Mortar Analysis

Event ID 1090028

Category Recording

Type Mortar Analysis

Permalink http://canmore.org.uk/event/1090028

NR 71235 78829 A programme of landscape, buildings and

materials analysis is being carried out at Castle Sween within

the framework of this project. Buildings analysis suggested

that Castle Sween had been constructed with a variety of

phase-specific compositionally-contrasting wood-fired lime

mortars, including both limestone-lime and shell-lime bound

materials. In situ characterisation of these materials across

the site generally supported the phasing narrative previously

suggested by the RCAHMS, where those interpretations were

based on direct stratigraphic relationships. Where those

relationships are more indirect, however, then interpretations

are more problematic. A comparative approach to on-site

materials analysis demonstrated that the secondary postern

gate in the W wall was not coeval with the NW Tower, and

suggested that the secondary buttressing against the NE

tower was likely to be contemporary with the secondary

vaulting within that same structure.

A materials sampling programme was subsequently

instigated at Castle Sween, to allow lab-based investigation

of these constructional materials. The sample assemblage

DISCOVERY AND EXCAVATION IN SCOTLAND 49

ARGYLL AND BUTE

ultimately included 10 mortar fragments, 1 relict limestone

clast, 1 shell fragment, 1 sandstone fragment and 72 relict

fuel inclusions.

Materials analysis of the Castle Sween assemblage

included microscopic thick and thin section analysis of the

mortar samples. These analyses both supported and refined

previous provenance interpretations, demonstrating that all

limestone-lime mortars on the site had been manufactured

from a meta-limestone consistent with very local outcrops,

while the shell-lime mortars displayed evidence of both

C. Edule and O. Edulis lime sources. Temper grades and

fuel taxonomy profiles also varied with constructional

phase/chronology, and a typology of 5–6 phase-specific

compositionally-contrasting mortar types ultimately

emerged from the study.

Archive: NRHE (intended)

Funder: University of Stirling and Historic Environment Scotland

Mark Thacker – University of Stirling

(Source: DES, Volume 19)