Laboratory analysis
aim at determining the initial technique that was used for the specific work of art and possible repaints that followed later which is obtained through stratigraphic studies of cross-sections, identification of the pigments and binding agents. Such study helps to date and authenticate the work of art.
The most important part of the research process is forming a question that is to be answered by the researcher. Such information helps to select correct analytical techniques. Usually, it is necessary to use several methods that, combined, help to obtain a reliable result.
The pricing process of a given analysis starts with determining the customer’s needs. In order to prepare an offer, we kindly request you to fill in the form.
Zamojski Academy. Paint layers section.
STRATIGRAPHIC STUDY OF THE PAINT LAYERS
is the basic analysis that helps to understand the original painting technique and follow the history of an object by analysing the sequence of layers.
In order to perform stratigraphic analysis, we need a small fragment of a painting (minimum sample size – 0.2 mm; recommended – 2 mm.) The size and the quality of the sample influences directly the quality of the analysis. Sample preparation is selected basing on the type of material and the further research planned.
Under the original yellow paint layer a metal leaf can be observed. The painting was made on the foundation covered with imitation gold leaf.
Observation of the sample cross-sections are conducted under optical and scanning electron microscopes at various magnifications.
Standard magnification applied for sample examination with reflected light microscope ranges between 100 and 400 times. It allows us to watch coarse grain pigments, such as malachite or azurite (average size varies between 10 and 40 μm).
The sample shows a mixture of sharp-edged azurite and spherical malachite.
PIGMENT IDENTIFICATION
is used as a basis for the procedure of paint layers dating. Pigments are identified through the basic techniques, i.e. optical microscopy, characteristic reactions and electron microscopy including EDS detector. Sometimes, it is necessary to reach for a more advanced technique: infrared spectroscopy, Raman spectroscopy, X-ray diffraction, electron microscopy involving WDS detector.
Synthetic ultramarine under transmitted light.
Natural ultramarine under transmitted light.
Pigment observation under transmitted light optical microscope
This type of analysis requires a powdered sample. Pigment is viewed with transmitted and polarised light microscope which enables a maximum magnification of 1000 times allowing viewing the pigments with minimum grain size down to 0.5 μm, such as white lead.
Red lead in transmitted light.
Characteristic interference colour emitted by read lead particles in transmitted polarised light.
Sample analysis under SEM microscope with EDS detector
Pigments with grain size smaller than 0.5 μm (e.g. titanium white, cadmium red) may be observed under scanning electron microscopes only, as they offer the magnification of several hundred thousand times.
Electron microscopes coupled with detectors (EDS, WDS) make it possible to receive additional information concerning elemental composition of the viewed grain.
Cross-section of WB4 sample. Photographed in reflected light. 5 technological layers have been detected in one chronological phase.
Image of a fragment of a sample in back scattered electrons with the EDS spectrum showing the elemental composition of a spherical grain.
Analysing the EDS spectra.
BINDING MEDIA ANALYSIS
helps us to expand our knowledge about an object, explain what caused the damage and select the correct conservation materials. Binding media are determined through the chemical methods, characteristic reactions and specific staining tests. We also collaborate with research centres that perform studies using spectroscopic, chromatographic and proteomic methods.
Cross-section of WB19 sample before the staining tests.
Ponceau S.
FTIR spectra of a standard sample of wax and a sample of lining adhesive from Jan Matejko’s painting „Reytan, or the Fall of Poland”.
Sudan Black B.
Lugol’s solution.
PLASTER ANALYSIS
offers an opportunity to follow architectural shifts. Basing on the chemical and petrographic studies, we are able to indicate the type of used.
Dealing with lime and sand plasters, it is possible to determine weight ratio: filler to binding agent, while petrographic joints analysis provides the answer to the question concerning volumetric ratio.
We also run qualitative and semi-qualitative analyses of salts. Determining degree of salinity of the plaster plays a crucial role in planning conservation works.
Photomicrograph of a thin section of plaster in cross-polarised light.
FIBRE IDENTIFICATION
is a necessary element of the process of dating and authenticating the work of art. Through the analysis of fibre morphology and how it behaves when exposed? to certain chemical agents we are able to determine the type of used canvas (synthetic, cotton, linen, hemp, jute).
Photomicrograph of linen fiber in transmitted light.