do not respond significantly to diurnal fluctuations or shorter irrespectively of the panel thickness. The panels respond more and more significantly when the duration of the fluctuations increases until a certain critical period at which the panel fully responds to each cycle. The analysis of the data obtained indicates that moderate RH variations within the approximate range 50 ± 15% are safe. This safe range was derived using the extremes of conservative criteria of the gesso's fatigue fracture and assumption of worst case wooden substrate response. The reduction of allowable amplitude of RH cycles due to decrease of the gesso's modulus of elasticity and thickness is discussed.
Strain, 2012
The finite element method was used to model the moisture movement and strain in the wood supports... more The finite element method was used to model the moisture movement and strain in the wood supports of panel paintings, in response to changing climate conditions – temperature and relative humidity (RH). The material properties of lime wood (Tilia sp.), determined experimentally, were used in the modelling. Critical amplitudes of cyclic sinusoidal RH fluctuations generating strain of 0.002 in the most responsive tangential direction of the unrestrained, single wood panel, which the pictorial layer was assumed to endure without damage, were derived for the mid-RH region as a function of cycle duration, panel thickness and diffusion configuration. Panels do not respond significantly to diurnal fluctuations or shorter. The panels respond more and more significantly when the duration of the fluctuations increases until the panel fully responds to each cycle. These fluctuation periods are 14 and 90 days at 20 _C for a panel thickness of 10 and 40 mm, respectively, with two faces of a panel diffusively opened. Sinusoidal RH variations bringing about wood’s full response have the critical amplitude of ±6% RH, that is strain of 0.002 endangering the pictorial layer is produced at such amplitude in the tangential direction of the unrestrained panel.
Optica Applicata, 2012
The aim of this work was to evaluate the applicability of optical fiber Bragg grating (FBG) senso... more The aim of this work was to evaluate the applicability of optical fiber Bragg grating (FBG) sensors to the monitoring of deformation in historical textiles and paintings on canvas. Fibers with a ceramic coating were selected for strain investigation in textiles due to both their almost perfect strain transfer and much shorter relaxation times compared to fibers with an acrylate coating. FBG sensors were attached to fabrics in a non-destructive manner using specially designed magnetic clamps. Local strain measurements using these sensors were consistent with general strains measured using either a universal testing machine (UTM) or a laser triangulator when varying external load or relative humidity. However, strain magnitudes measured by the different methods were comparable only after correction for the influence of the fiber on the textile under study. Strain measurements in model paintings on canvas were carried out using uncoated fibers embedded in the gesso layers on the canvas.
Despite some drawbacks, the FBG sensors were found to be useful in monitoring strain in historic textiles and consequently, for the assessment of environmental risk of these works-of-art.
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Papers by Michal Lukomski
Despite some drawbacks, the FBG sensors were found to be useful in monitoring strain in historic textiles and consequently, for the assessment of environmental risk of these works-of-art.
Despite some drawbacks, the FBG sensors were found to be useful in monitoring strain in historic textiles and consequently, for the assessment of environmental risk of these works-of-art.