ABSTRACT
Other factors include opaqueness, transparency and colour changes that some pigments undergo when mixed with some media, as well as the proportion of pigment to medium in a given mixture or even optical effects and appearances that varnishes, waxes, glairs, and gums produced on the resulting work over time. For example, blue pigments are very often more affected by media. Two accounts are given by Thompson (1956: 56-57) that exemplify the influence of media on the resulting colour appearance. The first is “Livro de como se fazen as côres”, written in Portuguese, but in Hebrew characters in the fifteenth century or even earlier says to temper dark blues with gum; but for light blues to add white lead and temper with glair. Mixtures of gums and glair were often
1 INTRODUCTION-THE APPEARANCE OF A PAINTING
Painting is a small part of the whole subject of Medieval and Renaissance art, even though extremely complex. Its complexity involves the origins of a particular technique, periods of its use in different regions, stylistic and technical developments, inventions, circulation of literature and documents regarding materials and technical procedures, some of which considered secret. Thompson’s “Materials and Techniques of Medieval Painting” (1956) is an extraordinary account of carriers and grounds; binding media, pigments and metals with descriptions of technical aspects, clarification of effects and functions, variation of methods, craftsmanship, particularities of media and characteristics of the composition of materials, their applications, with and extensive chapter on pigments1.
