Paintings and polychrome sculptures are made from many different materials (organic or inorganic, natural or synthetic) that interact with each other as well as with the microclimatic condition in their vicinity.
Any artifact is susceptible to deterioration. In fact, any material is affected by temperature, humidity, pollutants, microorganisms.
It is vital to understand the deterioration and degradation process occurring on heritage materials.
There are many analytical techniques that can be applied to art works. They provide more information useful to characterise a material (elemental composition, molecular structure and physical properties). The results of these analyses enable the conservator to better understand artistic techniques, materials used by the artist, previous intervention, deterioration factors. Analytical techniques are also useful for dating materials and detecting forgeries.
There are important considerations to be made when choosing suitable technique for studying an artifact. As the main aim is to minimise any damage or change to the art-work the non-destructive and non-invasive diagnostics are much more preferable. The imaging techniques fall into this non-destructive and non-invasive categories.
Claudia offers the following non-destructive and non-invasive diagnostic techniques that are recorded with standard and macro-photographic techniques using different radiation spectrums.
DIRECT, DIFFUSE, RAKING and TRANSMITTED light photography using the visible spectrum (VIS) (400-750 nm)
Direct and diffused light reveal losses of the painting layers, losses of the preparation layers, discolorations, previous interventions.
Raking light (the light source is placed to one side at a low angle of maximum 10º with the surface of the artifact under examination) reveals cracks, losses of painting and preparation layers, paint flaking, texture of the surface (e.g. thick brush strokes), artistic technique details (e.g. on a fresco it easily reveals ‘giornate’, direct and indirect incisions etc.) and enhance carved details, graffiti and lettering.
Transmitted light is a technique where the light source and the camera are in opposite sides of the artwork. The light source is usually placed on the back of the artwork while the the camera records the result on the front side. This technique is useful for examining paintings on canvas, paintings, drawings, illuminated manuscripts and manuscripts on paper or parchment, stained glass and reversed paint on glass. It reveals fissures, holes, cracks, differences in thickness.
Photo credit: Claudia Fiocchetti
INFRARED REFLECTOGRAPHY (IRR) using the near IR radiation (NIR: 750-3000nm)
The infrared examination technique enables to examine the ground layers of paintings, revealing what lies beneath the painting layers. With this technique is possible to detect under-drawings and out-lines, drawn by the artist on the preparation layers. It can also reveal signature and earlier alteration to a painting composition (e.g. ‘pentimenti’). The result obtained with this technique depends on the thickness and composition of the painting layers.
VIS-IRR image analyses of an oil painting on wood panel attributed to Joachim Beuckelear and dated 1568
Image analyses were undertaken on an oil painting (attributed to Joachim Beuckelear) for Robert and James Mulraine (www.jamesmulraine.com) in order to record the artist’s signature that was already spotted under UV light during the restoration treatment.
The results of this campaign reveal quite clearly the signature and the under-drawings and out-lines, drawn by the artist on the preparation layers.
To know more about the discovery of this paintings follow these links:
Joachim Beuckelaer’s ‘Fish Market’ – a new version rediscovered?
In the restorer’s studio: Beuckelaer’s ‘Fish Market’
Photo credit: Claudia Fiocchetti
FALSE COLOUR INFRA-RED PHOTOGRAPHY (FCIR)
It is an image analysis that combines visible and infrared imaging techniques. It is a colour rendering method used to display images in colours that are recorded in visible and infrared imaging techniques. An infrared false-colour image is an image that depicts an object in colours that differ from those shown by a true colour photograph. This technique accentuates differences of materials used. It reveals mostly retouching and over-paintings that in visible light appear to be the same colour of the original painting layers.
VIS-IRR-FCIR image analyses of Louis Cheron’s First State Room ceiling painting (c. 1695) at Boughton House – Kettering (Northamptonshire)
The image analysis diagnostic campaign was undertaken during The Perry-Lithgow partnership’s conservation project of the First State Room Ceiling Painting at Boughton House – Kettering (Northamptonshire).
The results of the IRR and FCIR imaging has revealed and confirmed quite clearly earlier alterations (known also as ‘pentimenti’), old retouching/repaint and paint layers abrasions.
Photo credit: Claudia Fiocchetti
ULTRAVIOLET FLUORESCENCE photography (UVF) and REFLECTED ULTRAVIOLET PHOTOGRAPHY (UVR) using the UV radiation (in the examination of artworks the UV band mostly used is the near UV of 360 nm)
The reflected UV and the UV fluorescence are two techniques that complement each other and give information about the surface of the painting layers (as well as print, drawing, water colours). They can reveal the presence of natural resin varnishes, but not recent varnishes. It is possible to identify retouching as well as over-paintings, which, in fact, are not fluorescent and appear dark/black. They are useful for assessing the condition of the varnish layer, detecting fungal growth, confirming the authenticity of signatures or inscriptions and checking the paining surface during cleaning process while varnish layers are removed. The UV radiation techniques have some limits and old intervention can’t be revealed as the materials used will become fluorescent after 80-100 years. The varnish layers of a painting can produce a very strong fluorescence making difficult to identify pigments. For this reason the UV radiation can be really useful to identify pigments in wall paintings.
VIS-IRR-UVF image analyses of the apse wall paintings at Holy Trinity Church-Guildford (Surrey)
Image analysis diagnostic campaign undertaken during Tobit Curteis Associates wall painting conservation project at Holy Trinity Church in Guildford (Surrey).
The infrared rays have the capability to pass through the varnish layer helping the conservation team to examine more clearly the painting layer, which is recorded with the IRR technique. The UVF reveals the areas where varnish coat was applied in past intervention (blue areas) and where it was applied shellac (gilded areas that appear in orange-brown tone). As the UVF enhances also the varnish drippings it can be assessed that the shellac was applied before the varnish, but both coats seem being applied during the same past intervention.
Photo credit: Claudia Fiocchetti
Being the equipment portable Claudia is able to perform these image analysis diagnostic campaigns on site and in situ.
Claudia Fiocchetti 