[Garyl53]

Hi,
I put some mortar in the back of the joints of a red sandstone wall to provide some support for the top row of stone that was sliding all over the place. It rained and now there is a little mortar film on the front of a few of the stones. Water and scrubbbing did not do anything. Is there a cleaner that can be used that will not harm the red sandstone?
Thanks,
Gary

 

[Garyl53]

I was concerned that the acid would discolor the red sandstone. I guess I can try it on a small piece before I try it on the wall.
Any other ideas?