When water didn't do it for me on a similar project, I did have success with a muriatic (a.k.a. hydrocloric, HCl) acid solution. I don't think ammonia is going to do it - you're basically trying to dissolve calcium and other mineral deposits and I think that an acid is likely to do a better job.

I'd definitely try Randy's suggestions first, but the acid isn't that terrible if you're careful. Try it on a small area first, dilute it, do a small area at a time, wear gloves (nitrile or heavy rubber gloves will hold up better than latex gloves) and goggles, and have good ventilation, with possibly a fan to keep the air flowing. I believe that most masks (even those with the carbon canisters) won't filter the vapors, so good ventilation is a must. Also, if you store the acid, keep it away from other stuff, particularly metal containers. Over time, even a closed container of the acid will leak vapors that will corrode everything around it.

Well, I guess that all sounds a little bad, but it's really not that bad...

I did a similar job about 2 years ago. It was a huge ordeal. After exposing the brick, it became obvious that I also had to tuckpoint the wall. This required grinding out the old mortar (very dusty).

Before I replaced the mortar, I also sandblasted the bricks (also dusty). This removed all of the calcium/plaster deposits that were embedded into the bricks.

After that I tuckpointed the wall with new mortar.

The final step was spraying the wall with a sealer. The stuff I used is commonly used on brick patios to keep the sand within the joints of the brick.

Good luck! Here's a bad pic of me posing in front of the exposed brick wall

file:///Users/howardludwig/Desktop/DSC00548.JPG

Howard Ludwig