2003:463 - BRENNANSTOWN, Cabinteely, Dublin

This site was excavated from 13 to 25 October 2003 in advance of the construction of a large housing development. The site was the levelled remains of a post-medieval brick clamp. It was located in a greenfield site on relatively flat ground on a slight rise in the natural topography approximately 400m west of the Loughlinstown/Cabinteely River. The site was characterised by a long linear feature running 33.75m north–south by 8.25m. This feature contained almost continual rows or columns containing different fills, which were the result of firing activities within the clamp which would have produced a fairly high number of rough bricks in a relatively short time. Although there is no visible above-ground remains of the clamp itself, the columns of scorching and remnant brick debris scattered throughout the site are clearly visible. The area surrounding the site was cleaned back by mechanical digger and no further evidence of brick deposits or associated structures was encountered.

The clamp is believed to have been constructed in a fairly simple fashion. A shallow concave depression/pit was laid out on a fairly level area. This was filled with large amounts of wood for burning. It is believed to have been gorse, which was readily available on the surrounding hillsides and was known to have been used in clamps in the Dublin area. Interspersed throughout the columns of brick was a dedicated column of coke specially prepared and placed within the columns of brick due to its unique ability for sustained burning after the heat from the underlying wood had lost its intensity. The coke inclusions would continue burning for an extended period of time and eventually be transformed into a very hard concrete/slag-like material when the fuel completed its firing cycle. The coke, being close to the columns of brick, would in some instances have brick burnt into its fabric, so that it was difficult to distinguish entirely between the coke and the remnant brick. Although these columns were well defined and visible at the surface, the true nature of the site was revealed below the surface with a series of exploratory trenches excavated by hand through the length and width of the site.

Trench 1 ran north–south (1m by 36m) through the length of the site from surface to subsoil. Trench 2 ran east–west (1m by 10m) through the width of the site from the surface to the subsoil.

As the clamp was by its very nature an inefficient way to make bricks, there would inevitably have been a high degree of brick loss within the structure. This was the result of highly fluctuating degrees of heat in the clamp at two specific points. The edges of the clamp would realise too little heat, which would not see the bricks thoroughly fired, rendering them of little use. At the centre of the clamp the great concentration of heat would render the bricks into one permanent mould, which would again be of no use.

Upon removal of the bricks, which are believed to have numbered roughly between 3–5000, the feature was then abandoned, as it was usually only made for one specific building project and not for long-term manufacture such as would be seen in a brick kiln. The sample of brick remaining, while poorly made and discarded as a viable building material, does provide a good example of the brick which was manufactured in the clamp. The bricks retain their traditional rectangular shape, with dimensions of 0.24m by 0.1m by 0.07m. It would appear that the bricks, although maintaining a uniform size, were not machine-moulded, as they were very rough-hewn with poor tempering material of silica flecks with small- and medium-sized gravel and with possible coke inclusions, which would help the brick to self-fire in the heating process. There are no maker’s marks on any of the bricks.

There were nine finds recovered from the site, of which eight are from the 18th and 19th century, which is believed to be the date of this site. These included partially corroded iron nails, a clay-pipe stem, an unidentified metal object and several fragments of modern ceramics. A flint side scraper was also recovered. This find is believed to be from a prehistoric period and was mixed in with the feature, bearing no relationship to it. All the finds were recovered from the surface. No finds were recovered from within the clamp itself.

Specialist reports are forthcoming.

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