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English delftware (c. 1770) from Bristol, Lancaster and Liverpool: A composition study using Raman spectroscopy and
Howell G M Edwards1, William H Jay2
1Emeritus Professor, School of Chemistry and Biosciences, Faculty of Life Sciences, Bradford University, BD7 1DP, UK.
Summary
Analysis of 18th-century delftware reveals unique MgO-rich clay bodies from Ireland, differentiating West Coast English wares from London types. Arsenic in glazes formed lead arsenate crystals during firing.
Area of Science:
- Materials Science
- Archaeometry
- Ceramic Analysis
Background:
- Delftware, a type of tin-glazed earthenware, was popular in England from the 17th to 18th centuries.
- Production centers in England, such as Bristol, Lancaster, and Liverpool, developed distinct manufacturing techniques.
- Understanding the material composition of delftware provides insights into trade, technology, and regional variations.
Purpose of the Study:
- To non-invasively analyze the material composition of decorated delftware produced in England around 1770.
- To differentiate delftware from different manufacturing regions based on body and glaze composition.
- To investigate the formation of lead arsenate compounds in the glaze during high-temperature firing.
Main Methods:
- Non-invasive analysis using Raman spectroscopy and electron microscopy.
- Chemical analysis of body paste and glaze composition.
- Microstructural examination of crystalline phases in the glaze.
Main Results:
- Delftware from Bristol, Lancaster, and Liverpool contained significant magnesium oxide (MgO) in the body paste, derived from dolomitic clay sourced from Carrickfergus, Ireland.
- This MgO content effectively differentiates these West Coast wares from MgO-free London delftware.
- Glazes contained arsenic, which reacted with lead, calcium, and magnesium during firing to form various lead arsenate minerals, including mimetite and wendwilsonite.
Conclusions:
- The use of dolomitic Irish clay is a key characteristic of West Coast English delftware production.
- The presence and transformation of arsenic in lead glazes are significant features of these 18th-century ceramics.
- Material analysis provides a robust method for provenance studies and understanding historical ceramic manufacturing processes.
Keywords:
Cobalt blue pigmentationDelftwareElectron microscopyLead arsenateLead–tin glazeRaman spectroscopyMore Related Videos
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