In the production of high-quality Nymphenburg porcelain, the process of firing is at least just as important as the balanced composition of the basic materials. Following the initial mild firing, the raw porcelain items are hardened at 950°C. Then, a thin layer of glaze is applied by hand and the item is subsequently fired again at temperatures of up to 1,400°C during a process that may last up to 36 hours. The glaze fuses with the porcelain during this process, which is called glost firing. The result is the pure white, particularly smooth and hard finish for which Nymphenburg porcelain is known. Only when the mixture of the paste and the firing methods have been coordinated perfectly with each other, is it possible to achieve the porcelain's desired purity, translucence and brilliance in the glaze. The porcelain shrinks by around one sixth during firing. That's why the original patterns are so important: this shrinkage means that a new model cannot be made from a piece of porcelain that has been fired – each mould would produce an end result that would again be 17% smaller. After it has been painted, the porcelain is fired for the last time. The glaze fuses with the paint during this firing, the colour firing, which is effected in stages at temperatures ranging from 1,300 to 760°C. The colours change greatly during this process. And so great demands are placed on the painters who must be fully versed in how the colours must be mixed and applied and how they develop during firing. Five colour firings are required for Nymphenburg's Belle Epoque service, premiered at the 1900 world exhibition, to make the artistic on-glaze painting blossom.