The most effective tip for removing saltpeter and mould from walls

a bottle of muriatic acid
1 brush
containing water and soap Seal for
Bring a mask, gloves and glasses to protect your eyes. Use the metal brush to remove all saltpeter from the surface of the walls.

Mix a glass of hydrochloric acid with three glasses of water and mix them with the brush until they mix perfectly.

Apply the solution with the brush. A foam will form and allow to stand for five minutes. Then rub the wall with soap and water, rinse and clean.

Once the wall is dry again, you can apply cement to fit the wall, followed by a sealant. This step may not be necessary.

Let the concrete dry and then apply a few layers of paint to restore the wall to its original appearance.