How to Remove Mortar Residue Off of Flagstone
- 1). Scrape off any larger areas of mortar off from the surface of flagstone with the edge of a trowel.
- 2). Brush the mortar with a wire brush to remove any remaining mortar from the surface until you are left with just a thin film of mortar that cannot be removed.
- 3). Apply the acid wash to the surface of the flagstone. Allow it to sit on the surface until the mortar residue appears to be loosened.
- 4). Brush the residue off with a wire brush while the wash is still on the flagstone. Rinse the residue and acid wash off with a water hose until the flagstone surface is completely clean.