Heavy carbon buildup removal / restore limestone

Looking for an expert to help me understand how to clean these. I get RFQs frequently and have not found a chemical that will touch the carbon. I tried heritage restore, sh, etc. Nothing will touch it.

Any ideas?
It’s limestone / sandstone

Highly doubtful that is carbon. Where would it come from? It is a church not a smoke stack. It is mold under the surface of the stone. Search the forum and you will find the answer.

1 Like

It’s over 100 years old in a downtown area and the bricks were re purposed from before that. I have called other contractors in the area and spoken with about 75% of them. Everyone is saying soda blasting and I have called multiple manufacturers of chemicals. Nothing has touched it yet…

What all have you tried? Looks organic so should clean up pretty easy. Might require a few applications.

straight sh, heritiage restore, one restore, tag it graffiti remover

1 Like

Have you tried to scrub it off. I’m assuming you are using hot water

How many applications of sh? Limestone sometimes takes multiple applications without rinsing in between.As mentioned agitation helps too. I just have a hard time believing it’s carbon buildup. I guess you never know though.

@CFH has a couple of really good threads on it somewhere.

We’ve had a couple of long threads about this in past year. Look under historic restoration.

Here is one of them.

When you say straight SH, do you mean with a pump spray or 12v pump?

When I say straight sh I mean 12.5% pump up sprayer on it.

I know you guys are trying to help, but when I say it’s not algae, I mean it. Yes there is some here and there, but that is not what I am talking about. I am talking about heavy mineral / exhaust / carbon, etc build up from the past 100-150 years.

1 Like

Sodium percarbonate, pure.

I dont understand why you dont just use a scrub brush and a ladder. Apply chemical and scrub. Are you trying to find the easy way sometimes in this business you gotta apply some elbow grease oui ts just that simple

Scrubbing will not work. I have not tried hot water yet. I am trying purple power and industrial strength simple green.

Some areas have 1/8th or more think layer of this buildup. It’s common throughout my area. The only thing I have heard that works at this point is soda or sand blasting.

Have not tried hot water yet.