Investigations in Birkenhead have uncovered remnants of the Wirral’s industrial past, shedding light on previously obscure industries such as smalt-production.

An aerial view of the excavation site near the docks at Birkenhead. [Image: Chris Wild, Salford Archaeology]

Smalt is not a commodity that attracts much demand in the modern world, but it was a crucial raw material for several 19th-century industries, used as an intense colouring agent. It is an inorganic pigment that contains 2-18% cobalt oxide and 66-72% silica, manufactured by mixing cobalt oxide with molten glass and then grinding the result to create a coarse pigment with a distinctive deep blue colour.

The finer details of the 19th-century smalt-manufacturing process are largely undocumented, however, and few archaeological investigations of smalt works have been carried out, meaning that modern understanding of the industry is poor. A unique opportunity to redress this knowledge gap arose, though, with the redevelopment of disused land along the docks at Birkenhead (as an initial phase of a major regeneration scheme known as Wirral Waters, led by Peel L&P). This triggered an archaeological investigation by Salford Archaeology within the University of Salford, which focused on the footprint of several 19th-century industrial sites, including the former Seacombe Smalt Works.

The Works were established on a small scale around 1808. The site’s early years of production were beset by financial difficulty and insurmountable technological challenges, until it was taken over in the 1820s by Messrs Mawdsley and Smith. Thereafter, it operated successfully until the death of one of the partners in 1860, which led to the Works’ closure and subsequent demolition. The only survey at a reasonable scale to capture the Seacombe Works is a tithe map of c.1841, which provides a block plan but no indication of the uses of the component buildings.

Excavation held the key, revealing that the manufacturing processes had been focused within a single, irregular-shaped building in the centre of the Works. Structures of particular note include four circular brick floors, which probably represent the bases of ovens in which the cobalt ore was roasted to drive off unwanted contaminants. This was then mixed with potassium carbonate, saltpetre, and fine sand as a source of silica in the long wooden tanks that were exposed immediately to the south of the ovens. The resultant batch would have been fused together by exposure to high temperatures in a furnace, the foundations of which were excavated at the eastern end of the building, and finally the hot glass would have been immersed in water, causing it to shatter into small pieces that were then ground to powder.

Uncovering the foundations of the smalt works shed new light on the structures used at different stages of the process, such as this furnace. [Image: Chris Wild, Salford Archaeology]

The southern part of the excavation area contained the foundations of workers’ housing. At least 15 houses were identified, which corresponds with the 1841 and 1851 census returns. These had been built by Messrs Mawdsley and Smith to create what was essentially a ‘factory colony’.

Text by Andrew Radford and Ian Miller


This news article appears in issue 365 of Current Archaeology. To find out more about subscribing to the magazine, click here.

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