Tales from the Bottle: Exploring the legacy of English glassmaking

Dark brown or green glass bottles from mid-17th – 19th century are frequently described in the literature as black glass. Vessels made of such glass were a major output of English glassblowing industry, that was responding to the booming industrialization and the demands of Atlantic trade. Unfortunately, relatively little information about English black glass is available to researchers, since before the second half of the 19th century there were no specialised price lists or illustrated catalogues for this type of product . Thus, even for complete and sealed bottles the provenance analysis is frequently very complicated, becoming an almost impossible task for fragmented artefacts or glass tools. Establishing the provenance of such glass artefacts found, for example, in enslaved African contexts (e.g. St. Kitts or Jamaica) will allow to uncover more details about the local economy of the Caribbean and lived experiences of the people, usually underrepresented in the written records of this era. Additionally, due to its durability and omnipresence, glass can be effectively used as a global trade route tracer, helping to discover previously overlooked economic relations.
It’s been established, that the chemistry of glass may provide some insights into its provenance, but no systematic studies of this kind are available for the 18th century English black glass. Since in early modern Europe the transfer of manufacturing technologies and glass recipes was relatively rapid, the knowledge of just major chemical elements and their proportions in the bottle glass is unlikely to be sufficient to identify an artifact as definitively English, French or Dutch. Thus, we aim to apply a geomaterial-centred approach, using the trace elements (present in quantities of < 0.5 wt%) detected in the black glass to pinpoint its geographical origin. We theorise, that the raw materials (alkali, sand, metal oxides) for such cheap glass were sourced from local English or Welsh mineral deposits, with each deposit and material type having individual discernible geochemical fingerprints i.e. the presence of certain trace elements and their proportions.
To confirm this hypothesis, we will analyse samples of the 18th century black glass and some geological materials, known to be used in English glassmaking of this period. We will use the chemical data gathered using non-invasive & non-destructive method (portable XFR, Vanta C Series Handheld XRF spectrometer) from 18th century English bottles preserved in the collection of Bristol Museum and Art Gallery and our knowledge of English mineral deposits & glass technology to answer the following question: can we establish the link between the sources of raw materials used for black glass manufacturing and utilise this knowledge for provenance analysis? The archaeomaterials investigation will be supported by archival research, that will help to establish such connections for English and particularly Bristolian glassmaking history. We aim to use the analyses of signed and dated Bristol Blue Glass from the collection of Bristol Museum and Art Gallery to benchmark our geomaterial identification and possibly pinpoint Bristol-specific materials that went into the glass production.