Search

českyčesky | englishenglish

Pre-restoration materials research

Subjects of pre-restoration materials research in ALMA are easel paintings, polychrome sculptures and wall paintings.

Materials research on art work is a traditional part of its restoration or artistic evaluation. Contrarily to the study of artistic aspects of the art work, materials research is based on objective identification of materials and painting techniques from materials microsamples. The success of that identification depends on the nature of the studied objects and samples and a proper choice of analytical methods.

A current problem in the Czech Republicis that the materials examination is aimed insufficiently, engaged and carried out improperly, without previous discussion with materials scientists. The quality of investigations also varies a lot – mere instrumental measurements are presented as expertises and interpretations are carried out without sufficiently complex and deep knowledge of the subject. Contrarily to this approach, the artwork examination in the ALMA Laboratory is based on knowledge built systematically by a long-term research in the field of conservation science which bears international comparisons and can be proved by many publications abroad (see References – Publications). An examination aimed at particular subject is not a mere data collection but is effective and as a result also more friendly to an artwork.

Materials research in ALMA can be divided into:

  • non-invasive examination (without the necessity of taking a sample) -  carried out in situ by portable instruments)
  • laboratory examination-carried out in a laboratory on taken microsamples

 

Materials examination in ALMA usually includes:

  • elemental composition screening covering the whole area of the painting using portable X-ray fluorescence method which enables a preliminary identification of most inorganic pigments and determination of secondary treatment (it is useful to combine with non-destructive optical investigation methods and probing)
  • description of the stratigraphy of colour layers to distinguish original layers, re-paints, secondary changes, artistic post-treatment, and defects
  • identification of pigments in colour layers and their further specification related to the dating and provenancing of the artwork
  • identification of binders of colour layers and description of the painting technique
  • description of microstructure of colour layer representing a technical pattern of the author
  • support’s materials identification (wood, canvas, etc.)

The fundamental methods of the materials research of microsamples are optical and electron microscopies.

The sufficient number and representative choice of samples taken from art works are a indispensable pre-requisites of the stratigraphic analysis. On the other hand, the sample size is not critical. Smaller but properly chosen sample of the painting layer is better than a large sample from edges or defects. Taking non-representative samples is a useless intervention to the art work, because their examination will not answer the most frequent questions. The team fully respects the responsibility of the restorer to works of art and intensely pays attention to optimization of analysis to apply most of analytical techniques to a single sample polished in the cross-section prepared for microscopy.

Interpretation of the colour-layer stratigraphy in materials examination is based on observation in Vis and UV light using light microscope and from chemical contrast in electron microscopy (SEM). Each of these three kinds of imaging is important to follow further features, such as colour, luminescence, and chemical composition. Invaluable feature of electron microscopy is its better spatial resolution (magnification) permitting to study morphological details and inner structure of layers and distinguish fragmentary lines and tiny technical interventions invisible in optical microscope. Detailed analysis of elemental composition and heterogeneities is a common part of the analysis by electron microscope (SEM/EDS). Our group utilizes an electron microscope permitting a work in the low vacuum. Consequently the analysis does not require the metallization of the specimen as some other electron microscopes. Hence, the analysis is not destructive to the taken sample