The urban back alleys of York, away from the city centre, feature some very distinctive historic paving bricks, mostly in the form of double hexagons linked together, although some are rectangular or square. These bricks have a shiny silvery blue/grey surface, and in some cases are used to line street gutters. They remain a significant feature from the childhood of local people, who have fond memories of playing out on them. 

I was asked about them by a visitor to an event in 2022, which led me to follow up with some research. I soon found out that apart from a paper in 1981 by Cleveland industrial archaeologist Charles Morris, and a few newspaper articles in the north-east press, there was very little background detail. Intriguingly I also discovered some errors about their origins in official heritage reports. Local historians can play a key role in synthesising evidence from other experts such as geologists, industrial archaeologists and even genealogists, and as a result I was able to piece together the story of these bricks, which played a significant role in York’s historic urban landscape. 

They feature all over older areas of York, and our history group is now mapping them across the city. They’re also found elsewhere in north-east England, for example in Saltburn, Darlington and Whitby, and further afield. They are actually called scoria bricks or blocks. The word scoria is an ancient Greek word, meaning excrement or dung, but the Romans used this word for hot lava bursting out of a volcano. Then it became the name of the refuse left when metal was melted. The story of these bricks starts in the mid-19th century, in the blast furnaces in Cleveland in the north-east of England.

Millions of tons of pig iron were being produced, from ore deposits in rock. This  generated millions of tons of slag waste at the bottom of the blast furnaces, a real problem for the ironmasters, as it was expensive to remove. Slag was often tipped on waste ground or used to reclaim marsh land. It was sometimes poured over cliffs, for example at Skinningrove. ‘Basic slag’ was used as a fertiliser on fields, even in the 1950s, as it contained lime and released phosphates when buried. Its chemical constituents were lime, silica, alumina, magnesia, sulphur, calcium sulphide, iron, potash, soda and manganese, and it was the manganese compounds which led to its blue colour. 

A smart Victorian idea was to make shiny silvery-blue bricks from slag for a road or alley surface, a really good recycling solution because of its qualities. There were many attempts at this, but getting the slag into the right place, shaping it into uniform bricks and cooling it slowly was full of difficulties. It was Joseph Woodward, a Darlington man, who found the solution in the late 1860s. 

Woodward’s process tapped molten slag from the bottom of the blast furnaces and transported it in bogies (trucks) along a railway to the kilns. His invention was a revolving table with moulds. The slag was poured into the moulds, and after two minutes, it was still red hot, but set. At the vital moment, the turning motion of the table and a lifting latch tipped the bricks out of the moulds, to be arranged by an attendant onto a conveyor belt carrying them into a kiln, heated by the furnace. Bricks were then housed in this annealing kiln for three days, to make them more workable after cooling. Here they were allowed to cool very slowly, in order to remove internal stresses. This had to be carefully managed to avoid cracking and to maintain an even texture.

The process produced scoria bricks, a kind of basalt, an igneous rock. These bricks were very hard to break, very durable, completely waterproof, frost-proof and indeed chemical-proof. Much later they proved very useful in drainage channels at ICI Billingham in the 1920s. The alternative to using these bricks on Victorian roads was whinstone setts, which had replaced cobbles. It was found that scoria bricks were cheaper and easier to lay, as they were very regular and identical in size, thus easily laid flat on roads, on a 6in bed of sand, to be compressed down by men with heavy wooden rammers.

Joseph took a patent out in 1869 on his device, and recruited a group of businessmen to form the Tees Scoriae Brick Company, which opened in Eston, Middlesbrough in 1872. The company then opened factories at Acklam in Middlesborough and Lackenby at Redcar, next to blast furnaces. Woodward also took out an American patent in 1877.

There were several brick patterns, to be found all over the North East. York alleys and some streets were paved with them in the late 19th century, including for example the approaches to the new railway station at York, which opened in 1877. Huge quantities were manufactured on Teesside, and many were exported to Canada and the West Indies, Holland, Belgium, the US, South America and Africa. Excitingly when I posted about my researches on Bluesky social media last year, I heard from a historian in Philadelphia US, showing me examples of their use there.

Eventually however the motor car destroyed the business, when it replaced metal-rimmed carriages, as people wanted a smoother ride, and tarmac started to follow in the 1930s. Steel and iron making ran down and by 1966 the Company became insolvent, to be wound up in 1972. Sadly now in York, many alleys have been excavated for utilities and street lighting, with scoria bricks patched with tarmac, as the bricks are no longer available for replacement. 

My researches into the background of Joseph Woodward (1824-1888), who played such a significant role in York’s urban landscape, reveal an intriguing man, who moved around the country, changing his occupation and businesses, his residences, and sadly losing a number of wives. Frustratingly a January 1862 issue of the Police Gazette, which carried his description, is one of the few issues not stored anywhere in national or local archives, so we don’t know what he looked like. But he was able to use his reputation as a Wesleyan preacher to attract supportive networks and capital. Scoria bricks solved a serious problem for iron manufacturers on Teesside, in removing and recycling waste, at a time when urban areas were expanding and building many new roads and houses. 

I was pleased to note that our researches were recently referenced in a 2024 Hull City Council management plan for Hessle Road. So it's an example of how a local history group carrying out relevant research can support urban planning. 

Do you have them in your old neighbourhood?

Bibliography
Major, Susan, ‘Scoria bricks in the back alleys of York’, York Historian, 41 (2024) 38-54.
Morris, Charles, ‘Scoria blocks’, Cleveland Industrial Archaeologist, 13 (1981) 23–32.
Clements Hall Local History Group, is currently mapping the location of these bricks in York, see https://www.clementshallhistorygroup.org.uk/blog/scoria-bricks-do-you-have-them-in-your-neighbourhood.
 

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