One of the unfortunate problems that can develop on stone buildings is caused by moisture. Rainwater can cause calcium nitrites to leach from the porous stone.
As this solution runs off, it often forms a deposit on the surface of the stone. Although they do not damage the stone, such deposits detract from the appearance of the building. Luckily, they are easily removed. First, the thickest deposits are removed by hammering. Then, a chemical wash releases the remaining residue.
To learn how you can participate in our building restoration and improvement project, visit our page about the Landmark Century Campaign.