Cleaning mortar residue

[Terry Coombs]

It seems that no matter how careful I am , I manage to get some mortar on the face of the stone I'm putting up behind my wood stove . In the past I've used vinegar to cut the haze left on ceramic tile from grouting , but vinegar isn't doing that well on the stonework . I've seen muriatic acid used to clean up bricks , and wondered if it'll work as well on what I'm doing . I know rubber gloves and really good ventilation are going to be necessary , probably wouldn't hurt to wear a rubber/plastic apron in case I splash . How long does the mortar need to set up before I can wash it without cutting the mortar between the rocks ? I assume mixing directions will be on the package .

[nestork]

I'd leave it on for a few hours, and then take MOST of the mortar off the stones with the kind of brush used to clean dentures or any other stiff nylon bristle brush. (Denture brushes have very much stiffer bristles than tooth brushes, which is what you need for that job.)

Brick mortar takes a while to harden, and while it's hardening, you can remove it relatively easily with a stiff bristle brush, paint scraper, putty knife or whatever. For the first day or two, your brick mortar will be easy to remove by mechanical methods.

You can always removed hardened mortar with muriatic acid, but I'd dilute the acid with water. Always pour acid into water, never the other way around. Make your acid solution stronger by adding acid until it removes the hardened mortar easily.

Many new construction materials (like brick mortar, fresh plaster or concrete) have hydrated lime in them that makes them highly alkaline when they're new. Over a year or two that lime reacts with the CO2 in the air to form limestone (calcium carbonate), but within the first one or two years, highly alkaline materials like that will dissolve much more readily in acid than a much more stable material like rock or brick.

But, within the first few hours, you'll find you can pretty well remove brick mortar just by rubbing it with your finger. And, within the first few days, a wire brush will take it off quick and easy.

[Terry Coombs]

I waited after I laid up a section until the mortar was set up enough that the stone didn't move if you pushed lightly , then cut it back between the rocks . I then brushed it smooth with a stiff brush , so it already has the finish I wanted . I just need to remove the "haze" left on the edges and edge of the face . I'm letting each section dry about 24 hours before I lay another course on top of it - I don't want to do this twice . Brick ties are about every foot or so , screwed to the studs . I think it's looking pretty good , just wish I could convince my wife that 1/4" mortar joints in stone work ain't gonna happen ...

[Terry Coombs]

Sounds like I might need to get some of that acid . I figured it would need to be rinsed after application , I've got a sponge I use(d) for tile work that I can use .

[HerHusband]

I just finished building a mortared stone retaining wall, using standard mortar mix I picked up at Home Depot.

I picked up a bottle of muriatic acid at Home Depot (in the paint department), and mixed it about 50/50 with water in a spray bottle. I sprayed it on, let it sit for 3 to 5 minutes until it stopped reacting with the mortar, then hosed the residue. It worked great for me, but I'm not sure how you would handle this indoors. Maybe a spray bottle with water and sponges to clean up the run off?

Oh, and my mortar varied from 24 hours to a few weeks old and it worked fine on both situations.

Good luck!

Anthony

[Terry Coombs]

Thanks ! Turns out the situation isn't as bad as the floor was . I've apparently been getting most of it off as I brush finish the joints aafter I cut them down belowe the rock face . I'll still need to do some cleanup , but not as much as I'd feared .