Things You'll Need
Chemical cleaning solution
Mortar stains often take the shape of drips and drabs, which are unsightly and uncomfortable to walk over. They're a common problem after the installation of pavers and can ruin the look of your limestone. You don't have to hire someone to get rid of them, however. Removing them isn't a complicated process; it just takes some elbow grease and a few tools. For tough stains, you may require a commercial cleaning solution, which will probably contain an acid. Always follow the manufacturer's directions with such chemicals.
Chisel away as much of the mortar as you can. Use a hammer to tap the chisel and hold the chisel at an angle nearly parallel to the paver. This will help prevent damaging the limestone as you chip away the mortar.
Run clean water over the stones as you chip at them. If you can't find someone to pour water over the work, wet the mortar often to lubricate the chiseling.
Chip the mortar to a thin layer, down to about the thickness of a credit card.
Use a wire brush to scrub the layer of mortar. You may be able to remove most of the residue this way, but for stubborn stains you might need an acid.
Choose a commercial cleaner. These can contain some heavy duty acids, including muriatic (hydrochloric) acid. Such cleaners dissolve a thin layer of the limestone, releasing the mortar.
Test your cleaner on a small, inconspicuous spot before applying it to your paver. Some cleaners can discolor limestone.
Remove remaining mortar with your commercial cleaning solution and a scrub brush. Dilute your cleaner as per the instructions. It's better to have to apply it a second time than to apply too much on the first attempt.
Rinse the area thoroughly with clean water and pour on a little baking soda to ensure that the acid is neutralized.
Dilution of the acid and frequent rinsing with clean water will keep the cleaner from dissolving too deeply into the limestone.
Always wear gloves, a dust mask, old clothes and safety goggles when working with cleaning solutions.