"Cast" Tiles and Masonry in Bristol

[PatB]

I'm hoping that the broad range and depth of industrial and building knowledge on RMWeb might be able to answer a question that's been puzzling me for quite a while now.

 

Way back, when I was landscaping around Bristol, I noticed that a lot of 19th and possibly early 20th century buildings, walls and garden masonry included things like tiles, wall coping stones and other manufactured "masonry" products made from a dark, shiny material that I initially thought was a variety of brick or similar ceramic. However, examination of broken examples showed an internal structure with lots of swirly flow patterns not unlike solidified lava. IIRC it was also very hard, chewing through cutting discs in my 9" angle-grinder at a phenomenal rate. I speculated at the time that the material may have been cast foundry slag or similar. After all, there must have been an awful lot of it around as an industrial by- product. What better way of disposing of it than to turn it into saleable building materials? I thought that, if it was slag, it might have been brought in from the South Wales steelworks.

 

Anyhow, I wondered if anyone familiar with C19th building materials in the Bristol area might be able to confirm what this stuff actually was.

[great central]

No idea about the actual material but I would doubt it's foundry slag or anything else even remotely metallic. I have a garage I built, slowly, from breeze blocks which must have a small amount of something like slag in. Being some time putting a roof on, the blocks got wet when it rained and rusty water leached out so your buildings would most likely be covered in rust streaks if they were slag based.

[Fat Controller]

Cast slag was used in the Swansea and Llanelly areas for coping stones, blocks for retaining walls, 'rock-armour' for sea-defences. However, this was solid cast slag, not some sort of composite using ground slag and cement. Some came from the steel industry, some was non-ferrous (copper, zinc etc)- all have survived for decades, possibly a century or more, without apparent degradation. 

Foundries produced relatively little slag, as they rely on re-melting pig-iron and steel scrap; in the Bristol area, if the material is local, you're probably looking at zinc slag from 'The Smelter' or iron slag from the Forest of Dean.

The other possibility is that it could be some form of vitrified ceramic, but that doesn't tend to have the structures you describe, and would also probably be too expensive for the uses you described (it's normally used for insulators for overhead lines.)

[Nick Holliday]

Might these items be products of the Cattybrook Brickworks? This was established when the engineer building Patchway Tunnel noticed the quality of the clay being excavated. They produced all the engineering bricks for the Severn Tunnel and many Victorian and Edwardian structures in Bristol. Judging from the photos on the Bristol Museum website the inside looked slightly unusual, and one reference calls them vitreous, implying a slightly different firing technique from normal brick manufacturing, and probably a more shiny finish.

[PatB]

Cast slag was used in the Swansea and Llanelly areas for coping stones, blocks for retaining walls, 'rock-armour' for sea-defences. However, this was solid cast slag, not some sort of composite using ground slag and cement. Some came from the steel industry, some was non-ferrous (copper, zinc etc)- all have survived for decades, possibly a century or more, without apparent degradation. 

Foundries produced relatively little slag, as they rely on re-melting pig-iron and steel scrap; in the Bristol area, if the material is local, you're probably looking at zinc slag from 'The Smelter' or iron slag from the Forest of Dean.

 

 

That sounds like it, or something closely related, might be the stuff.

 

Might these items be products of the Cattybrook Brickworks? This was established when the engineer building Patchway Tunnel noticed the quality of the clay being excavated. They produced all the engineering bricks for the Severn Tunnel and many Victorian and Edwardian structures in Bristol. Judging from the photos on the Bristol Museum website the inside looked slightly unusual, and one reference calls them vitreous, implying a slightly different firing technique from normal brick manufacturing, and probably a more shiny finish.

 

A quick Google for Cattybrook bricks suggests that this isn't the origin. All the Cattybrook images I can find indicate a yellow or reddish shade. The material I'm thinking of was very dark, almost black, but with (usually) a purpleish tinge. I initially thought it might be an engineering "blue" brick material but the swirly internal structure was unlike any clay brick I've seen and suggested that the material had gone into the mould as a viscous liquid, rather than the more usual brickmaking technique of pressing a soft solid into the mould cavity.

 

If it helps, the most common uses that I came across were coping stones with a profile like a tall isosceles triangle with the point rounded off (very common on the stone walls in the areas north of Clifton Downs), and a sort of path-edging tile. That is, a tile with a plain "blade" to bury in the ground and a decorative top edge (scallops and rope twists seemed most common) to form a decorative edge to a path or lawn.

[Andy Kirkham]

There was once a thriving brass industry in the Bristol area, and I've I've always understood that this distinctive material is indeed a by-product of that industry.

 

The remarkable Black Castle at Arnos Court https://www.flickr.com/photos/brizzlebornandbred/2054719812 - now a pub - is made of the stuff.

[DaveF]

 

If it helps, the most common uses that I came across were coping stones with a profile like a tall isosceles triangle with the point rounded off (very common on the stone walls in the areas north of Clifton Downs), and a sort of path-edging tile. That is, a tile with a plain "blade" to bury in the ground and a decorative top edge (scallops and rope twists seemed most common) to form a decorative edge to a path or lawn.

 

The path edging tiles I was familiar in the East Midlands were often a form of terracotta and very hard indeed.  Rather like terracotta floor tiles.

 

There is quite a lot about terracotta on the web.

 

 

 

David

[PatB]

A search on cast copper slag turned up this. The photo of the coping stones on Compton Dando churchyard wall shows exactly the stones I'm thinking of so I think we have a winner. 

[Andy Kirkham]

And here is confirmation https://www.gracesguide.co.uk/Copper_Slag_Blocks

 

[Edit] I see you got there a minute before me, Pat

Edited September 10, 2018 by Andy Kirkham