Analysis and documentation

At C.R.A. Conservación y Restauración de Arte each work is subjected to detailed photographic documentation of the initial state, the restoration process and the final state. We use special photographic techniques such as macro and microphotography, raking light, transmitted light, and ultraviolet fluorescence photography. We also make computerised graphic images of all the data relating to the construction technique, state of conservation, any possible prior interventions and the treatments carried out. In cases when more knowledge is required about the materials used in the work, C.R.A. provides various scientific research methods suitable for works of art, such as chemical and stratigraphic analyses of paint layers, which are done in collaboration with Larco Química y Arte, S.L., a firm that specialises in diagnosing and researching artworks. X-ray examination is an essential non-invasive technique that makes it easier to recognise the internal structures of artworks, providing valuable information. When deemed necessary, this procedure can be done by specialised technicians.


Each work of art that arrives at the C.R.A. Conservación y Restauración de Arte workshop is subjected to detailed photographic documentation, using visible light, of the initial state, all the phases of the restoration process and the final state.

  • Macro and microphotography. To document key technical data about the paint layer, alterations or signatures, identifying marks, etc., we take digital macro and microphotographs using macro lenses or a camera mounted on a binocular microscope.
  • Raking light photography. This technique makes it possible to obtain valuable information about the construction technique used and the conservation state of the artwork. Raking light photography is done by illuminating the object from one side, with the source of light at an angle of incidence that is always greater than 80°. In this way, the three-dimensional aspect of the object’s surface comes into view as a consequence of the shadowed areas that are created, often making it possible to obtain pertinent information.
  • Transmitted light photography. With this technique, the source of light – in this case visible light – is placed behind the painting, making it possible to photograph the transparency of the object’s materials. This technique can only be used when the support allows partial transparency to visible light, as is the case with some canvas paintings with non-laminated supports. The image obtained provides important data about the support’s state of conservation, revealing cracks, losses, tears in the fabric and information about the thickness of the preparation and paint strata.
  • Ultraviolet fluorescence photography. Of all the diagnostic methods in the field of historico-artistic property, ultraviolet fluorescence examination is particularly useful when identifying prior interventions, such as retouching and superimposed varnish layers. Observation using ultraviolet fluorescence can differentiate or reveal the presence of materials that are not easily distinguished with visible light, making it possible at times to identify different substances or revealing specific accumulation.


Creating and mapping graphic images of artworks can be extremely useful as a way to capture all the information gathered by technicians from field notes, photographs, chemical analyses, ultraviolet illumination, X-ray studies, and so forth. These records are collected before, during and after the restoration work, and data are compiled on the construction technique, the state of conservation, possible prior interventions and any restoration treatment done on the work. Later, these data are computerised and graphed.


Chemical analyses and stratigraphic studies of paint or polychrome layers provide another indispensible research tool in the field of art restoration and conservation. These analyses can be done to learn more about the material composition of the paint layer, to verify any possible superimposition of the paint strata, repainting or repolychroming, to make comparative studies with other analysed works and to learn more about the artwork before beginning the restoration. These studies are carried out in collaboration with Larco Química y Arte, S.L., a firm that specialises in diagnosing and researching artworks. The valuable scientific data that emerge from these studies is later interpreted by C.R.A. Conservación y Restauración de Arte.

These studies use different analytical techniques:

  • Reflected and transmitted light optical microscopy using polarised light. This is a basic technique that makes it possible to study the superimposition of paint layers, as well as make a preliminary analysis of pigments, binding media and varnishes, using selective colouration and microchemical tests of the hardening and oil layers. The microphotographs are taken with reflected light at 300X with crossed nicols.
  • Fourier transform infrared spectroscopy. This technique is primarily used in the analysis of varnish and coating components and preparations. These analyses, when necessary, are done between 4400 cm-1 and 370 cm-1 in KBr discs or with a surface analysis using the Universal Attenuated Total Reflectance (UATR) technique.
  • Scanning electronic microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). These techniques are used for the elemental analysis of pigment particles in order to determine their exact nature.
  • Gas-phase chromatography. This method is used for the determination of lipophilic substances such as drying oils, resins and waxes and of hydrophilic substances such as proteins and polysaccharide gums (gum arabic and similar products). For the analysis of lipophilic substances, samples are treated with Meth-Prep II, a methylation reagent. Carbohydrates and proteins are subjected to hydrolysis with 6M HCl, and the resulting fatty acids, amino acids and monosaccharides undergo derivatisation with MTBSTFA in pyridine.


    X-ray examination is an essential non-invasive technique that makes it easier to recognise the internal structures of works of art, providing valuable information. With X-rays, the techniques and systems used to construct the wood or canvas supports can be viewed. They also provide information about the painting material and are a useful tool when distinguishing materials, revealing where layers may be superimposed and any repainting or repolychroming. X-rays can be done on request with both paintings and sculptures when specialised technicians deem them useful or necessary.