One special beauty of French illumination of this date is due to the exquisite treatment of architectural frames and backgrounds which are used to enshrine the whole picture. The loveliest Gothic forms are introduced, with the most delicate detail of tracery, pinnacles, canopy-work, shafts and arches, all being frequently executed in gold with subtle transparent shading to give an effect of relief. From the technical point of view these manuscripts reach the highest pitch of perfection; the burnished gold is thick and solid in appearance, and is convex in surface so as to catch high lights, and look, not like gold leaf, but like actual plates of the purest and most polished gold[130]. The pigments are of the most brilliant colours, so skilfully prepared and applied that they are able to defy the power of time to change their hue or even dim their splendour. [Illustration: Fig. 25. Miniature of the birth of the Virgin painted by the illuminator Jacquemart de Odin for the Duc de Berri. The border is of the characteristic French and Franco-Flemish style; see fig. 28 on page 146.] _Survival of style._ Another noticeable point about the French and Franco-Flemish illumination is the manner in which certain modes of decoration survived with very little alteration for more than a century. Thus we find the blue, red and gold diapers used for backgrounds, and the ivy-leaf pattern and its varieties[131], which had been fully developed before the middle of the fourteenth century, still surviving in manuscripts of the second half of the fifteenth century, and continuing in use till the growing decadence of taste caused them to be superseded by borders and backgrounds painted in a naturalistic rather than a decorative manner[132]. _Costly Horae._ The Franco-Flemish manuscripts of the fifteenth century were in some cases remarkable for the amazing amount of laborious illumination and the enormous number of miniatures which they contain. Some of these, which were executed for Royal or Princely patrons and liberal paymasters, engaged the incessant labour of the illuminator for many years. In these cases he was usually paid a regular salary, and so was relieved from the incentive to hasty work which caused so much inferior illumination to be produced in the fifteenth century. _The Bedford Breviary._