19 washed areas in differing thicknesses and strengths. Blue-painters face the task of applying colour in thicknesses conducive to the best decorative effect despite not being able to see the outcome until the piece has been glazed and fired. The final outcome is crucially dependent on the blend of paint and the first firing. The ceramic body must not be fired too highly, otherwise it will be insufficiently absorbent and the blue will be too pale.19 The porcelain is then glazed, a process in which the porous ceramic body soaks up the liquid glaze and the white coating formed obliterates the decoration in its entirety. Only once subjected to glost firing at around 1,400 degrees Centigrade does the glaze become transparent and reveal the cobalt blue in all its lustrous brilliance. Firing transforms the blackish-grey of cobalt oxide into a dazzling blue colour whilst the porcelain body shrinks in size by about 16 per cent. 1 UAStPMM I A f2 fol. 180. 2 Boltz 1990, p. 137; Weber 2012, vol. II, p. 10. 3 Counting teabowls and saucers separately, the total comes to 6,058, see Lubcke 2018, p. 35. 4 Miedtank 2014, pp. 2. 5 Ibid, p. 3. 6 Ibid, pp. 3. 7 Ibid, pp. 16. On Horn: information kindly provided by Christoph Kirsch on 9. 5. 2014, Langeloh Porcelain, Weinheim. 8 UAStPMM: Köhler’s book of recipes, Pretiosa no. 3. 9 Mields 1960, pp. 329. 10 A number of notebooks, test logs and loose leaves exist – all in all, seven documents in book form by Stöltzel, Köhler, Höroldt, Hoppe, Schubert and others. They cover the secrets or arcana of producing porcelain, colours and glazes. 11 Mields 1960, pp. 349. 12 Steinbrück 1717 (1982), p. 73. 13 Rückert 1990, p. 51. 14 UAStPMM IAa 7 fol. 19, 19b, report dated 12 February 1724. 15 UAStPMM IAa10/323, BA IAa12/334. 16 UAStPMM IAa 1a fol. 187a, submission dated 7 June 1719. 17 UAStPMM IAa 12 f./156. 18 UAStPMM IAa 20/4. 19 Mields/Lauschke 1965, p. 47.
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