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How the Roller Mills Changed the Milling Industry

How the Roller Mills Changed the Milling Industry
Theodore R. Hazen

Milling was founded on sound information and tradition passed on from one generation to another. This is the way it was both in England and when it came to this country. The millstone was the miller's symbol of his art and his industry, and they were reluctant to accept roller mills in place of the millstone. One of the practices that was involved in milling was that metal should never come into contact with ground meal. Grinding grain with something other than stone, was un-heard-of. The millstones were a familiar and trusted device. When roller mills first appeared, the traditional millers never believed that the roller mills could ever replace the millstone as the prime flour milling device.

A natural conflict resulted between the millstone and the roller mill, there was also a conflict between the water wheel and the turbine. Many millers held a belief that the water wheel was superior to the turbine. There were arguments as to which system would work better together, the millstone or roller mill.

When millstone grinding began to be threatened by the roller mills, the miller tried to improve the dressing of the millstone. They tried to increase the number of quarters on the millstone. This they discovered could not make a noticeable improvement over the old style of dressing. They tried to increase the number of furrows but it did not improve the product output. Even with improvements, the millstone still was slower grinding than roller mills.

The roller mill became a good alternative to the progressive millers who wanted a better milling process. They wanted to improve the quality and quantity of their flour product. This led to the primary attraction of the use of roller mills. In replacing the millstone with roller mills, the miller gave up the time consuming process of dressing millstones.

The early roller mills could not do as well of a job in flouring middlings as millstones. It was not until roller mills were improved that their use grew. The first use of roller mills was to break up the grain. Then a pair of millstones would be used to regrind the particles into flour. Eventually this practice became obsolete with the addition of other rollers replacing the millstones. The miller had to learn new skills. He learned that by increasing the number of breaks he could extract almost all the bran and produce superfine white flour.

In the larger milling operations they started to bleach the white flour. It was soon determined that any remaining particles of bran and germ were made more noticeable.

A large-scale milling operation was built as an automatic mill. In these automatic mills there were improvements in the mill's bolters. At this time came the introduction of the purifier and wheat cleaning was greatly improved. Almost every impurity was removed from the grain before it was ground. The germ which effects the shelf life of flour could be scraped off after the first break. The roller mill would break the grain to produce floury middlings. The floury middlings could be bolted and purified to remove some of the bran. Then the middlings would be reground using a slower grinding speed and there would be a more extensive bolting to extract as much flour as possible.

The roller mills increased the amount of flour as well as speed up the milling process. Roller mills could produce more marketable flour than millstone ground operation.

The first (gear driven) roller mills used in Washburn "A" Mill, Minneapolis, Minnesota.

Roller mills used more belt pulley drives with metal shafting and less large gears. The newer roller mills had better roller mountings, using belt drive. These rollers could run faster than the earlier gear operated roller mills. The first noticeable difference was that the belt drive roller mills made considerably less noise. The roller mills had corrugated cast-iron rollers with better bearings and feed control. The differentials, on each roller pair, control the rotation. The non-touching rollers, each ran at a different speed. If both rollers ran at the same speed the grain would travel though with little or no treatment done to it. The slower roller tends to hold the grain while the faster roller shears open the kernel of the grain. This process produces break flour mixed with bran. Increasing the number of breaks and bolts, the total extraction of flour would remain the same as from millstones., The use of gradual reduction with rollers, the percentage of best-grade flours could be increased, while the poor-grade flour would remain the same or be reduced.

The main argument against rollers was the expense of the roller mills themselves. The roller mills became more useful with other gradual reduction equipment being added to the expense such as increasing the number of bolting reels, purifiers and aspirators. Roller milling became more adapted to the larger milling enterprises, the roller mills caused a great demand of capital, which the larger mills could provide to purchase new equipment.

The roller mills are used primarily in the large merchant mill. They were never really identified with the term roller mill. Many of the more successful milling operations converted from millstones to rollers. As the millers installed roller mills, their mills were no longer referred to as grist mills, but they were to be known as roller mills for generations to come. The Leeper Roller Mill, Germania Roller Mills, Juniata Roller Mills are such examples.

Roller mills became identified with the less nutritious whiter flour, while other mills still continued to use millstones to make their stone-ground flour. The nutritional value of the white flour was evident in that so much of the nutritional value was removed from the flour that insects, that infested stone ground flour, could not sustain themselves in the new varieties of the white flour. The insect infestation, which plagued the milling operations was reduced, but it produced a less nutritional flour.

Roller mills in a large merchant flour mill

It was not until the 1940's that the American milling operations started to enrich flour. Flour became enriched with thiamine, niacin, riboflavin and iron. Whole wheat flour does not need to be enriched. Enrichment may have been a great step forward but why was it needed in the first place?

Note: A version of this article by T. R. Hazen appeared in OLD MILL NEWS, January 1980, Vol. VIII, No. 1, Whole Number 30, page 6.

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Copyright 1996 by T. R. Hazen