Extended Abstract of invited Lecture Gardiner Museum, Toronto, Canada, September 25th, 2019.
Porcelains are first and foremost an exercise in materials science - body, glaze, and painting. The understanding of that contribution to Western porcelains is, after many years, becoming a major contributor in reaching a more holistic understanding of these ceramics - raw materials, firing conditions, glaze compositions, attribution, dating, and technology transfer pathways set against a better understanding of historical documents and societal conditions of those times. Such studies appeared with the development of gravimetric chemical analyses by the late 18th C and these initial analytical attempts appear to have grown out of alchemy, burning mirrors, and the assaying of metalliferous deposits through the use of furnaces.
Early ceramic analysts included Brongniart, Klaproth, Vauquelin, and in the UK during the 19th C, Simeon Shaw, Sir Humphrey Davey, and Sir Arthur Church. It appears that Nicholas Vauquelin was the first to undertake full gravimetric analyses of a Hessian crucible and various associated raw materials by 1799. Subsequently, Brongniart at Sèvres by 1844 undertook analyses of a wide range of wares and even writing to Silliman's Journal (American Journal of Science) for donations of North American ceramics including prehistoric wares to a collection he was building at Sèvres dedicated to the Art of Pottery.
In Britain Simeon Shaw initiated gravimetric analyses of Staffordshire ceramics and hard-paste porcelains from Europe (Meissen, Vienna, Sèvres, and Berlin) by the 1830s. An early summary of British ceramics including full chemical analyses was that by Sir Arthur Church in his Cantor Lectures (1880-1881). Subsequently Eccles and Rackham (1922) undertook a range of analyses of English porcelains and divided these ceramics into five groups based on their compositions.
- phosphatic, bone ash
- magnesian, soapstone
- calciferous, glassy
- hard-paste
- hybrid hard-paste
By the mid-1900s spectrographic analytical methods were applied to ceramic bodies, an example being the analyses of two George II busts by Watney in 1968. This was followed by the application of X-ray diffraction (XRD) to identify the mineral composition in various porcelain bodies by the British Museum Research Laboratories. Modern analytical methods are now non-destructive and these include SEM with energy dispersive attachments and variable chamber pressures, hand-held XRF, and Raman spectroscopy among other techniques.
Scientific analyses of the Burghley House jars are discussed and our deduction based on historical documents and compositional science, is that these jars highlight the most significant fallacy in Western ceramic decorative arts, in that these refractory and high-fired porcelains pre-date Meissen by some 35 years as shown by Morgan Wesley. Based on the balance of probability we contend that the author of these porcelains was John Dwight, widely regarded as a failure when it came to porcelain production.
Our research into the 'A'-marked porcelains has resulted in the identification of the most likely raw materials used, coupled with analogue firing of the porcelain body, an attribution, and a dating of these refractory wares to Bow in the early - mid 1740s. As one commentator has noted,
But it has gone further, because its corollary is that automatically it must lead to a re-assessment of the assumed premier position of Chelsea, an assumed position which has dominated English porcelain scholarship for very many decades.
Our analyses and those by Dr W. Jay of Limehouse porcelains and wasters recognise that wares of the magnesian-phosphatic composition are not Limehouse and a discussion is given as to where these wares best fit. Likewise analytical science has demonstrated that crazed, so-called Broad Street Worcester porcelains are magnesian - phosphatic-lead (Mg-P-Pb) in composition and better reside as early Lund's Bristol. Our science supports the initial work by Owen and Hillis who have shown that there is a close link between early Bow and William Reid of Liverpool and this technology pathway now includes the manufacture of a newly recognised refractory, aluminous (15-20wt% Al2O3) bone-ash body at both factories. This in turn supports the argument by Victor Owen that the classification of English porcelains, both so-called hard-and soft-paste, needs to be revised as the traditional classification dating back to Eccles and Rackham - soapstone, bone-ash etc - is too limiting. An analogy can be drawn with possible attempts to classify English porcelains based on but five decorative features - in the white, underglaze blue, famille rose, famille vert, and polychrome flowers.
Closer to home, research into Bartlam's porcelains from Cain Hoy, South Carolina demonstrates a good confluence between archaeology, science, historical documents, and connoisseurship. We suggest that John Bartlam 'pirated' the Bowcock period recipe used at Bow 1755-c. 1770 and replicated it at Cain Hoy. Currently, analytical science is helping to arrive at more secure attributions for a number of factories including Bovey Tracy, Isleworth, William Reid, and Chaffers Liverpool.
Raman investigations into European ceramics were pioneered by Colomban and co-workers while in the UK, K. A. Leslie appears to have been the first to utilise Raman. Professor Howell Edwards has applied such studies to Nantgarw and Swansea porcelains to gain a more holistic understanding of these wares. More recently Jay and co-workers using Raman and SEM studies have recognised the use of Carrickfergus magnesian clay in Lincolnshire ceramics, thus identifying trade routes out of Ireland and demonstrating that not all magnesian ceramics must contain soapstone.
Claims, often out of Britain, still question whether science has a role in understanding and interpreting ceramics. To this end Edwards (2018, Chapter 9) highlights the current division between scientific analyses and expert opinions based on visual examination of porcelains or as David Battey (1994) has argued, the eyes have it. Edwards points out,
I think experts can see science as challenging their hierarchical authority and they vigorously defend that perceived assault by rubbishing it or simply downgrading it ! (Edwards, pers. comm. July 2018).
We wonder whether scientific input would have recognised and exposed a number of alleged recent ceramic fakes such as a Chelsea bust of a young girl, all apparently enthusiastically accepted by ceramic connoisseurs. Based on science and porcelain composition, and not on decorative idioms, the shade of grey in the glaze, or the presence of pinholes in the glaze, the overriding conclusion we have come to is that the English porcelain tradition is pre-eminent in the Western world, pre-dating Meissen to produce a refractory porcelain body or bodies. This tradition in turn has led to the production of a plethora of English porcelain bodies both lower-fired and refractory using combinations of primary and secondary clays, bone ash, soapstone, and lime-bearing frit. This tradition has in the past suffered under what we believe to be an inherent inferiority complex among English ceramic experts based on notions that their porcelain tradition is essentially derivative being handed down by wandering Continental gardeners/potters.
In summary, modern analytical science is contributing to a holistic understanding of porcelains, an approach that mere visual inspection could never hope to imitate. The impression that we have is that the ceramic community in North America is far more receptive to such an approach than in Britain today.