2006:608 - DUBLIN: Mercy Convent, Cork Street, Dublin

The site at Mercy Convent, Dublin 8, is bounded by Cork Street, Ormond Street and Brickfield Lane. Testing carried out by Eoin Sullivan in October 2000 (Excavations 2002, No. 255) did not reveal any archaeological remains. However, the presence of inhabited buildings at the time had limited testing only to certain parts of the site. During the demolition of these buildings, the remains of a tanning box were revealed in the north-western part of the site and additional testing carried out by Eoin Corcoran in December 2004 (Excavations 2004, No. 529) revealed a second box in the same area.

Several post-medieval features were excavated by Ruth Elliot in the adjacent area during monitoring and excavation carried out between 4 January and 11 February 2005 (Excavations 2005, No. 427), the majority of these features relating to an early 19th-century water system comprising wooden pipes, drains, cisterns and a capillary pump.

Further monitoring and excavation in advance of the construction of various service trenches was carried out in stages in the north-western part of the site between 1 March 2005 and 1 September 2006. Several features of post-medieval date were identified in theses trenches, the majority of which appeared to be related to the production of leather and were clearly evidence of the mid-19th-century tannery yards marked on the 1866 OS map.

Four mortared red-brick structures, filled with a malodorous mix of plant fibres and lime, were identified as liming tanks. Prior to tanning, the hides would have been washed and then placed in tanks containing lime and water, which would have removed any remaining hair, flesh and fats that adhered to the hide.
After liming, the hides were immersed in a series of tanning boxes containing acidic ‘tanning liquor’ – solutions of water and tree bark. A large number of these tanning boxes were identified in this area. These were plank-built rectangular boxes with an average size of 1m wide by 1.4m long and 0.6m surviving internal depth. The boxes were arranged in parallel rows with a distance of c. 0.25–0.3m between each box, on a layer of sticky gley clay, which lined the base of large straight-sided pits, measuring 2.8m in average depth from the modern ground surface. The gley clay lining may have been to help prevent leakage of ‘tanning liquor’ from the tanning boxes into the underlying subsoil. The spaces in between the boxes were backfilled with the excavated clay from the pit.

The remains of a mortared, stone-built structure in a very disturbed and damaged condition were identified at the northern edge of the site. Although only three sides of this structure were visible, it appeared to be a square-shaped tank formed by mortared stone walls with internal wooden lining, the interior of which was filled with a malodorous deposit of reddish-brown wood fragments mixed with pockets of purplish-brown humic soil. The structure was constructed within a straight-sided foundation cut, the base of which was located at a depth of 3.6m from the modern ground surface. This was probably a tanning tank used for the production of thicker leather than that produced in the smaller plank-built boxes. The hides would have been arranged with alternating layers of tree bark (probably oak) until the tank was filled.

The remains of two north–south-aligned drains running between the tanning pits also appeared to be contemporary with the tannery yard.

Excavations were also carried out at the east edge of the site, in a garden area at the front of the convent chapel, but this revealed no activity of archaeological significance.

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