Igne refutata: Thermal Analysis in the Laboratory Practices of John Dwight. . .
191
Fig. 2 Porcelain sherds, two identified as Green’s type 33 and 34 the other unrecorded, attributed to John Dwight, 1672–1673 (Photograph by the author)
The current whereabouts of the two notebooks is unknown; they were sold through Christie’s, likely in 1888 or 1889. Notices seeking their recovery have been remarked on as early as 30 June, 1894, but no indication as to their location has surfaced.29 While no contemporary records of the tests conducted between 1672 and 1675 are known to exist, laboratory testing of the composition of the sherds found from this period coincide broadly with the recipes given for porcelain in the later texts. This methodology demonstrates the connection between Dwight’s laboratory practice to that employed by Boyle in the late 1650s, and echoes the laboratory books of Starkey.30 Similar to the annotations and refinements demonstrated in Starkey’s laboratory books, we see Dwight actively editing his working notebook with commentary on the effectiveness of recipes and the striking through of less effective formula. Lady Schreiber was rigorous in her transcriptions, making note of pages torn out, recipes struck through, and duplicating marginalia such as a “not very good” accompanying a struck through recipe for “a dark red porcellane or China Cley” dated 14 November, 1693.31 The second, arguably more interesting, group discovered within the context of soakway A18, and thus contemporary to the test chips, was a group of Chinese export porcelain sherds (Fig. 3). Among this group of blue and white sherds, representing at least five distinct objects, are cases where glaze running over fractured edges demonstrate clear evidence of re-firing, at a temperature hot enough to at least partially liquefy the glaze, without burning the cobalt. A final sherd from this group contains evidence of cobalt over-painting by Dwight, before re-firing, perhaps as a test coinciding with the samples of his own work.
29 Schreiber, Charlotte Schreiber’s Notebook, 31; and Haselgrove & Murray, “Dwight’s Fulham Pottery,” 74. 30 For the working practices, see Starkey, Alchemical Laboratory Notebooks. 31 Reproduced in Haselgrove & Murray, “Dwight’s Fulham Pottery,” 73, ai–bviii, 74.