Non-Invasive Raman Analysis of 18th Century Chinese Export/Armorial Overglazed Porcelain: Identification of the Different Enameling Techniques

Abstract

Six rare porcelains of the Qing Dynasty, in particular, dishes ordered respectively for Philibert Orry, the Duke of Penthièvre and a tureen from the service of Louis XV, with royal coat-of-arms, were analyzed non-invasively by Raman microspectrometry. A coffee pot with a rare decoration attributed to Cornelius Pronk was also analyzed as well as two plates, one decorated with an Imari-style pattern and the second post-decorated in the Low-Countries/Holland. The enamel types and coloring or opacifying agents were identified on the basis of combined Raman and SEM-EDXS analysis previously published as well as new section and surface analysis of five plate samples representative of different technologies (blue-and-white, Famille rose). The use of lead oxide for the preparation of overglaze is demonstrated. For the first time, the use of borax in the blue overglaze according to the recipe from the 1753 manuscripts of French chemist Jean Hellot is demonstrated on Chinese porcelain. This fact, like the use of cobalt free of manganese, demonstrates the use of European ingredients and/or recipes for ceramics exported from China to Europe. The highlighting of the use of different recipes or raw materials for porcelain from the same period can therefore be the signature of different workshops. For instance, three different Raman signatures of red decoration were identified from the hematite vibration modes: very narrow modes for Pronk’ coffee pot and Louis XV tureen, broad for Orry’ dish and intermediate for the others. Three workshops are thus expected. It is interesting to note that the use of arsenic for the realization of white enamels corresponds to the latest objects, made after 1738. China was therefore in the 18th century both an importer of European know-how, design and an exporter of enameled products made with imported technologies to Europe.

Full Spectral Range Raman Signatures Related to Changes in Enameling Technologies from the 18th to the 20th Century: Guidelines, Effectiveness and Limitations of the Raman Analysis

“…Figures 1-3 present the characteristic ceramics and enameled metalworks used as a reference of representative spectral signatures. The selection was made on the basis of hundreds of objects and shards analyzed in the laboratory and in situ measurements for the last twenty years [1][2][3][4][5][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Artefacts have been selected with the following criteria: variety of colors, structural types of pigments, substrates, firing temperature, etc.…”

“…The full spectral range is considered here. Vincennes (France) Palette cup porcelain [21] Sèvres (France) Coffee cup porcelain [21] Comte d'Artois factory(France) Vase porcelain [22] China Dish porcelain [23] X China Dish porcelain [23] X China Tea pot porcelain [24] China Bottle porcelain [24] Swiss Watch gold [15] France Watch gold [15] X China Ewer gold [25,26] France Sèvres (France) Ewer metal [27] Sèvres (France) Palette porcelain [2] Nevers (France) Factory (OA7739, Louvre) [22]; (d) Famille rose plate, Chinese factory (Private Coll. ), circa 1770 [23];…”

“…More information is available in the references. ), circa 1770 [23]; (e) 'Chine de commande' porcelain plate, circa 1740-1750 (R1025, Louvre) [23]; (f) 'Thousand flowers pattern' tea pot porcelain, Jingdezhen Imperial Factory, 2nd half of 18th century (F1429C, Fontainebleau) [24]; (g) Chinese porcelain bottle (TH457, Louvre), Qianlong reign [24]; (h) enameled watch, end of 17th century-beginning of 18th century, Swiss factory (OA10079, Louvre), adapted with permission from ref. [15], 2020, Elsevier Masson SAS; (i) ewer, with painted (detail) and cloisonné enamel on gold body, 2nd half of 18th century (F1467.1, Fontainebleau), Qianlong Imperial workshop [25,26].…”

“…The preparation of enamels has greatly evolved since the 15th century (Renaissance) with the development of European artisanal productions including the empirical knowledge of chemical processes and their circulation by means of the recipe books and later with the huge advances in industries and chemical technologies during the 19th century [17]. Globalization of the enameling technology starts during the 17th century with the longdistance trips and trade of European experts [12,[21][22][23][24][25][26].…”

“…On the other hand, the book by Richard A. Eppler and Douglas R. Eppler published in 2000 [39] presents a complete survey of contemporary enameling technologies. Based on these works and our previous publications [2,4,5,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][41][42][43], Table 2 lists the main structural types of pigments from different historical periods. The different phases are classified according to the criteria used in solid state chemistry and ceramics textbooks [48] for structural types.…”