[Markus A]

Hello guys,

Fledging DYI'er here. Happy to be on board. Will post any results back here in case it's helpful to someone else in the future.

I'm repointing an old stone wall that used to be a kitchen firepit in this old farmhouse.

It was going great... until I got to the lower third of the wall. The stone here is covered with some kind of tough layer of sand/soot/old mortar/something and I can't figure out how to expose where the stones are without damaging them in the process.

In the attached photo, I've highlighted the regular area in green and the lower area in red.

I have a power chisel, but if I use it here, I could just be chewing into stone and don't want to damage them.
I have a pressure washer, but this is indoors and well... I don't know how good an idea is.

Could it just be one large stone?

Is there some method of cleaning, some chemical or product I could try to see if I could figure out what I'm dealing with here?

Thanks for any help or insights. I'm stumped with this.

 

[chandler48]

That is one large stone. No joints to point except in the upper left. We can't see the entire unit, but I would be reluctant to repoint this as it seems to be stacked stone and has an elegance all to it's own.

 

[Markus A]

Thanks for the reply, Chandler.

Yeah, it really looks like a single stone. But with a suggestion from someone else, I just discovered a new join. See the image below. Man... there must be an easy way to expose them all so I don't have to just keep chiseling everything until I get lucky and hit a softer spot. The old mortar is baked hard making it SO difficult to tell what's what. Gonna take me forever if I can't find a way.

 

[ClarenceBauer]

Thanks for the reply, Chandler.

Yeah, it really looks like a single stone. But with a suggestion from someone else, I just discovered a new join. See the image below. Man... there must be an easy way to expose them all so I don't have to just keep chiseling everything until I get lucky and hit a softer spot. The old mortar is baked hard making it SO difficult to tell what's what. Gonna take me forever if I can't find a way. View attachment 647649

You can use a Bushing tool (hammer )
You can get these tools in many different cost ranges.
Trow &Holden have some of the very high class tools
You can also get this tool for the SDS hammer-drill.
Also comes as a hand held hammer.
Any of the above will remove the surface coating & not damage the Stone.

 

[ClarenceBauer]

You can use a Bushing tool (hammer )
You can get these tools in many different cost ranges.
Trow &Holden have some of the very high class tools
You can also get this tool for the SDS hammer-drill.
Also comes as a hand held hammer.
Any of the above will remove the surface coating & not damage the Stone.

 

[Markus A]

Thanks, Clarence. I have an SDS hammer drill and I just ordered the part.

Also I wanted to add a description for everyone detailing the layer that covers everything:

Under the black surface, it's like a fine brown/beige powder, darker brown and very dense at the surface with black soot on top, then turning into dryer, looser, beige powdery material the deeper into the wall you get.

 

[ClarenceBauer]

Thanks, Clarence. I have an SDS hammer drill and I just ordered the part.

Also I wanted to add a description for everyone detailing the layer that covers everything:

Under the black surface, it's like a fine brown/beige powder, darker brown and very dense at the surface with black soot on top, then turning into dryer, looser, beige powdery material the deeper into the wall you get.

It sounds like a very soft high Lime content mortar.
If by any chance it dates back before 1910 I would say it is a Lime Sand type mortar.
As for the black ??? dirt , tar or very old paint.