A Fragile Heritage
Aspects of Historic Glass
Cambridge - Wednesday 6th September 2017



Craig Kennedy
<Craig.Kennedy@hw.ac.uk>

article posted 4 Apr 2017

Craig Kennedy is Associate Professor of Building Materials at Heriot Watt University, Edinburgh, and has spent his research career in the field of heritage science, undertaking scientific analysis of historic materials in order to allow evidence-led conservation practices.

His co-authors are:

K. Robin Murdoch, Principal and owner of Harlaw Heritage, a consultancy firm that specialises in historic Scottish glass

Tom Addyman, Principal of Addyman Archaeology. This is now one of the leading archaeological companies in the north of Britain concerned with historic building, recording and analysis.

Maureen Young, Conservation Scientist at Historic Environment Scotland, who specialises in undertaking investigations in to built heritage with a view to providing best practice advice for conservation.


Characterisation of Scottish laboratory glass from the 18th and 19th centuries
Craig J. Kennedy1*, K. Robin Murdoch2, Tom Addyman3, Maureen Young4

In Scotland, the teaching and research of chemistry grew throughout the 18th and 19th centuries, particularly at the Universities of Glasgow and Edinburgh. The laboratories at the University of Edinburgh from that period were utilised by very prominent Scottish scientists including Professor Joseph Black, who is credited with the discovery of carbon dioxide.

Items of glass equipment that were used in the laboratories at the University of Edinburgh in the 18th and 19th centuries were assessed elementally using portable X-ray fluorescence techniques. These samples came from two sources: the Playfair Collection, currently under the care of the National Museum of Scotland, and archaeologically excavated glass samples.

In 1858 Professor Lyon Playfair donated a number of items from the chemistry laboratories of the University of Edinburgh to the Industrial Museum of Scotland. These items - termed the 'Playfair Collection' - consisted of laboratory equipment used by Professor Playfair's predecessors as Chair of Chemistry at Edinburgh: Joseph Black (1766-95), Thomas Charles Hope (1795-1844) and William Gregory (1844-1858).

In 2010 Addyman Archaeology was contracted by The University of Edinburgh to undertake assessment and archaeological investigation of the interior courtyard of Edinburgh University's main building complex, known as Old College Quadrangle. From these investigations, scientific glass samples from the laboratories that were not part of the Playfair Collection were excavated.

A high degree of elemental commonality was observed between the samples of the Playfair Collection and the Old College Quadrangle excavations. Samples were divided into three broad categories: high lead glass; moderate lead glass; and high calcium glass.

High lead glasses contained over 30% lead oxide along with small amounts of arsenic and potassium. The high calcium glasses contained over 20% calcium alongside magnesium, aluminium, strontium, iron, titanium and sulphur. The moderate lead glass contained less than 25% lead and also included strontium and iron which were not observed in the high lead glasses, indicating that cullet from another glass type may have been used to manufacture these items.

High levels of lead were observed in thermoscopes, a voltameter, light boxes, bottles and a condenser; items that require thermal stability and a high degree of transparency. High levels of calcium were observed in samples of bottles, vessels, curcurbits and flasks; items that may have been used to hold and store chemicals and, as such, would require a high degree of chemical stability.

These items suggest that Scottish glassmakers of the 18th and 19th centuries were capable of producing high quality bespoke items of a relatively unusual nature, and using unusual ingredients in the melt.

Institutions:

1 Heriot Watt University, Riccarton, Edinburgh, Scotland, UK

2 Harlaw Heritage, Balerno, Scotland, UK

3 Addyman Archaeology, Simpson & Brown Architects, Edinburgh, Scotland, UK

4 Historic Environment Scotland, Conservation Directorate, Edinburgh, Scotland, UK