CHSOS serves an international audience of art professionals: conservators, art historians, and conservation scientists. Its technical innovations and strategies are being adopted by museums and cultural institutions worldwide. CHSOS disseminates this knowledge through the CHSOS website, publications, and training programs.
- Our Training programs teach practical methods for Art Examination and Documentation. Our modules illustrate imaging and spectroscopy methods regularly used by cultural heritage scientists and conservators for the scientific and forensic investigation of art objects.
- All the training modules have hands-on activities and students practice with our CHSOS equipment. No needs for you to bring any equipment.
- Our audience is made of art and archaeology professionals: conservators, conservation scientists, art appraisers and fine art photography.
- No specific educational background is necessary. Our courses are designed for a large audience ranging from art professionals to scientists.
We offer instruction on these methods: Technical Photography (TP), Panoramic Infrared Reflectography (PIRR), Reflectance Spectroscopy (RS), Reflectance Transformation Imaging (RTI) and Multispectral Imaging (MSI).
A standard 3-days (6 hours per day) training program presents all the methods:
- 1st day. Technical Photography
- 2nd day. Infrared Reflectography, Reflectance spectroscopy, RTI
- 3rd day. Multispectral Imaging
Read a brief introduction to these methods.
Technical Photography (TP) represents a collection of images realized with a modified digital camera sensitive to the spectral range about 360-1000 nm.. Different lighting sources and filters are used to acquire a selection of technical images, each one providing different information regarding the object under examination.
A Technical Photography documentation consists of a collection of scientific images realized with a modified digital camera sensitive to the spectral range about 360-1000 nm. Each image provides just a bit of information but all together they represent the most practical and successful methodology to study art and archaeology.
Art examination starts with a high-quality photographic documentation in the standard visible range of the electromagnetic spectrum. Color camera calibration, exposure correction, white balance, sharpness. color checkers, resolution. These are some of the topics to master in order to obtain quality photo documentation of art objects and archaeology. Polarized light photography (PL) and Raking light photography (RAK) are very helpful photographic methods widely used by fine arts photographers and they also belong to the visible range of the spectrum.
Raking light photography (RAK) is a very simple method. Nevertheless, it allows to reveal and to document numerous information. A standard VIS photo is intended to reproduce the look of the artwork as seen in museum lighting, with soft and diffused light. RAK photo clearly shows how the paint was laid (brushwork), texture and building up of figures and details.
Ultraviolet Fluorescence photography (UVF)
Some Art and conservation materials (pigments, binders, varnishes, consolidants, adhesive…) exhibit the emission of visible light of different colors when they are exposed to ultraviolet radiation. This phenomenon – called ultraviolet fluorescence – can be appropriately documented using proper filters and UV lamps and it provides plenty of information on the presence and distribution of these materials. Among the technical photographic methods, UVF is the most widely used for many kinds of artifacts; paintings, textiles, paper, historical documents, stone, even photography conservation.
Ultraviolet Fluorescence photography (UVF) is probably the most diffused technical method for art examination since it can be successfully applied on practically every art or archaeology object category. In a painting, UVF photo reveals retouchings as dark spots while the aged original materials exhibit light emission with different colors.
Reflected Ultraviolet photography (UVR)
The main application of this methods is to identify and map modern white pigments (zinc white and titanium white) which absorb UV radiation and appear dark in UVR photography. On the other hand, the historical lead white pigment is a very good UV reflector and shows up very bright in UVR images. Lead white was used from antiquity to the 1920′ when the modern and safe titanium white totally replaced it. UVR photography is a very effective method to tell the presence of inpaints made with modern white over original lead white.
The main application of this methods is to identify and map modern white pigments (zinc white and titanium white) which absorb UV radiation and appear dark in UVR photography. On the other hand, the historical lead white pigment is a very good UV reflector and shows up very bright in UVR images.
Infrared photography (IR)
Some pigments become transparent in the near infrared and infrared photography can reveal underdrawing and changes. in particular ochre pigments (yellow ochre, red ochre, raw sienna…) and red and yellow lakes are the ones that become more transparent totally revealing traces of hidden drawing.
Infrared photography can reveal underdrawing, changes and even faded signs, as in this example. Some pigments become transparent already in the near infrared range that a modified digital camera can detect. The dark pigments in this example disappear in the IR image revealing the white support and the sign which was written with a carbon-containing paint which remains opaque in IR.
Infrared False Color photography (IRFC)
Infrared False Color photography (IRFC) is used to map inpaints and to tentatively identify pigments or at least distinguish original paints from inpaints. Even if the original pigments and the modern ones used for the conservation treatment have the same visible color and cannot be distinguished by the naked eye, IRFC photography can reveal the new paints if they reflect or absorb infrared differently than the original ones.
Infrared False Color photography (IRFC) reveals inpaints making easy to distinguish original paints from later additions. Original pigments and the modern ones used for the conservation treatment have the same color and cannot be distinguished by naked eye. On the other hand, the original paint absorbs infrared while the modern one reflects it, thus the different infrared false colors.
Some molecules and minerals (among them mineral pigments) exhibit Infrared Fluorescence. This phenomenon is similar to Ultraviolet Fluorescence where a beam of ultraviolet light produces visible light emission. In the case of infrared fluorescence, a beam of visible light generates an emission of infrared radiation. IRF photography allows to map and detect Egyptian blue and cadmium-based pigments.
Infrared Fluorescence photography (IRF) makes retouches with cadmium-based pigments to stand out as bright spots. In this example, the vermilion used for the red drapery of this oil painting was retouched with modern cadmium red which appears bright in the IRF image.
Transmitted Infrared photography (IRT) allows to detect underdrawing and pentimenti. It is a very effective since pigments become even more transparent than in the usual IR photography method. IRT can be applied only for art objects on translucent supports, such as paintings on canvas, drawings on paper, historical documents and manuscripts.
Transmitted Infrared photography (IRT) could results even more successful than standard IR photography in revealing the underdrawing and the building up of the figures. This example shows how the exact sequence how the paint layers were laid on. Notice the red drapery was added on a naked right arm already sketched.
Panoramic Infrared Reflectography (PIRR) is a valid alternative to the much more expensive scanners for Infrared Reflectography (IRR) which is the imaging of works of art with a scientific camera in the range 1000- 1700 nm or further. Pigments such as azurite, Prussian blue and malachite become transparent only in the far infrared at about 1500 nm. The PIRR method consists of taking a series of images of a scene with a precision rotating head and then using panoramic software to align and stitch the shots into a single, seamless panorama. It can be implemented with consumer panoramic imaging tools, which can be upgraded following technical developments; as opposed to infrared scanners, which are products that cannot be modified. Self-assembled, modular equipment can be modified for specific tasks and upgraded with a comparatively little budget, following technical and scientific developments in the consumer market, e.g. upgrading to an InGaAs camera with higher pixel count. The stitching software is easy to use; the overall panoramic method does not require specialized personnel or intensive training and, for these reasons the method is appealing to medium‐small museums and private conservators who want to implement an affordable method to professionally document their objects.
Infrared Reflectography (IRR) makes pigments more transparent than IR photography. Though, IRR cameras have much smaller sensors so it is necessary to acquire a large number of images with the panoramic head and then stitch them together using the Panoramic stitching software.
In the analysis of polychrome artworks, among the techniques available in the portable version, Reflectance Spectroscopy (RS) has been established as a powerful one for the identification of pigments. An RS spectrum shows for each wavelength, the ratio between the intensity of the reflected light and the incident light, measured with respect to a standard white reference. This ratio is called reflectance and is given in percentage (%). The RS spectra can provide information useful for pigments identification since the radiation that is not reflected is absorbed or transmitted depending on the chemical composition of the material tested. The peculiar advantage of this method with respect to the other spectroscopies most commonly used, such as XRF and Raman, is that the RS equipment can be assembled with relatively low-cost components.
Multispectral Imaging (MSI) is used to identify and map pigments in polychrome artworks and to enhance the reading of faded historical documents. Conservators can use this technique to distinguish original sections from inpaints and to select the proper conservation procedures. MSI analysis is based on the same concepts of Reflectance Spectroscopy but MSI has the added advantage that the pigments can be identified and mapped remotely on large areas rather than just a spot. Images of an object in a series of spectral bands are acquired, and once the images are registered and calibrated, they are uploaded into a Reflectance Image Cube. We developed and we propose an affordable MSI system with a complete workflow for spectral images calibration, registration, and pigments mapping.
Reflectance Transformation Imaging (RTI) is a computational photographic technique used in a number of fields related to art examination and documentation. RTI provides a virtual and enhanced visualization of an object’s surface where the lighting direction can be changed interactively and enhancements can be performed to make surface’ details more visible. It relies on the Polynomial Texture Map method which is an image-based representation of the object’s surface achieved by capturing the object under lighting from different directions. It is used to visualize tiny incisions in paintings and historical prints as well as to document highly reflective objects such as coins.
Reflectance Transformation Imaging (RTI) is used to document tiny features, such as incisions in paintings and historical prints techniques. RTI is used in a number of fields related to art and archaeology examination because it provides a virtual and enhanced visualization of an object’s surface. This is an example of RTI documentation of historical graffiti in catacombs.
How to participate
We organize training programs in our studio in Italy Check out the calendar. You can invite us to deliver a training program in your location and in your Institution. Click HERE for more info. We have been serving a large community of worldwide institutes (click to see the list).
Are you interested in taking our training and also purchasing our equipment? Ask for our Train&Go program. We install and test the equipment in your place and train you how to use it, so you are ready to go. Ask for our special discounted fee for Train&Go programs (click to see the list of institutes that took the Train&Go program).
Instructor’s short bio
The Training program will be run by Dr Antonino Cosentino. CHSOS’s director. Dr. Antonino Cosentino is a Ph.D. physicist specialized in Art diagnostics who has taught
“Scientific Methods for Art Investigation” in Europe and US. He is an expert in imaging and analytical techniques which he has carried out on important works of art for European and American Institutions and private collectors. For more information on his scientific work visit Dr. Cosentino on Researchgate, Linkedin, and Academia.edu or check out our publications.