What is Illumination
Illumination, in whatever form practiced, can never be properly regarded as anything other than one of the genre into which the art of Poly-chromatic decoration may be subdivided. What was originally termed illumination, was simply the application of minimum or red lead, as a color or ink, to decorate, or draw marked attention to, any particular portion of a piece of writing, the general text of which was in black ink. The term was retained long after the original red lead was almost entirely superseded by the more brilliant cinnabar, or vermilion. As ornaments of all kinds were gradually super-added to the primitive distinctions, marked in manuscripts by the use of different-colored inks, the term acquired a wider significance, and, from classical times to the present, has always been regarded as including the practice of every description of ornamental or ornamented writing.
Even though illuminated embellishments were originally executed on vellum, and later on paper, there is no reason whatever to limit its implementation to those materials; wood, metal, slate, stone, canvas, plaster, all may be made to receive it.
Also, ancient illumination was executed by adding colors to water and some glutinous medium, but modern illumination should be worked in oil, turpentine, fresco, tempura, varnish and by every process in which decorative painting is worked.