How to Clean Mortar From Cultured Stone

Lightly tap a chisel into the unwanted mortar with a hammer to form cracks in it. Do this only if you have a lump of mortar on your stone as opposed to a mortar stain. Sand down the mortar until it's about 2 or 3 millimeters thick. Sweep off the dust after you finish.

Open all the windows leading out from the room you work in, if you work in the interior of your home. Always ensure a properly ventilated workplace when working with strong cleaning substances.

Add 1/2 cup of trisodium phosphate to 2 gallons of water and mix well.

Apply the TSP mixture directly on the mortar with a paintbrush. Use just enough of the substance to moisten the mortar.

Scrub the mortar off with a scrubbing brush to remove it. Repeat the application if all the mortar does not come off the first time.