Radiocarbon dating of canvas paintings: two case studies

Abstract

Well-cleaned canvas fibres from two oil paintings have been dated by radiocarbon. Although the dates agree with the expected ages of the paintings to a first approximation, uncertainties in the date arise from ambiguities (or ‘wiggles’) in the calibration curve. Only by introducing additional information about the paintings into the calculations can more precise results be obtained. Two paintings have been dated in this way, using the radiocarbon dating technique in conjunction with dendrochronological and art historical information.     

Prediction of the relative humidity response of backboard-protected canvas paintings

Abstract

simple mathematical model is presented that predicts the decay time of the internal relative humidity (RH) of backboard-protected canvas paintings when subjected to external RH fluctuations. The model takes into account the permeance of the canvas and the hygroscopicity of the enclosed materials. Predictions from the model are tested experimentally. The wooden stretcher releases moisture more slowly than expected, providing less buffering than predicted by the model. The practical implications of these findings are discussed.     

Distribution of moisture in reconstructed oil paintings on canvas during absorption and drying: A neutron radiography and NMR study

Moisture is a driving factor in the long-term mechanical deterioration of canvas paintings, as well as for a number of physico–chemical degradation processes. Since the 1990s a number of publications have addressed the equilibrium hygroscopic uptake and the hygro-mechanical deformation of linen canvas, oil paint, animal glue, and ground paint. In order to visualise and quantify the dynamic behaviour of these materials combined in a painting mock-up or reconstruction, we have performed custom-designed experiments with neutron radiography and nuclear magnetic resonance (NMR) imaging. This paper reports how both techniques were used to obtain spatially and temporally resolved information on moisture content, during alternate exposure to high and low relative humidity, or in contact with liquids of varying water activities. We observed how the canvas, which is the dominant component in terms of volumetric moisture uptake, absorbs and dries rapidly, and, due to its low vapour resistance, allows for vapour transfer towards the ground layer. Moisture desorption was generally found to be faster than absorption. The presence of sizing glue leads to a local increase of moisture content. It was observed that lining a painting with an extra canvas results in a damping effect: i.e. absorption and drying are significantly slowed down. The results obtained by NMR are complementary to neutron radiography in that they allow accurate monitoring of water ingress in contact with a liquid reservoir. Quantitative results are in good agreement with adsorption isotherms. The findings can be used for risk analysis of paintings exposed to changing micro-climates or subjected to conservation treatments using water. Future studies addressing moisture-driven deformation of paintings can make use of the proposed experimental techniques.     

The Age- Embrittlement of Silver Coins

Abstract

Conservation treatments of three modern paintings are presented which illustrate the use of Beva 371 in solving difficult and varied conservation problems. They were selected as representing cases which could not have been solved satisfactorily with other adhesives and are: 1. Gottlieb, oil on glue-sized cotton. Transparently lined with Mylar; 2. Balthus, casein on unprimed canvas. Mounted on a solid support; 3. Klee, gouache on decaying, unprimed burlap. Transparently lined on silk chiffon.     

Public AI canvas for AI-enabled public value: A design science approach

Public agencies have a strong interest in artificial intelligence (AI) systems. However, many public agencies lack tools and frameworks to articulate a viable business model and evaluate public value as they consider investing in AI systems. The business model canvas used extensively in the private sector offers us a foundation for designing a public AI canvas (PAIC). Employing a design science approach, this study reports on the design and evaluation of PAIC. The PAIC comprises three distinctive layers: (1) the public value-oriented AI-enablement layer; (2) the public value logic layer; and (3) the public value-oriented social guidance layer. PAIC offers guidance on innovating the business models of public agencies to create and capture AI-enabled value. For practitioners, PAIC presents a validated tool to guide AI deployment in public agencies.     

Conservation of a Chinese gu at the Canadian Conservation Institute

Abstract

Conservation and technical issues pertaining to the investigation of six mediaeval Spanish ceramic lustre fragments are reported. Assessment of methods and materials to replicate the lustre glazes indicates that the spray application of nacreous (pearlescent) pigments in combination with conventional inorganic pigments and transparent colorants in an acrylic lacquer gives good results. The salient optical features oflustre glazes and nacreous pigments are discussed. Scanning electron microscopy in conjunction with electron diffraction studies are employed to characterize the glaze and ceramic body composition of the fragments. Transmission electron microscopy indicates that a uniform dispersion of copper crystallites, c. 2-4nm in diameter, is responsible for the lustre effect in one sherd.     

A structural solution for the preservation of canvas paintings

Abstract

Information obtained from 18 surviving panoramas and cycloramas, and a study of the behavior ofcanvas paintings on conventional stretchers under changing environmental conditions, have led the author to develop a new self-adjusting continuous-tension stretcher, which is described in detail.     

COLOURMEN’S CANVAS STAMPS AS AN AID TO DATING PAINTINGS: A CLASSIFICATION OF WINSOR AND NEWTON CANVAS STAMPS FROM 1839–1920

Abstract

The role of colourmen’s canvas stamps in dating paintings is discussed. A series of 16 Winsor and Newton canvas stamps is illustrated in conjunction with a dating table, the resulting system being of practical use for dating paintings bearing Winsor and Newton canvas stamps.     

The Effect of Changes in Environmental Conditions on the Mechanical Behaviour of Selected Paint Systems

ABSTRACT

The impact of relative humidity (RH) and temperature variation on the mechanical behaviour of paintings on canvas was investigated, based on the various environmental recommendations that are applied by museums and institutions worldwide. Paint samples were constructed based on the works of twentieth-century artists such as Soulages and Riopelle. The various samples are based on criteria such as paint media, additives, pigment type, canvas type, thickness, type of application, and drying time. Once they are fully dry, paint films behave as elastic, viscoelastic, or viscoplastic materials depending on the chemical nature of their components. These properties, as well as tensile strength, were determined by a series of tensile tests. Other samples were included, originating from discarded oil paintings on canvas from the seventeenth and nineteenth centuries. To carry out mechanical tests under controlled conditions of temperature and RH, a climatic chamber was built around the column of a universal testing machine. Samples were submitted to stress relaxation tests to observe their response to changes in environmental conditions. RH was increased from 20 to 90% and temperature from 15 to 60°C. Reactivity diagrams were drawn based on the results. The endurance limit under mechanical fatigue was determined from the diagrams and helped define the risks associated with each painting type when exposed to the accepted environmental recommendations.     

A New Hot Table for Relining

Abstract

Two red dyes from 21st dynasty Egypt and one from the 12th dynasty were analyzed. The first two were essentially madder, in one case mixed with small amounts of tannins. The third contained pure haematite (red ochre), thus representing one of the earliest known uses of this pigment for the dyeing of linen.     

NOTES ON THE USE OF A VACUUM HOT-TABLE FOR TEXTILES

Abstract

A miniature low-pressure apparatus for localized treatment of paintings is described. Alternative working surfaces are available which allow heat and moisture treatment on canvas paintings without removal from their stretchers. Other applications of the apparatus are discussed.     

THE DISCOVERY AND CONSERVATION OF AN ANCIENT EGYPTIAN LINEN TUNIC

Abstract

The archaeological evidence for dating a linen tunic found amongst other pieces from the Petrie Museum of Egyptian Archaeology, UCL, is weighed against the evidence from Carbon-14 dating. An account of the structure, conservation and mounting of the tunic is then given.     

VERDIGRIS AND COPPER RESINATE

Abstract

A history of the Patent Stretcher Key invented by Aaron Draper Shattuck (1832-1928) is described. The technical use of keys in stretchers for canvas paintings is illustrated. Developments prior to Shattuck’s patent of 1883 are reviewed and later infringements are discussed. A survey is given of the production, merchandising and obsolescence of the Shattuck keys.     

Making Space for Storytime: The Role of the Environment in the Production of Storytime

ABSTRACT

This article reviews the findings from Project VIEWS2, a four-year IMLS-funded study that examined the early literacy impact of public library storytimes, and provides detail on a secondary analysis of storytime spaces that was done using the Project VIEWS2 dataset. The storytimes spaces were explored by looking at the spatial quality, physical literacy environment, and seating of attendees, as these characteristics have been identified as important aspects of early childhood learning environments. Findings across these three characteristics are presented as well as implications and recommendations for more effective storytime practice and space design.     

Lighting the Shroud of Turin for Exhibition in 2015

ABSTRACT

Lighting a cultural heritage artifact requires balancing visual perception with preventive conservation, by providing the best lighting (in terms of spectral distribution and quantity) to enable the viewer to appreciate details and color, while limiting photo-induced degradation. The paper outlines the methodology applied by a multi-disciplinary team while lighting the Shroud of Turin at its last public exhibition in 2015. The methodology considered the special requirements of the Shroud, including exposure to ultraviolet light, while providing appropriate display conditions that would meet audience expectations. The desired appearance (readability of the body image and color) was defined with the help of Shroud researchers and confirmed by subjective tests, while appropriate light levels for preservation were set in agreement with standard requirements and using knowledge of the degradation of linen in visible and UV light. The installation provided a controlled environment and a managed visitor route to the Shroud, assuring excellent perception of both details and color, with the lowest illuminance level about 15?lx.     

Ethyl Silicate for Unbaked Earth Tablets Conservation: Evaluation of the Physico-mechanical Aspects

ABSTRACT

Preservation of cuneiform tablets made with clay minerals is an ongoing conservation issue. A treatment based on TEOS consolidation has been used since 1996 at the Louvre museum. The characterization of the tablets pointed out kaolinite, illite, and smectite as the three main clay minerals constituting the objects. In this research, the physico-mechanical aspects of the treatment are investigated. The penetration depth of the TEOS solution and the gradient induced are quantified using laboratory samples. TEOS treatment preserves the macroscopic swelling and the vapour transfer properties, but modifies the clay’s affinity to moisture. Elastic properties are gradually improved for all clays, but only kaolinite’s strength increases significantly. The impact of TEOS treatment on the natural behaviour related to the respective structure of the clays is considered, and the amount of kaolinite required to create adequate reactions appears to be of interest for conservation treatments.     

A review of conservation treatments of waterlogged basketry from the northwest coast of North America

Abstract

Basketry artifacts fabricated from spruce and cedar limb wood and root and the inner bark of yellow and western red cedar have been found in water-saturated archaeological sites in the Pacific Northwest since the mid-twentieth century. These artifacts range in age from a few centuries to more than 5000 years old. While these materials retain their overall physical structure due to burial in an anoxic environment they are degraded on the cellular level. Experiments and treatments performed by archaeologists and conservators over the past 50 years have attempted to stabilize these degraded structures and minimize splitting, crumbing, and distortion of the woven structures as they dried. Many of these tests and treatments are published in out-of-print conference proceedings or remain unpublished in conservation lab records. This review of tests and treatments as well as a current condition assessment of several collections brings this information together for the first time and allows conservators and archaeologists specializing in these treatments to see the broader arch of success and failure of the preservation of waterlogged basketry materials.     

The presence of antimony in some grey colours of three paintings by Correggio

Abstract

This paper describes analyses that were performed on three canvas paintings by Correggio, the‘Danae’, the‘Compianto suI Cristo Morto’ and the‘Martirio di Quattro Santi’, with special regard to the grey colours. Non-destructive XRF measurements showed that the elemental composition of these colours included non-negligible amounts of antimony, and that its abundance was related to the darkness of the colour. Optical microscope, SEM and EPMA analyses, carried out on a single sample taken from the‘Danae’, confirmed that antimony was associated with the grey layers of the stratigraphical section and allowed us to hypothesize the presence of stibnite, which is a lead-grey coloured antimony trisulphide.     

Fabrication of an Ultrasonic Nebulizer: Rate of Flow and Performance Studies

ABSTRACT

This article describes how to build, in-house, a new type of ultrasonic nebulizer and presents the results of tests to determine its rate of aqueous flow and its performance during the transport of a collagen-based adhesive (ratio of adhesive actually delivered to adhesive misted). It also reports on a consolidation treatment case study carried out with the new ultrasonic misting prototype: the NebulA-MG 14. This case study was applied to powdery paint layers of a medium-sized oil painting on canvas, 111.5?×?86.5?cm. The new device is shown to be both reliable and effective, particularly for consolidating medium and large-sized works.