EMAP_2012_Report_6_1.pdf (7.3 MB) - The Heritage Council

little Irish work has been undertaken on the analysis of the glazes and residues apparent on
crucible since the initial overview of the subject by Moss (1927), although the subject has
most recently been summarised (Comber 2004, 33-6; 2008, 139-41). The most extensive
study on crucible residue remains is for Lagore (Hencken 1950, 237-9). While a few of the
crucibles revealed iron residue but not copper, most tended to show traces of iron along with
copper (ibid.). Hencken, however, concluded that the traces of iron ‘would have come into
the crucibles as impurities in the crudely smelted copper’ (1950, 239).
The use of Scanning Electron Microscopes and X- Ray Fluorescence is allowing more detailed
analysis of crucible sherds. Analysis at Coonagh West revealed that the crucible had added
quartz to strengthen the walls and contained copper and tin alloy along with traces of zinc,
silver and gold (Wallace 2009, 8). Assessment of a crucible from Moynagh Lough revealed
copper alloyed with tin as did a pyramidal example from Borris (Wallace & Anguilano 2010a,
22). Residues of metal were found in the interior of a bronze-working crucible from Lagore
and crucibles and heating trays with significant residues of copper, silver and smaller
amounts of gold have been found at Knowth (Barton & Bayley 2012, 527) and Clonmacnoise
(King 2009, 338). Analysis of a lidded crucible from Deer Park showed the presence of
copper, tin and lead (Bayley 2011, 348). Scott (1991, 3), however, suggests that crucibles
may have occasionally been used in ironworking at this time. Indeed pyramidal crucibles from
sites such as Clonfad and Gortnahown 2 indicate that copper alloy was used in the brazing
process and on both sites crucibles were found which may be linked to the finishing of iron
objects (Young 2009a and Young 2009b).
3.2.2: Heating trays:
There has been some discussion of the possible uses of ‘heating trays’, ‘hot-plates’ or ‘cupels’
which are sometimes found associated with crucibles at various sites such as Woodstown
(Young 2006, 3-4, Young 2008, 2) Garranes (Ó Ríordáin 1942, 134-9); Knowth (Eogan 1977,
74); Moynagh Lough (Bradley 1993, 75-9), and Lagore (Craddock 1990, 185). These objects
are produced out of fired clay and were utilized for heating objects that could not be directly
placed into a fire or furnace. Comber (2008, 140) has suggested that they were most useful
‘during the final fabrication of an object, enabling the melting of solder during filigree
application or the evaporation of mercury during gilding’. The majority of identifiable crucible
fragments from Kilgobbin were of this type and thin section analysis revealed that they were
used for assaying silver (Bolger 2008, 99). Two open heating trays from Deer Park farms
suggested that they had been used to heat copper and tin (Bayley 2011, 348). It is also
suggested that heating plates were also used in the production of enamel (see glass-working
Chapter 4). Examination of the assemblage from Dunnyneil led Young to suggest that a subgroup
exists within flat bottomed crucibles (Young 2006a, 1-9). He distinguished between
dish like vessels and flat bottomed vessels which on analysis had high levels of lead and silver
and variable amounts of copper. While the differing use of these vessels is not entirely clear it
has been suggested that they are likely to have been used to assay silver. In this process
small piece of silver would be melted along with a larger amount of lead producing a refined
metal button in the middle of the vessel which would leave a circular scar (Young 2006a).
The scar resulting from the removal of this button has been interpreted in the past as
demonstrating that these vessels were crucible stands. Assessment of the dish like crucibles
from Dunnyneil indicated they were used for assaying silver with high levels of lead present
(ibid. 3).
3.2.3: Moulds
Both stone and clay moulds were used in early medieval Ireland though the latter were more
popular and easier to shape than their stone equivalents. Stone moulds were most commonly
used to produce bar or oblong-shaped ingots. These were easily carved into a stone block
and may have often been manufactured in ‘open’ stone moulds though bivalve examples are
also known. Many stone blocks have multiple moulds for ingots. One of the examples form
Knowth had cruciform carved into one of the mould bases (Barton & Bayley 2012, 527). A
copper-alloy ingot from Garranes actually fitted into an ingot mould found at the site (Ó
Ríordáin 1942, 100, 108-9) and a soapstone ingot mould from High Street, Dublin, contained
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