Removing mortar depends on where it is and how stubborn it’s become. Fresh mortar wipes away with a damp sponge, but once it cures, you’ll need mechanical tools, chemical solutions, or both. The right approach varies based on whether you’re grinding out old mortar from brick joints, scraping thinset off tiles, or cleaning mortar smears from a finished surface.
Grinding Mortar From Brick Joints
When mortar between bricks has cracked, crumbled, or deteriorated, the standard fix is repointing: grinding out the old mortar and packing in new. The fastest way to do this is with a 4.5-inch angle grinder fitted with a diamond tuckpointing blade. These blades are roughly 1/4 inch thick overall, with a cutting width of about 5.5 mm, which fits neatly into a standard mortar joint without chewing into the surrounding brick.
Start slow as the blade enters the joint, then increase speed and move steadily along once you’ve reached your target depth (typically 3/4 inch to 1 inch deep for a solid repoint). Most tuckpointing blades are rated up to 13,300 RPM, but you don’t need to run at full speed. Let the diamond edge do the cutting rather than forcing the grinder forward. After grinding, use a cold chisel and hammer to knock out any remaining chunks, then brush the joint clean before applying new mortar.
For smaller jobs or where precision matters more than speed, a manual approach works fine. Score the mortar with a cold chisel angled into the joint and tap with a mason’s hammer, working in short sections. This takes significantly longer but gives you more control, especially on older brick that chips easily.
Silica Dust Is the Biggest Safety Risk
Mortar contains silica, and grinding it creates fine dust that causes permanent lung damage with repeated exposure. Federal workplace safety standards require grinders used for mortar removal to be equipped with a dust shroud and a dust collection system pulling at least 25 cubic feet of airflow per minute per inch of wheel diameter. The collector needs a filter rated at 99% efficiency or higher.
Even with dust collection, you need respiratory protection. For work lasting four hours or less, a fitted N95 respirator meets the minimum standard. Beyond four hours, you need a higher-rated respirator. Safety glasses or goggles, hearing protection, and heavy work gloves round out the basics. Never dry-sweep mortar dust afterward. Use a HEPA-filtered vacuum or wet sweeping instead.
Removing Thinset Mortar From Tiles
If you’re pulling up old tile flooring or salvaging tiles for reuse, dried thinset on the tile surface is the main obstacle. The approach depends on how much buildup you’re dealing with.
For light residue, warm water with dish soap and a soft scrub pad is often enough. Soak the area, let it sit for a few minutes, then scrub. A 1:1 vinegar and water solution in a spray bottle works well for slightly tougher spots. Spray it on, let it dwell, and wipe with a sponge, concentrating on the thinset patches.
For thicker buildup, start by chipping away the bulk with a plastic chisel or a razor blade scraper held at a shallow angle. Metal chisels will scratch ceramic and porcelain, so stick with plastic whenever possible. Once you’ve knocked down the high spots, switch to the soapy water or vinegar solution to clean the remaining film. Vacuum the area when you’re done to pick up fine grit.
Cleaning Mortar Smears From Brick or Stone
Mortar smears on a finished brick or stone surface, the kind left behind after a sloppy pointing job, respond well to diluted muriatic acid (hydrochloric acid). The standard dilution for heavy mortar smears is 10 parts water to 1 part acid, which produces roughly a 3% hydrochloric acid concentration. For light haze or efflorescence, a weaker 20:1 ratio (about 1.5% concentration) is sufficient.
Always add acid to water, never the reverse. Mix the solution in a heavy-duty plastic (HDPE) bucket. Before applying the acid, thoroughly prewet the masonry surface with plain water. This prevents the brick from absorbing acid deep into its pores, which can cause discoloration or spalling. Apply the acid solution, let it dwell for 3 to 8 minutes depending on the severity of the buildup, then scrub with a stiff nylon brush and rinse thoroughly with plenty of water.
Muriatic acid produces hydrogen chloride fumes that irritate your lungs and eyes, and the liquid burns skin on contact. Wear rubber or neoprene gloves, a rubber apron, and splash-proof eye protection. Work outdoors or in a well-ventilated space. Keep a hose running nearby for immediate rinsing if you splash yourself.
Non-Acid Alternatives
If you’d rather avoid acid altogether, non-acidic mortar dissolvers exist. Most commercial formulations use sulfoxide-based solvents that break down cement without producing toxic fumes. You apply them to the stained surface, wait a couple of minutes, then scrub and rinse. The tradeoff is that these products lose effectiveness quickly when exposed to air. The active solvent absorbs moisture from the atmosphere and can become completely inert in under 30 minutes if left uncapped or spread too thin. Work in small sections and keep the container sealed between applications.
Removing Mortar From Salvaged Tiles
Reclaiming tiles from a demolition means dealing with thick layers of old thinset bonded to the back of each tile. Soaking is the most effective approach here. Mix a diluted muriatic acid solution (10:1 water to acid) in a plastic bucket and submerge the tiles. Let them soak until the mortar softens noticeably, typically 15 to 30 minutes depending on thickness. Pull the tiles out, scrub the backs with a stiff brush to remove loosened residue, and rinse with clean water.
This method works well for large batches but requires careful handling. Wear rubber gloves the entire time and work in a ventilated area. Dispose of the spent acid solution according to your local waste regulations, as it shouldn’t go down a storm drain.
Choosing the Right Method
- Old mortar in brick joints (repointing): Angle grinder with a diamond tuckpointing blade for speed, or cold chisel and hammer for control. Always use dust collection and respiratory protection.
- Light mortar haze on surfaces: Warm soapy water or a 1:1 vinegar solution with a sponge or soft scrub pad.
- Heavy mortar smears on brick or stone: Muriatic acid at a 10:1 dilution, applied after prewetting the surface. Rinse thoroughly after 3 to 8 minutes.
- Thinset on tile faces: Plastic chisel for bulk removal, then soapy water or vinegar for the residue. Avoid metal scrapers on glazed surfaces.
- Thick mortar on salvaged tiles: Soak in diluted muriatic acid, then scrub with a stiff brush.
Fresh mortar is always easier to remove than cured mortar. If you’re in the middle of a project and notice smears or drips, wiping them off immediately with a damp rag saves hours of scraping and chemical treatment later.