Читать книгу Scientific American Supplement, No. 275, April 9, 1881 - Various - Страница 7

The following article was written by Albert Hoppin, editor of the Northwestern Miller, at the request of Special Agent Chas. W. Johnson, and forms a part of his report to the census bureau on the manufacturing industries of Minneapolis.

"The development of the milling industry in this city has been so intimately connected with the growth and prosperity of the city itself, that the steps by which the art of milling has reached its present high state of perfection are worthy of note, especially as Minneapolis may rightly claim the honor of having brought the improvements, which have within the last decade so thoroughly revolutionized the art of making flour, first into public notice, and of having contributed the largest share of capital and inventive skill to their full development. So much is this the case that the cluster of mills around the Falls of St. Anthony is to-day looked upon as the head-center of the milling industry not only of this country, but of the world. An exception to this broad statement may possibly be made in favor of the city of Buda Pest, in Austro-Hungary, from the leading mills in which the millers in this country have obtained many valuable ideas. To the credit of American millers and millwrights it must, however, be said that they have in all cases improved upon the information they have thus obtained.

"To rightly understand the change that has taken place in milling methods during the last ten years, it is necessary to compare the old way with the new, and to observe wherein they differ. From the days of Oliver Evans, the first American mechanic to make any improvement in milling machinery, until 1870, there was, if we may except some grain cleaning or smut machines, no very strongly marked advance in milling machinery or in the methods of manufacturing flour. It is true that the reel covered with finely-woven silk bolting cloth had taken the place of the muslin or woolen covered hand sieve, and that the old granite millstones have given place to the French burr; but these did not affect the essential parts of the modus operandi, although the quality of the product was, no doubt, materially improved. The processes employed in all the mills in the United States ten years ago were identical, or very nearly so, with those in use in the Brandywine Mills in Evans's day. They were very simple, and may be divided into two distinct operations.

"First. Grinding (literally) the wheat.

"Second. Bolting or separating the flour or interior portion of the berry from the outer husk, or bran. It may seem to some a rash assertion, but this primitive way of making flour is still in vogue in over one-half of the mills of the United States. This does not, however, affect the truth of the statement that the greater part of the flour now made in this country is made on an entirely different and vastly-improved system, which has come to be known to the trade as the new process.

"In looking for a reason for the sudden activity and spirit of progress which had its culmination in the new process, the character of the wheat raised in the different sections of the Union must be taken into consideration. Wheat may be divided into two classes, spring and winter, the latter generally being more starchy and easily pulverized, and at the same time having a very tough bran or husk, which does not readily crumble or cut to pieces in the process of grinding. It was with this wheat that the mills of the country had chiefly to do, and the defects of the old system of milling were not then so apparent. With the settlement of Minnesota, and the development of its capacities as a wheat-growing State, a new factor in the milling problem was introduced, which for a time bid fair to ruin every miller who undertook to solve it. The wheat raised in this State was, from the climatic conditions, a spring wheat, hard in structure and having a thin, tender, and friable bran. In milling this wheat, if an attempt was made to grind it as fine as was then customary to grind winter wheat, the bran was ground almost as fine as the flour, and passed as readily through the meshes of the bolting reels or sieves, rendering the flour dark, specky, and altogether unfit to enter the Eastern markets in competition with flour from the winter wheat sections. On the other hand, if the grinding was not so fine as to break up the bran, the interior of the berry being harder to pulverize, was not rendered sufficiently fine, and there remained after the flour was bolted out a large percentage of shorts or middlings, which, while containing the strongest and best flour in the berry, were so full of dirt and impurities as to render them unfit for any further grinding except for the very lowest grade of flour, technically known as 'red dog.' The flour produced from the first grinding was also more or less specky and discolored, and, in everything but strength, inferior to that made from winter wheat, while the 'yield' was so small, or, in other words, the amount of wheat which it took to make a barrel of flour was so large, that milling in Minnesota and other spring wheat sections was anything but profitable.

"The problem which ten years since confronted the millers of this city was how to obtain from the wheat which they had to grind a white, clear flour, and to so increase the yield as to leave some margin for profit. The first step in the solution of this problem was the invention by E. N. La Croix of the machine which has since been called the purifier, which removed the dirt and light impurities from the refuse middlings in the same manner that dust and chaff are removed from wheat by a fanning mill. The middlings thus purified were then reground, and the result was a much whiter and cleaner flour than it had been possible to obtain under the old process of low close grinding. This flour was called 'patent' or 'fancy,' and at once took a high position in the market. The first machine built by La Croix was immediately improved by George T. Smith, and has since then been the subject of numberless variations, changes, and improvements; and over the principles embodied in its construction there has been fought one of the longest and most bitter battles recorded in the annals of patent litigation in this country. The purifier is to-day the most important machine in use in the manufacture of flour in this country, and may with propriety be called the corner-stone of new process milling. The earliest experiments in its use in this country were made in what was then known as the 'big mill' in this city, owned by Washburn, Stephens & Co., and now known as the Washburn Mill B.

"The next step in the development of the new process, also originating in Minneapolis, was the abandonment of the old system of cracking the millstone, and substituting in its stead the use of smooth surfaces on the millstones, thus in a large measure doing away with the abrasion of the bran, and raising the quality of the flour produced at the first grinding. So far as we know, Mr. E. R. Stephens, a Minneapolis miller, then employed in the mill owned by Messrs. Pillsbury, Crocker & Fish, and now a member of the prominent milling firm of Freeman & Stephens, River Falls, Wisconsin, was the first to venture on this innovation. He also first practiced the widening of the furrows in the millstones and increasing their number, thus adding largely to the amount of middlings made at the first grinding, and raising the percentage of patent flour. He was warmly supported by Amasa K. Ostrander, since deceased, the founder and for a number of years the editor of the North-Western Miller, a trade newspaper. The new ideas were for a time vigorously combated by the millers, but their worth was so plain that they were soon adopted, not only in Minneapolis, but by progressive millers throughout the country. The truth was the 'new process' in its entirety, which may be summarized in four steps–first, grinding or, more properly, granulating the berry; second, bolting or separating the 'chop' or meal into first flour, middlings, and bran; third, purifying the middlings, fourth, regrinding and rebolting the middlings to produce the higher grade, or 'patent' flour. This higher grade flour drove the best winter wheat flours out of the Eastern markets, and placed milling in Minnesota upon a firm basis. The development of the 'new process' cannot be claimed by any one man. Hundreds of millers all over the country have contributed to its advance, but the millers of Minneapolis have always taken the lead.

"Within the past two or three years what may be distinctively called the 'new process' has, in the mills of Minneapolis and some few other leading mills in the country, been giving place to a new system, or rather, a refinement of the processes above described. This latest system is known to the trade as the 'gradual reduction' or high-grinding system, as the 'new process' is the medium high-grinding system, and the old way is the low or close grinding system. In using the gradual reduction in making flour the millstones are abandoned, except for finishing some of the inferior grades of flour, and the work is done by means of grooved and plain rollers, made of chilled iron or porcelain. In some cases disks of chilled iron, suitably furrowed, are used, and in others concave mills, consisting of a cylinder running against a concave plate. In Minneapolis the chilled iron rolls take the precedence of all other means.

"The system of gradual reduction is much more complicated than either of those which preceded it; but the results obtained are a marked advance over the 'new process.' The percentage of high-grade flour is increased, several grades of different degrees of excellence being produced, and the yield is also greater from a given quantity of wheat. The system consists in reducing the wheat to flour, not at one operation, as in the old system, nor in two grindings, as in the 'new process,' but in several successive reductions, four, five, or six, as the case may be. The wheat is first passed through a pair of corrugated chilled iron rollers, which merely split it open along the crease of the berry, liberating the dirt which lies in the crease so that it can be removed by bolting. A very small percentage of low-grade flour is also made in this reduction. After passing through what is technically called a 'scalping reel' to remove the dirt and flour, the broken wheat is passed through a second set of corrugated rollers, by which it is further broken up, and then passes through a second separating reel, which removes the flour and middlings. This operation is repeated successively until the flour portion of the berry is entirely removed from the bran, the necessary separation being made after each reduction. The middlings from the several reductions are passed through the purifiers, and, after being purified, are reduced to flour by successive reductions on smooth iron or porcelain rollers. In some cases, as stated above, iron disks and concave mills are substituted for the roller mill, but the operation is substantially the same. One of the principal objects sought to be attained by this high-grinding system is to avoid all abrasion of the bran, another is to take out the dirt in the crease of the berry at the beginning of the process, and still another to thoroughly free the bran from flour, so as to obtain as large a yield as possible. Incidental to the improved methods of milling, as now practiced in this country, is a marked improvement in the cleaning of the grain and preparing it for flouring. The earliest grain-cleaning machine was the 'smutter,' the office of which was to break the smut balls, and scour the outside of the bran to remove any adhering dust, the scouring machine being too harsh in its action, breaking the kernels of wheat, and so scratching and weakening the bran that it broke up readily in the grinding. The scouring process was therefore lessened, and was followed by brush machines, which brushed the dirt, loosened up and left by the scourer, from the berry. Other machines for removing the fuzzy and germ ends of the berry have also been introduced, and everything possible is done to free the grain from extraneous impurities before the process of reduction is commenced. In all the minor details of the mill there has been the same marked change, until the modern merchant mill of to-day no more resembles that of twenty-five years ago than does the modern cotton mill the old-fashioned distaff. The change has extended into the winter wheat sections, and no mill in the United States can hope to hold its place in the markets unless it is provided with the many improvements in machinery and processes which have resulted from the experiments begun in this city only ten years since, and which have made the name of Minneapolis and the products of her many mills famous throughout the world. The relative merits of the flour made by the new process and the old have been warmly discussed, but the general verdict of the great body of consumers is that the patent or new process flour is better in every way for bread making purposes, being clearer, whiter, more evenly granulated, and possessing more strength. Careful chemical analysis has confirmed this. As between winter and spring wheat flours made by the new process and gradual reduction systems, it maybe remarked that the former contain more starch and are whiter in color, while the latter, having more gluten, excel in strength. In milling all varieties of wheat, whether winter or spring, the new processes are in every way superior to the old, and, in aiding their inception and development, the millers of Minneapolis have conferred a lasting benefit on the country.

"Minneapolis, Minn., December 1, 1880."