MILLING-MACHINERY, GRAIN. A very advanced step has been taken in the last twelve years by the introduction of rolls for grinding grain. This has led to a radical change of systems of milling. The old process of low-grinding in which the wheat was reduced to flour by buhr-stones at one operation, and the more advanced new-process" system, have both given way to the Hungarian or high-grinding system, in which the production and treatment of middlings are the essential features, as also the production of as little flour at the early operations in the wheat as possible. The present systems of milling have for their object the separation of the bran from the flour-producing portions of the wheat-berry by gradual reduetion, using chilled iron and porcelain rolls in place of buhr-stones.
The rolls have proved a powerful factor in the radical change of systems, though the purifier must receive proper recognition of its importance as a milling appliance, while the various improved sifting and cleaning devices growing out of the employment of the high grinding system all contribute to make the latter pre-eminent as a method of producing a quality of flour fitted to meet the exacting demands of the day, and to do this profitably commercially, It is well to note that the so-called " new-process " system, used in America prior to the introduction of rolls, may be considered a process intermediate between low-milling and the Hungarian system of high-milling. It no doubt had great influence in preparing the way for the introduction of rolls, and hastened the development of the purifier, especially in America.
It is stated that rolls were used as early as 1820, but it was twenty years later before they attracted much attention. The noted Pesth mill was the first to use rolls alone for the reduction of wheat. For over forty years, previous to the general change from stones to rolls, this famous mill had been in prosperous eonditirm ; and, while it stood as a prominent illustra tion of what rolls could do, millers generally were not inclined to the idea that the system there Used could be advantageously employed on any other than the hard wheats used in that locality. Experiment and enterprise have, however, brought about the almost universal use
of rolls for the various reductions, and the corresponding abandonment of the millstone. The introduction of rolls gave rise to the more scientific phase of milling. With a more general knowledge of the physical structure of the wheat-berry came a better under standing of what was necessary to be done to properly separate the bran and germ from the flour-producing portions. The system of low-grinding made the elimination of these portions impossible, since the fine, brainly particles became inseparably mixed with the flour, as did also the crease-dirt held in the wheat-berry. The Anst1•o-11mmgarisW or high-grinding system provides for their separation at early stages of reduction, thus making it possible to produce a clear, sharp flour. Gradual reduction, where buhr-stones are used, is attended with the same trouble as low-grinding. though in a far less degree. The fine branny particles and some crease-dirt become mixed with the flour, due to the more or less tearing action of the surface of the stone on the bran, especially with hard wheats, and subsequent treatment by reel and purifier fails to remove them. With proper treatment of the wheat by rolls the fine, branny particles and so objectionable when obtained in the early stages of reduction, are almost if not wholly avoided, the middlings obtained are clean and sharp, the bran large and flaky. and the flour preserving the natural sweetness of the grain. A great impetus was given to roller-milling by the introduction, in 1874, of the Wegmann roller-mill, in which rolls of porcelain were used. These mills were introduced into England in the fall of 1876, and into the United States the spring of the following year, by Mr. Oscar of Augsburg, Bavaria.