The success of the conservation and restoration process depends largely on the understanding of the physical and chemical makeup of the work of art on the microscopic level. Optical microscopy is a powerful tool in the identification of pigment particles, fibers and other substances. It also allows the restorer to perform microchemistry on extremely small samples. 

Cross  section of a  fragment of  paint showing the layers of  color  as the  artist built up the surface. The small particles, when examined  more closely  tell us how the artist mixed his colors.

The photographs obtained through the microscope are invaluable both in discovery as well as in documentation. The understanding of the make-up of a work of art on the microscopic level not only aids the restorer in his work but also provides insight into its age and origins. 

Two basic types of instruments are used: the optical microscope and the electron microscope. The former is extremely valuable in yielding low-power high-resolution views up to 2000X, the latter in gaining magnifications up to 250 000X. 

The use of special filters and techniques of illumination permit the identification of pigments and fibers. Using large reference sets of known samples, identification is often straightforward and less expensive than spectroscopic analysis. 

Cross section of gesso  from  a suspected  16th. century  picture frame. The section shows that the frame has been re-guilt three times in the past. 

One of the great advancements in microscopy is the in the use of radiation outside the visible spectrum. The above pair of images demonstrate how ultraviolet light causes substances to fluoresce thus giving away important information about their composition. The image on the left is seen in reflected visible light, the one on the right is illuminated by long-wave ultraviolet radiation.
 

Electron microscopy is one of the most powerful analytical tools today. Capable of imaging atoms, it permits the examination of trace amounts of impurities in pigments. We had acquired this instrument in 1980. It has contributed greatly to numerous research projects.