Microscopic techniques
Microscopic analysis techniques have been applied to cultural heritage projects from the onset of the 20th century. They offer useful information about the way they various works of art are made (construction technique), as well as the type and morphology of their construction materials.
The information garnered offers substantial contributions to the documentation of works.
All analysis techniques require the use of one of the varying microscopes and the analysis of either the original work or a sample to be examined.
The simplest type of all microscopes could be considered the magnifying glass.
The information that results from the analysis of an object depends on the type of microscopic technique chosen, and can include :
- detailed summary and recording of the succession of the construction layers, called stratigraphic structure
- detection and recording of subsequent tampering or restoration, such as over-paintings, application of new paint, materials used for stabilizing loose layers, etc.
- record of the size, shape, and color of the grains of pigments and their distribution within the color layer
- detection of any damage, like inconsistencies in the varnish layer, cracks, delamination of color layers.
- detection of the type of paper fiber, canvas, wood, pigments and inorganic materials
- deduction of organic material used as a vehicle (binder) for pigment colors, such as linseed oil, egg, or animal based adhesives, etc
Types of Microscopic Techniques
There several types of microscopic methods and techniques. Some examples would be Optical Microscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermomicroscopy, along with many others. Optical Microscopy and Scanning Electron Microscopy are the two types of microscopic techniques that are the most frequently used.
Type of samples required
With the exception of stereomicroscopes, most microscopy techniques analyze samples of the works being examined. Samples can be taken in the form of small particles, for example pigments granules, paper or fabric fibers, or in the form of vertical cross-sections for multilayered sections.
In the case of multilayer samples, they are obtained by a minor vertical incision made either at the edge of a work or another area specifically selected so that the sample contains, if possible, all construction layers from the bottom up. For example, in the case of a painted canvas, a sample would include the canvas support layer and all subsequent layers all they to the uppermost varnish layer.