This section is from "Scientific American Supplement Volumes 275, 286, 288, 299, 303, 312, 315, 324, 344 and 358". Also available from Amazon: Scientific American Reference Book.
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.