Things You'll Need
Thinset mortar is a construction adhesive used to bond tile to a subsurface -- usually wood. Before it is mixed with water, thinset consists of a dry power; afterward, it has a thick, cement-like consistency. Hardibacker is a cement-based product that provides a level, solid surface on which to lay tile. When laying Hardibacker for new tile, remove any residual thinset beforehand, as it will prevent the Hardibacker from lying flat. Dry thinset may look hard and difficult to remove, but it will come up with minimal effort.
Hold the blade of a tile scraper against the thinset you want to remove.
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Move the scraper back and forth to loosen the thinset.
Sweep up and remove the thinset using a broom and dustpan.
A hammer and chisel will work for small jobs.
Rent an electric scraper for large jobs; home improvement retailers and tool rental shops rent these machines by the hour, half-day, day, week and month.