Help with old brick cleaning

This is from an 80+ year old building a friend of mine owns. I did some testing and nothing I tried (2500psi, roof wash (sh plus detergent), acid, two-stepping) did much of anything to the grime. I tried some higher pressure (3200psi green tip) and at first I thought it was working but on closer examination i think it altered the texture (ie stripped off some brick). Can anyone identify the brick or more importantly, what will clean it up. The grime is most prominent on the top lip of each brick and I thought it was just an organic stain (mildew) but the sh didn't effect it. Another question...the contractor bidding on tuck pointing it wants the power washing done first, but I'd rather have the tuck pointing done first, is there a best order to have those done?

Here's a couple more photos.

What acid did you use and how did you use it to not get results?

The brick appears to be concrete bricks with a bit of black calcite around the edges. The joints are a bit worn down but can still be cleaned.

Dis you try any bleach or a house wash mix to see if the black was mold? Of it is, then easy fix. If it's calcium then this needs to be treated as a restoration and requires a bit more experience.

Craig said:

What acid did you use and how did you use it to not get results?

The brick appears to be concrete bricks with a bit of black calcite around the edges. The joints are a bit worn down but can still be cleaned.

Dis you try any bleach or a house wash mix to see if the black was mold? Of it is, then easy fix. If it's calcium then this needs to be treated as a restoration and requires a bit more experience.

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I did try bleach (that's what I mean by "sh" and roof wash mix being about 4 x the strength of house wash mix).

For the acid I tested a very dilute "safer muriatic" (I think its a hydroflouric blend but its in the other truck at the moment so I can't check it). I could run back and try some F9 if you think its worth a go.

Would a black calcite bleed out most prominently near the upper portions of each brick? I'm thinking it might be 80 years of dust, atmospheric pollution just baked in there. This wall is north facing so that's why I thought mildew, but I've cleaned mildew off brick lots of times before and this is definitely a different animal. The joints (mortar) I think was and is a redish tint.

F9 won't work here. I would up your strength of the HCL product and apply it a certain way. Call me if you get a chance tomorrow.

The brick is a clay brick and the joints is a scratch joint , have you tried one-restore? If it were me I would try one-restore straight let dwell for about 5 min then rinse. The brick and joints need to be cleaned before the building is tucked so the mason can match the true color of the joints if he does it right it shouldn't get on the brick. You can call me too if you have any questions.

Benchmark said:

The brick is a clay brick and the joints is a scratch joint , have you tried one-restore? If it were me I would try one-restore straight let dwell for about 5 min then rinse. The brick and joints need to be cleaned before the building is tucked so the mason can match the true color of the joints if he does it right it shouldn't get on the brick. You can call me too if you have any questions.

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Clay pavers shouldn't wear down like that from what my experience, could be wrong? I haven't seen aggregates get exposed like that in clay pavers either. Most clay pavers have a life expectancy of 40 to over 100 years or more due to their strength and hardness.

Either way, sometimes of the pavers were not fired and compacted precisely and they can deteriorate more quickly. Or, they were made to mimic other stones and bricks. Some are hard to tell of they are concrete, stone or clay until you hit them with cleaner. Concrete and porous stone will foam with HCL, clay won't (unless it is reacting with surface salts).

I'd follow the advice of Aaron and try the one restore. I think you'll need an HCL product or something recommended by the paver manufacturers. Many will tell you not to use HCL products but in my restoration career they produce the fastest results.. Just use a little product at a time as you'll not want to etch the paver much worse than it is now in order to clean them.

Just re-read your post that these pavers are 80+ years old. This could be a really good thread in paver identification!

Ok. Just got off the phone with Aaron from Benchmark. These are definitely CLAY and not Concrete. The face of the paver has the deteriorated look from the wire mesh used to create it. They are actually in pretty good shape for the age of the paver.

Safe restore may work as well as F9 may work. If the black staining is more of a black pollutant crust, F9 will work better than Safe restore but if it is calcium related the reverse will hold true. Good luck and call Aaron or myself if you need further help.

Thanks so much guys. I'll do some more testing and get back with the findings.

We're wrapping this project up with GSR from eacochem. its working great but some of the anodized aluminum window frames look a little discolored, I assumed we've acid etched them despite keeping them wet throughout. What's the remedy to restore acid burned anodized aluminum?

Thanks

Nice Thread