As the mixing by hand is a rather slow and tedious method, and the hoe and box method are not very generally known, several machines have been devised to do the work. None of them, however, has given such satisfactory results as to bring it into general use.
One of the machines is called a "jig," or "milk shake" machine,1 and consists of a cup which moves rapidly up and down, this motion being imparted by means of a hand wheel, crank and connecting rod. The dry cement and water being placed in the cup and tightly covered, a few rapid turns of the wheel are sufficient to reduce the cement to a paste. This form is only applicable to neat cement mortars, and has been said to give unsatisfactory results even for these, though in some laboratories this machine has been used for all neat mortars.
Other forms have been made in which the mortar is thoroughly stirred by means of forks or blades projecting into the mortar from a horizontal arm above. The gager devised by Mr. Faija is constructed on this principle, and similar machines may be obtained from manufacturers of testing apparatus.