Ultramarine or Powdered Lapis Lazuli (unfortunately known as “Genuine Ultramarine”[36]) is a fine colour; it may have a slightly purplish tint and need [p179] tempering with green to make a pure blue (whole cake about 18s.).
The Blue in common use in early MSS. (before Ultramarine came into use) has a fine, pure colour, and considerable body: it is more raised than any other colour; it is often seen to be full of little sparkles, as though there were powdered glass in it. It is supposed to have been prepared from a copper ore.
The following note on this blue has been given to me by Mr. C. M. Firth:—
“The blue is Native Carbonate of Copper finely powdered and tempered with white of egg (Vermilion is tempered with the Yolk).”
“The ore is of two kinds, a crystalline of a medium hardness found in France at Chessy, and hence called Chessylite, and a soft earthy kind which is obtained in Hungary, and largely now from Australia. The latter is from its ease of manipulation the best for paint making. It should be ground dry till it is no longer gritty and is of a sky blue (pale) colour.”
“The Blue in MSS. was liable to wash off, but the oil in the Yolk prevented a similar result with the Vermilion. The Blue is identical with the Azzuro della magna (for d’allemaigne) of the Middle Ages. The frequently advanced hypothesis that the blue was due to a glass is based on the accounts of (I.) The Vestorian blue copper ‘frit’ for enamels probably; (II.) on the accounts in sixteenth century of the Manufacture of Smalt, which owes its colour to a glass tinted with Cobalt. This Azzuro is the oldest known Western blue, and was probably employed on Egyptian walls, where it has gone green, as also in Italian Frescoes.”
“The Green tint of the chemical change in the Copper is seen in initials in books too much exposed to the damp. These exhibit a bright green tint in places where the colour was thinly applied.” [p180]
It appears that Yolk, besides being unsuited in colour for tempering this blue, changes it to a greenish colour (the effect of the oil, which forms about 30 per cent. of Yolk of Egg).
WHITE.—The tube Chinese White[37] is the most convenient to use when tempering colours.
“White Line or Hair Finishing” (see p. [183]). Various tools have been recommended for this. A sable pencil with the outer hairs cut away, “the smallest brush” made, and even a fine steel pen. I am inclined to believe that some of the early Illuminators used a fine quill—such as a crow quill, or a goose quill scraped thin and sharply pointed.