As the Ashmolean collection of Raqqa vessels demonstrates, "Raqqa" is a term used to describe a diversity of painting styles, decoration types, and glazing, and may even represent more than one group, from various centres of production in Syria and Persia. Lustre-painted ware is one of six types of wares commonly ascribed to Raqqa. Yet even within the lustrewares there is enough variation to question whether they are all products of the Raqqa potteries. Scholars have compiled lists of characteristics, which often do not apply to all of the lustre vessels known. For instance, Lane asserts that the lustre paint used "always has a very distinctive chocolate-brown tone," which Fehervari echoes but is contradicted by Caiger-Smith and by the vessels in the Ashmolean collection, as well as those I have observed in the Victoria & Albert Museum. The quality of painting varies noticeably, with samples like dish X3068 being finely executed, while others are more haphazardly decorated, like jug 1978.2172. Other differences can be found in the motifs chosen and style of painting, the thickness and skill of the potting, the composition of the vessel body (a few vessels in this collection are actually of earthenware), and the quality of the glaze.
Another problem with identifying Raqqa wares has been Museums necessary reliance on collectors. Antiquities merchants cannot always be trusted to provide the most accurate information, and doubtless there are several vessels for which Raqqan provenance has been falsely or mistakenly claimed. The vessels then have to be identified from what we know of the sherds and wasters recovered by Sauvaget in 1924, and more recently by Michael Meinecke and the University of Nottingham excavations led by Dr Julian Henderson, not all of which have been published. Since Sauvaget excavated unstratigraphically, the primary evidence for proving that lustre was produced at Raqqa is one vessel primed for lustre and bearing a dateable inscription which, again, has been improperly published.
Robert Mason has identified a petrographic profile for many vessels that are claimed to have come from Raqqa, and shown that a variety of decorative styles have the same petrographic profile. This technique, done by examining a thin slice of pottery through a polarising petrographic microscope, provides an identification of the rocks and minerals present in the clay. The eventual aim is to make a match between the pottery and soil samples of possible production centres. Mason sampled two groups of stonepaste wares said to be Raqqa manufactures: a collection of lustre-painted sherds from excavations at Abu Sudaira in Iraq by Gerald Reitlinger, and a group of vessels, including wasters, in the Royal Ontario Museum. Only two sherds of the latter group were lustre-painted. He found the petrographic profiles of both these groups to be identical. Mason concluded that the types of wares normally attributed to Raqqa could indeed be identified as having the same point of origin. The exception was "Raqqa-style" underglaze-painted wares, which he suggests may actually come from Damascus. He also sampled pieces from Tell Aswad, a site immediately adjacent to Raqqa, which contains many kilns and much pottery. Several of the pieces he analysed were glazed, but none had lustre decoration. Mason identified four Tell Aswad fabrics and hypothesised that they were manufactured in or around Raqqa. Obviously it cannot be proved that the Ashmoleans collection of Raqqa lustres indeed comes from Raqqa without similar analysis of each vessel. Masons results do suggest the possibility that despite the diversity of style, these pieces could be Raqqan. There is no evidence otherwise, so for the time being they preserve their claim.