Image stratigraphy with the Multilayer Method (patented)
Painted surfaces are, generally speaking, multilayer structures.
In the conservation field, a few methods are available to investigate such structures, and to permit to image layers which are normally hidden to the naked eye.One of these methods makes use of IR radiation. Analysing the IR radiation reflected by a painting’s surface it is generally possible to see the underlying priming layer and possibly the preparatory underdrawing.
The other methods currently used to investigate the various separate layers, imply microsampling of the painting surface and analysing the cross-section.
However, in this way, there are two main drawbacks. The first is linked to the need of a (micro-)invasive action, the other is related to the fact that the results are valid only for that specific sample, and cannot be generally extended to the neighbouring surface.
The method we propose is intended to provide a qualitative image stratigraphy of the varnish and superficial paint layers , overcoming some of the previously mentioned weak points of the currently used techniques.
This new procedure makes use of UV induced visible fluorescence multispectral imaging and exploits the fact that different materials fluoresce, reflect and absorb light in different ways, and electromagnetic radiation in the visible range has a different penetrating power depending on its wavelength.
The result of this process is a set of images. In each of them a different layer is visible. The current results have found immediate application in the conservation field