The southernmost of the Summerlee blast furnaces being brought down by gelignite in 1938 The southernmost of the Summerlee blast furnaces being brought down by gelignite in 1938

Rediscovering Summerlee Iron Works

5 min read

Situated in Coatbridge near Glasgow, Summerlee is the only excavated Victorian iron works in Scotland. The site is legally protected as a Scheduled Monument.

Buried under several metres of debris for half a century, the remains of parts of the works saw daylight again during excavations in the 1980s.

The Summerlee Iron Works was one of the first of a new generation of factories producing pig iron using the revolutionary ‘Hot Blast Process’ which had been patented by James Beaumont Neilson in 1828. This process was more efficient than the old ‘cold blast’ method of making iron and enabled the plentiful local supplies of black band ironstone to be used for the first time. The works flourished in the mid-1800s but went into decline later in the century, eventually closing during the Depression of the early 1930s.

The major structures of the iron works were demolished in 1938. Further demolition and landscaping was carried out in the 1950s when the Hydrocon crane factory (now the main Exhibition Hall  of Summerlee Museum) was built.

After it had been decided to start a museum on part of the iron works site, excavations were begun in 1985 by the Manpower Services Commission. In the first year there was not a full-time archaeologist on site and not all finds were properly recorded. However in 1986 and 1987 more co-ordinated excavations took place. In 2000, Glasgow University Archaeology Research Division (GUARD) dug four trenches to look closer at some parts of the site and the following year Scotia Archaeology made a topographic survey of the site.

 

Excavating Industry

Some of the people involved in the Summerlee excavations, 1980s

Some of the people involved in the Summerlee excavations, 1980s

 

Archaeologists and antiquarians have been excavating ancient sites since at least the 1700s. However since the 1960s they have started to turn their attention to the study of the more recent past: industrial archaeology.

Why bother to dig up sites that are not really that old? Well, Britain was the first nation to go through industrialisation, a process which is changing the world even today. Most early business records have been lost and industry was only rarely recorded by artists so sometimes the best evidence we can get is by digging.

The new interest in industrial heritage was shown by the campaign to save the famous portico at the entrance to Euston Station in London in 1962. The ‘Euston Arch’ was eventually demolished but public attitudes had changed forever.

Scotland’s past is not all about castles and country houses. The iron works, mines, mills and engineering works that employed millions of Scots are often forgotten. Today the world’s only intact preserved 19th century pig iron works is in Germany and is a World Heritage Site.

Summerlee Iron Works: the Site

Summerlee Iron Works Plan

Plan of the Excavations on the Summerlee Iron Works site. The line of stoves and furnaces runs horizontally across the middle of the photo.

 

The iron works had two distinct levels:

On the higher ground where the Summerlee Museum Exhibition Hall is now and as far as the former Caledonian Railway line that runs through Coatbridge Central station, was the infrastructure to bring in the raw materials. These were transported by rail and there were many sidings for wagons. Also up here were the workshops and offices, two reservoirs supplying water for the boilers and for cooling purposes, and the hoists used to transport the raw materials to the tops of the furnaces.

The lower level was where the iron was made in blast furnaces and where the hot blast for the furnaces was generated. Between the furnaces and the canal were the casting beds where the molten iron from the furnaces flowed into sand moulds and solidified. The iron was then taken away on railway wagons alongside the canal and via barges on the canal itself.

 

Summerlee Iron Works from the south. Just off camera to the left the access road to the works (now Heritage Way) runs parallel to the Gartsherrie Burn with the Gartsherrie Branch of the Monkland Canal to the right.

 

This photograph appears to show the Summerlee furnaces being reconstructed. The iron works was served by a branch of the Caledonian Railway but here we see wagons of their rivals the North British Railway.

This photograph appears to show the Summerlee furnaces being reconstructed. The iron works was served by a branch of the Caledonian Railway but here we see wagons of their rivals the North British Railway.

The Blast Furnaces at Summerlee

The furnaces were at the heart of the ironworks: this was where the iron was made. In the hottest part of the furnace temperatures reached 1,300 degrees Celsius.

Rising approximately 20 metres, the furnaces were fed with raw materials at the top (the furnace mouth).

In Scotland it was common practice to build blast furnaces at the bottom of a rise known as a furnace bank. This made it easier to transport the raw materials to the top. At Summerlee the furnace bank wall survives, although it was considerably rebuilt in the 1950s and 1980s.

 

The partially-buried furnace bank wall at Summerlee during excavation in the 1980s

The partially-buried furnace bank wall at Summerlee during excavation in the 1980s

When the works were demolished in 1938 the furnaces were brought down using gelignite at their bases so that they collapsed and broke up.

The southernmost of the Summerlee blast furnaces being brought down by gelignite in 1938

The southernmost of the Summerlee blast furnaces being brought down by gelignite in 1938

Only the furnace hearths still stand to any height but on two of the four excavated furnace hearths you can still see the ‘tap holes’ from which molten iron poured out of the furnace and onto the ‘casting beds’ where it would run into moulds and solidify into long ingots known as ‘pigs’.

 

The Hoists

Raw materials arrived by railway wagon. They were then transported from the top of the furnace bank to the furnace mouths using large handcarts. The carts and the men pushing them were carried up to the top via hydraulic hoists. These were a simple kind of lift powered by a hydraulic ram.

You can easily spot the hoist towers in photographs of the ironworks because they were given mock crenelations (battlements) on top.

 

As with most other structures on the higher level of the ironworks site no trace of the hoists is now visible. However, it is possible that remains of the chambers for the hydraulic rams may survive below ground level.

 

‘Charging’ the Furnaces

Originally the furnaces had open tops. However, this was inefficient and dangerous for the workers as flames and poisonous gases billowed out of the furnace mouths. From the 1870s the tops of the furnaces were fitted with a bell-and-cone arrangement that allowed the waste gases from the furnaces to be recycled and used to heat new, larger hot blast stoves. Raw materials would be tipped on top of the bell that closed the furnace. Then, the workers could withdraw to a safe distance while the bell was lowered, allowing the raw materials to drop into the furnace.

 

 

The Hot Blast

Summerlee was one of the first pig iron works purpose-built to use JB Neilson’s Hot Blast Process. Here the air that was to be forced through the blast furnace was first heated in stoves.

The first stoves at Summerlee were small rectangular structures. No trace of these stoves has been found but they can be seen on the first Ordnance Survey map of Coatbridge. In the 1870s new regenerative stoves known as ‘Cowper Stoves’ were installed. These structures were as tall as the furnaces from which they re-used the waste gases. The gases were burned in the stove to heat up a honeycomb of fire bricks. When the bricks were hot enough the furnace gases were shut off and air was pushed into the stove to be heated by the fire bricks. This air became the ‘hot blast’ that was then directed into the furnaces themselves.

 

Cross-section of a Cowper Stove.

Cross-section of a Cowper Stove for heating the hot blast. On the left is a honeycomb of fire bricks which are heated by burning waste gases from the blast furnace.

 

‘Tapping’ the Furnaces

The furnaces were ‘tapped’ by breaking a clay plug that blocked up the ‘tap hole’ in the furnace near ground level.

 

The Pig Beds

The pig iron was cast in the open air. The pig beds consisted of flat areas of casting sand (a mix of sand and clay) into which wooden ‘patterns’ were pressed. These patterns were the shape of the iron to be cast and left an impression into which the molten iron could flow.

 

The Engine Houses

Air for the hot blast was forced through the stoves by powerful steam engines in engine houses at either end of the row of furnaces. The southern engine house at Summerlee has been excavated, along with a later gas engine house. A visitor in 1895 saw an 1836 blowing engine still running but we do not yet know where on the site it was.

The engine house needed very strong stone foundations to withstand the rocking of the engine’s huge cast iron beam and today these are some of the most imposing remains on the site. In 2000 archaeologists dug a new trench inside the engine house and found an early floor layer, fused pieces of machinery and objects that appeared to have been dumped in the engine sump during demolition.

 

 

Traces of Iron

Today, there are very few traces remaining of the coke-smelting iron industry in Scotland but a few sites can still be seen besides Summerlee:

Dalmellington Iron Works, Waterside, East Ayrshire

Besides the very well preserved wall of the furnace bank, a number of buildings survive including the company offices, workshops and a magnificent double engine house which is now derelict and on the Buildings at Risk Register.

Shotts Iron Works, North Lanarkshire

The furnace bank can still be seen, along with the iconic crenelated water tower above it and also the remains of an ore calcinating kiln. The furnace bank and tower are currently on the Buildings at Risk Register.

Calderbank Iron Works, North Lanarkshire

The truncated remains of the furnace bank wall can be seen, despite damage caused by later rebuilding when the site became a major steel works.

 

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