When I think about mixing mortars and grouts, I am reminded of my friend’s first encounter with the tile trade. As a “green” helper, Gerald was instructed to quickly mix the thinset for the installers. His equipment consisted of a well-worn five gallon bucket and a mixing paddle or should I say, broomstick. That’s right; his normal mixing process included the handle of an old broom. It is difficult to imagine how effective the mixing action was, let alone the aching muscles that went along with this exercise. The tools available today certainly have made mixing mortars and grouts easier and better.
The person mixing mortars and grouts should always follow the manufacturer’s guidelines which include the speed of the mixing motor—normally about 300 rpm. Speeds lower than 300 can lead to ineffective and incomplete mixing while speeds above this recommendation can whip (entrain) air into the mix. This additional air is excessive, making the mortar or grout light and fluffy. While this does ease the fatigue of the installer’s arm, it also significantly reduces the product’s strength. The loss of strength can cause the thinset mortar to not adequately bond to the tile, or cause soft and powdery grout.