When you undertake a tiling project, it's inevitable that there will be some level of mess. The thinset mortar you use to initially attach tiles to a surface can get into places it shouldn't and end up drying there. This includes smaller smudges or markings on the top of the tiles.
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It's important to try to remove the thinset before you grout and seal tiles, after which it will be far more difficult to remove. There are a few different methods you can try to get the job done. Knowing how to get dried thinset off the top of tiles before grouting can help to ensure that you get the most professional-looking finish possible.
Wash Tiles Thoroughly
If the areas of thinset are rather small and subtle, a good cleaning can do the bulk of the removal work for you. Add a squirt of dish soap or a cup of granulated sugar to a bucket of warm water and then apply it to the areas where thinset is present. Use a sponge to gently scrub the thinset. You may start to notice the marks fading and the thinset coming away from the tiles already.
After you've thoroughly washed the tiled area with soapy water, rinse it clean. Keep any areas where thinset is on top of the tiles damp, as this will make the next stage of the process easier.
Use a Thinset Removal Tool
While the thinset is still damp, you can use a thinset scraping bit. Gently take the tool and apply pressure to one edge of the thinset mark. Then, try to lift and scrape off the thinset. It may take a few passes for you to start to notice the thinset coming off the face of the tile but go slow so as not to damage the tile's surface.
Use Acidic Cleansers
If you're still having difficulty removing surface-level thinset, an acidic cleaning product can help to loosen it and allow it to be wiped away. White vinegar can be a great option, as it tends to be gentle enough not to damage the tile while still effectively removing the thinset.
You can also opt for a grout cleaner that contains cleaning acids. Muriatic acid is a very effective way to remove excess mortar, but care must be taken when using such a harsh cleaning product. When working with this harsh chemical, wear adequate protective gear, including a respirator and gloves. You should also open a window to keep the room well ventilated.
Thoroughly rinse the tiled surface after using any acidic products because any acid residue can weaken the tiles and cause surface damage if it is left on longer than necessary.
Remove Thinset Manually
For really stubborn areas of thinset, you can use a sander to buff the tiled surface. You must be careful when using this method so you do not accidentally cause damage to the surface of the tile. Use 120-grit sandpaper and an orbital sander on the lowest possible setting. Apply minimal pressure to the thinset. Always wear a dust mask when sanding to protect your respiratory system.
Once you've removed the thinset, vacuum the area to remove any dust. You can then polish the tiled surface with a dry rag to make it look as clean and shiny as possible.