Scoria bricks are a type of blue-grey brick made from slag, originally manufactured from the waste of the steelworks of Teesside, common across the North-East of England.[1] [2] The bricks were also exported around the world and can be found in Canada, West Indies, Netherlands, Belgium, United States, India and South America.[3]
The word Scoria originally comes from Greek, meaning "Excrement", but came to be used by the Romans for a kind of volcanic rock. The bricks were invented by Darlington industrialist Joseph Woodward, in the 1870s, with him registering a patent in 1873 and forming the "Tees Scoriae Company" the same year.[4] At its peak the company was taking 30% of the slag from the South-Tees works.
The bricks were produced by poring the slag caldrons, coming on trains from the steel works, into moulds made with a hinged bottoms and mounted on a revolving platform allowing the moulds to be filled separately. As the bricks solidified they were removed and placed in a beehive oven, where the residual heat annealed the whole of the brick.[5] [6] The bricks were found to be extremely durable against water, frost, chemicals and heavy loads, which lead to them being used as a road surface. On the other hand, an early trial of the bricks in Liverpool found the bricks to wear unevenly and became slippery in wet conditions.[7]