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Discussion Starter · #1 ·
Hi All-
I've recently removed the mortar from the inside of an exterior wall in my DC brownstone. The wall is on the end of the end-unit rowhome. After removing the mortar, I discovered the brick was covered in a black tar like substance. I believe this was either used to seal the wall or give the mortar something to stick to.

I'm having trouble finding a way of getting the tar off. My goal is to expose the beautiful brick underneath. This is a lot harder than I originally thought.

Any suggestions? I would like to avoid staining the brick itself. I've tried dry ice, but couldn't keep it on there for long enough to use it. If I could keep it on for long enough, then I could freeze the tar and chip it off. Any ideas for how to keep the ice on there for long enough? I.E. plastic of some sort.

The tar itself is fairly brittle as is and does come off, but its a big wall with a lot of space to cover. I've also though about sandblasting or soda blasting, but that is tough to do given that it is indoors.

Any help is appreciated! Photos below.
 

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You need to know what the constitution of the bricks are before you start on this type of project.

Media blasting might work, but I just wonder about the brick.

Dry ice seems promising if it can chill that tar to a temp where it will flake off with a bit of agitation.
 

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you can have that media blasted pretty easily. once set up, it would take the guy less than an hour to do what is pictured. and it wouldn't damage much of anything.
you would empty the room and seal it off. perhaps thee Blastor would clean up for you, or you would = basicly sweep, vacuum and wipe.
cost, idk. but, if it is less than $1000, and it would probably be a lot less than that. it would be money well spent compared to your other options.
 

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Discussion Starter · #5 ·
Well, I'm back in the game of house remodeling on my home. I'm about to undertake a big addition. I figured I'd better give back what was given to me with all the advice I received on here the last time. Thank you, by the way.

In short, I ended up completing this project by taking an iron scraper to the wall first to get off as much excess tar as possible. Next, I took a good old belt sander with low grit paper and went to work. It's about 200 sq ft of brick wall. It took about 3 months of work on nights and weekends, not consistently. I got very frustrated and exasperated by a lot of the work, so I had to take "mental health" breaks. In short, it turned out quite nicely for my purposes compared to the $10K quote I got to do the work and re-point the brick. I would mention that the contractor told me they used the belt sander method, similar to what I did. Also, my DC rowhouse built in 1913 had this tar covering in order to water proof this wall. My unit is an end-unit and this was common practice I have learned. If I had used the party wall, it would likely not have been covered in tar. I finished the project off with a semi-gloss sealer. The total cost after approximately 250 sanding belts was around $750.


I wouldn't recommend this to anyone, but it's a great way to save a few thousand dollars. DEFINITELY wear a mask.










 

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dry ice works on materials that are usually strong across the whole spectrum,,, problem we found w/this work & ice/walnut shells/white sand is some of the coatings are thinner in 1 spot than another,,, therefore, punching thru the thin work'd fine while thicker obviously longer leading to impact friction hearing up the remaining mtl & causing the **** to spread,,, collateral damage was also deeper holes in the adjoining brickwork,,, we tried diamond grinding, too

certainly the aurands left minor grooving however much more acceptable both aesthetically & financially
 

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While i agree with the walnut/sand causing impact friction, and possibly causing the **** to spread, i doubt that would happen with dry ice at a temp of -109.3 degrees Fahrenheit, no collateral damage to worry about either.
 

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Discussion Starter · #12 ·
I tried dry ice in block form and using a fire extinguisher, followed by a hammer to try and break it off. This did not remove the stain on the brick however. It did help to take off a good portion of it, but no more than a steel scraper and old-fashioned elbow grease.

I think I explored CO2 blasting but the cost was what drove me away from it.
 
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