CHAPTER XV.
The Materials and Technical Processes of the Illuminator (continued).
| Vehicles used. |
Vehicles used.The coloured pigments of the illuminators. Though mediaeval manuscripts are splendid and varied in colour to the highest possible degree, yet all this wealth of decorative effect was produced by a very few pigments, and with the simplest of media, such as size made by boiling down shreds of vellum or fish-bones[[264]], or else gum-arabic, or occasionally white of egg or a mixture both of the yoke and the white[[265]]. In the main the technique of manuscript illumination is the same as that of panel pictures executed in distemper (tempera). An oil medium was unsuited to manuscript work because the oil spoilt the beautiful opaque whiteness of the vellum and made the painting show through to the other side[[266]].
| Ultramarine blue. |
Ultramarine blue.Blue pigments. The most important blue pigment, both during classical and mediaeval times, was the costly and very beautiful ultramarine (azzurrum[[267]] transmarinum), which was made from lapis lazuli, a mineral chiefly imported from Persia. This ultramarine blue was the cyanus or coeruleum of Theophrastus and Pliny. It is not only the most magnificent of all blue pigments, but is also the most durable, even when exposed to light for a very long period.
| Its manufacture. |
Its manufacture.The general principle of the manufacture of ultramarine is very simple; consisting merely in grinding the lapis lazuli to powder, and then separating, by repeated washing, the deep blue particles from the rest of the stone[[268]]. The process of extracting the blue was made easier if the lapis lazuli was first calcined by heat. This is the modern method, and was occasionally done in mediaeval times, but it injures the depth and brilliance of the pigment, and in the finest manuscripts ultramarine was used which had been prepared by the better though more laborious process without the aid of heat.
| Its great value. |
Its great value.The proportion of pure blue in a lump of lapis lazuli is much smaller than it looks; the stone was and is rare and costly, and thus the finest ultramarine of the mediaeval painters was often worth considerably more than double its weight in gold[[269]].