I’m cleaning a stone house, Lueders limestone, and parts of the limestone are house in color. Particularly around the bottom of the home but also on the front of the home where I had to use straight bleach to remove the black algae.
What is the solution to return the stone to its white appearance?
One of the pictures shows the white appearance of the stone as I want it.
Straight bleach will degrade limestone quickly and the salt can have a reaction that will turn certain areas that color. To my knowledge their is no way to reverse it. You can try OX but it may make it worse. Might want to call a local natural stone company and see what the best route is.
Can also be a combo of where the black algae has eroded the surface of the limestone and reveled the coloring beyond the surface… Just saying I may go that route with the customer if that’s the worst of the damage.
Sheesh. Wish you guys would ask questions before you did stuff.
First you need to pre-wet. Can clean with bleach with some sodium hydroxide. Need a strong alkaline mix, would have mixed something like EBC with it for surfactant.
Second rinse thoroughly with warm water between 150-180 deg. You want medium pressure , no more than 1000psi.
While it’s still wet need to apply neutralizer to keep the orange stains from coming out. Combination of acetic and citric acid. You could probably go 1/2 oxalic and 1/2 citric. Let dwell just a few min and rinse thoroughly again with medium pressure.
So, to try to fix, I’d re-wet completely and then try the acid mix.
Prosoco makes some good stuff for Limestone or as someone mentioned could use One Restore in the future. Could try some on the orange part, but would try the acid first.
Other than using warm water exactly like you restore a fence or deck from a process standpoint. Actually six steps, LOL. You pre-wet, apply solution to clean it, rinse it, neutralize it, rinse it, collect the check