The grainer or Michigan process is, like the “kettle method,” a purely American invention, and consists in passing live or exhaust steam through a set of iron pipes immersed in long, shallow wooden or iron vats. These vats rest on a strong wooden frame. They are from 100 to 150 ft. long, usually 12 ft. wide, and from 20 to 24 in. deep; provided with four or six steam pipes having a diameter of 4 to 5 in., and hung on pendants 4 to 6 in. above the bottom of the vats. These pipes are within a few feet of the same length as the grainer, and so arranged that the salt can be conveniently removed towards the outer side of the grainer. To obtain the best effect in a grainer system, the temperature of the heated brine is kept at or near the boiling-point when no lifting or removal of salt is in progress. To do this an abundance of high-pressure steam must first be supplied to the grainers, and, secondly, the constant supply of brine required for the grainers while evaporation is going on, must enter at a temperature but little lower than that of the brine in the grainer. For this purpose two large tanks, called settlers, are employed, which are usually as long and wide as the grainers, but 6 ft. deep, and provided with four rows of steam pipes about 1 ft. above the floor to heat the cold brine drawn into them from the outside cisterns as required. Although the six rows of steam pipes in the grainer have an entire length of from 550 to 750 ft. (suspended in the brine 4 to 6 in. above the bottom of the grainer and with 8 to 10 in. of brine above them) and a heating surface of from 700 to 1,000 square feet, a great deal of the steam supplied to them is not condensed, and, therefore, passes from the grainer pipes into the settler pipes (sometimes passing through a steam trap to separate the condensed water) to heat the brine of the settlers. The main difficulty with which the manufacturers of New York State have to contend is the calcium sulphate. In fact, it is this impurity which causes the interruption of the process, and the laborious cleaning out, whether the kettle, the pan, the grainer, or the vacuum pan is used. It not only entails a great loss of heat in consequence of its slow conductivity, but it also causes the overheating of the metal exposed to direct fire, wherever this is employed. Suggestions and experiments have been made to overcome this difficulty, involving the expenditure of great sums of money, but without any practical results as far as mechanical means are concerned.