The Methods and Techniques Used by Museums
Science & Tech Editor
Time has an undesirable effect on a painting, just like it has on the body. Indeed, in art work, it involves physical and chemical changes, such as cracking, gradual fading of pigments, varnish discoloration, stretching and narrowing of the canvas to name a few. Furthermore, the situation is worsened when vandalism or neglect enter the equation.
Modern restorers employ examination techniques invisible to the eye. These include X-rays, ultraviolet light, infrared light, particle accelerators, chromatographs, digital milling, 3D digitization and electrical microscopy, as well as other material analysis methods. The aim is to determine the structural constituents of the masterpieces in order to decipher the layers that led to its creation. This knowledge is crucial in determining solutions for the restoration and conservation of the artwork.
Thus, the specialists set up the complete technical file of the artistic piece using pigment analysis, cross section of the pictorial layer and other information gathered. The next step is preventive conservation, since inadequate maintenance conditions can sometimes do more harm than time itself. Indeed, humidity, temperature, climatic fluctuations, and light can always damage the masterpiece.
As such, the purchase of a lux meter (which measures light levels) is often primordial, because some artistic pieces suffer from an extreme sensitivity to light. In particular watercolors, prints and textiles. Because of that, some showcase lighting systems have an electronic eye connected to a timer so that it only becomes lit in the vicinity of visitors, doubling the exposure time while respecting established standards.
When the previous steps do not work, a restorer appears as the final option. First, cleaning requires lightening varnish and then extracting the old layers that the analysis has put forward. Removal of the transparent coating can then be done partially or totally, in case the paint layer or glaze gets damaged. Moreover, when the varnish “yellows”, molecules of resin come into contact with oxygen in the air and form macromolecules.
A suitable solvent will dissolve the varnish without altering the pigments. This dissolves this additional layer without chemically transforming it. Hydrocarbons, such as alcohol or ether, are solvents of choice. Those are selected on the basis of their solubility. Subsequently, the removal of the repaints is very difficult since it requires a localization of the previous reconstitutions and their suppression.
The restoration of the work aims to complete what is missing. Obviously, the pigments must be the same as the original ones. There are three methods for retouching: the pointillism, the illusionism, and the technique of strategio. The pictorial layers which had been removed with time are then fixed. Finally, the choice of materials is made according to the pigment and the context of the painting.
It is important to note that the restoration of art work is a fine “art”. It is one that must be done carefully, but it must also be done subjectively by considering all the possible ways of restoring the work, and objectively when taking into account the importance of the art’s history.