Hard black substance found behind bump in plastered wall

Cinquestelle

I am preparing a wall for redecoration and in the process chipped away at a bump in the wall about a couple of inches across. I exposed a black rock like substance the size of a coin. This is surely the cause of the swollen plaster. Does anyone know what it is or what it might be and how best to deal with it?

The property is Victorian. The location is about one foot off the floor in a corridor. There are no known appliances or pipes in the vicinity. I have run a detector over the area and metal is not being detected. It does very much look and feel mineral in nature.

Thank you.

Sally_A

Probably a well rusted bolt.

maninthestreet

Sally_A wrote: »

Probably a well rusted bolt.

Not if the metal detector failed to detect it.

Ruski

Its clinker/slag/coal that they used to put in some blocks/bricks. our bumbalow is full of them and they get dug out and filled as and when we decorate.
hth
Russ

Cinquestelle

Thanks Russ. This is new to me. I am googling this now. :T Really, I am hoping I may able to avoid attempting to dig it out as this is bound to lead to creating a much bigger hole. This clinker as you call it is about the diameter and shape of a 50p coin. I wonder how this causes the plaster directly over to blow and whether I may treat it in some way.

Ruski

The nature of the best - just one of those facts that the clinker expands over time and blows the surface of the block. They didn't know that at the time!

Tis really best to dig out and fill - the damage has already been done and it'll probably only pull out when you roller it or whatever.
Couple of layers of pollyfilla to fill the hole back in and then sand back smooth and flat.

HTH
Russ

System

Ruski wrote: »

bumbalow

My imagination is working overtime trying to work out what one of those is

Ruski

!!!!!! wrote: »

My imagination is working overtime trying to work out what one of those is

Its a place where a man with fat fingers lives!