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New Process Milling of 1850-70

The Grist Mill at Keremeos, Keremeos, British Columbia, Canada,
practicing their form of "new process" milling.

New Process Milling of 1850-70
by Theodore R. Hazen

This is probably one of the most misunderstood of all milling process, even more so, than the operation of a roller mill. The reason that the "American" or "flat grinding process" was also called "low milling" was that the upper runner stone was set low or close to the bottom bed stone during milling. In "new process" milling the runner stone is set "half as much higher" above the bed stone as compared to low milling. Thus it was also known as "half-high milling." The roller milling process was known as "high milling" or "gradual reduction" milling because the runner stone would be set even higher.

In low milling the idea is to avoid producing as much middlings as possible because as much flour was to be produced as possible in a single grind. Middlings is a material that was considered a waste product along with the bran. The second idea of low milling was to avoid regrinding material at all costs. With the conventional milling setups, regrinding of all ready ground material presented problems with feeding it into the millstones, and created heat generated problems. So then with new process milling the idea was to create as much middlings as possible because this is where the bulk of the flour was produced from. The middlings are ground on separate stones called "middling stones" or "middling pony," and the material is then bolted on separate reels. The flour produced from this process was known as "patent flour" because it was produced from a "patented" process. When the "patent flour" was run in with the "bakers" or "clear flour" (the flour made produced from the first grind of the wheat) the resulting mix or blend was called "straight flour."

During the latter stage of the "new process" milling era smooth germ iron rollers were introduced and they used tailings stock to increase the yield. Many mills also began the process of regrinding the bran on a pair of small millstones just to touch it, not cutting it and leaving it as a broad flake. The bran stones were then gradually replaced by another pair of smooth iron rollers but by that time the rollers had begun to replace the millstone entirely.

Every miller wanted to produce "patent flour," and as much of it as possible because it was advertised as being produced from a "patented" process. Perhaps because of the psychological effect to get anything "patented" it had to be applied for, and granted by the federal government. Because of this "patent flour" commanded almost a double price that the old "bakers" or "clear flour." The new spring wheat over shadowed and took the lead above the best winter wheat made under the old process of milling. The "new process" spring wheat mills were mainly in the central plans of the United States and Canada, while the old soft winter wheat mills were in the eastern part of the United States. By the time many eastern mills begin to adopt the "new process" milling soon after that the milling process changed once again. Some mills used their original ending millstones as middling stones. Ending stones were a smaller diameter pair of millstones that were originally used to preclean wheat if they still remained in place. The mills that installed the smaller middlings millstones some times installed them on an upper floor level than the traditional millstones. One reason was that they were smaller and lighter, and could be located more easily on an upper level. They were often belt driven like the old smut machines and mounted on a waist high platform to make them easier to dress. Another reason goes back to one of the original concepts of Oliver Evans that was to stack the machinery above each other on different levels. Some millers tried to regrind the middlings on the same stone that ground it the first time. The second and third regrinds meant that the stones could not be set higher and had to be set closer and closer. This is where the heat generated problems occurred. Heat can burn up the gluten in the flour and destroy the flour's ability to rise and make good bread. Oliver Evans suggested mixing whole wheat kernels with the middlings for regrinding but this only produced a "bastardized" patent flour in some miller's opinion.

The problem with higher grinding of middlings from the first grind, it did improve the flour made in the first grinding of the wheat, but there was a limit to higher grinding of the middlings to improve the later grindings, and less flour was made in the process. It was also impossible to make the desired quantity and quantity of flour with the old style of millstone dress with the large amount of grinding surfaces known as "land." This was prevalent in the old style of flat grinding. With the old system the miller wanted flour and not middlings so the millstones had a larger proportion of "lands" than furrows. So then in "new process" milling there is a higher percentage of furrows than lands. The lands were reduced and the amount of furrows increased. The grain is dropped below the surface of the land and when it is swept up a feather edge to the surface it is actually sheered by two passing feather edges or passing lands.

It was also found that the capacity of feed practiced in the old system had to be cut down and often the feed system of the damsel and shoe changed completely. Instead of the traditional rap-rap of the song of the damsel that filled the mill with its centuries old song, a silent feed system was developed. The damsel rather than having flutes on the upper end, the once fluted portion became an auger that drawled down the middlings from the hopper or chop box down into the eye of the millstones. It became a force feed system.

The speed of the millstones was also reduced. In the old practice of milling, the idea was to run the millstones close together, with as much feed and speed as possible. Thus a lot of pressure was applied upon the grain and it produced a lot of hot damp meal. With the new process of milling the products were cool and slow grinding became the "order of the day." Besides the differences in how the grain was milled in the old and new process, the care of the millstones, gradually some of the milling machinery became obsolete. It was the one machine that Oliver Evans was the most proudest of that was the one that disappeared, the hopper-boy. Gradually it became evident that the hopper-boy was no longer needed because the grindings and the chop was now cooler. It was soon discovered that spreading it out the ground material in the elevator cups in small amounts, and running in along in chutes and conveyors was sufficient enough to cool it. Generally most people don't understand why the hopper-boy fell out of favor. Many people over the years have apologized to me that their mill does not have a hopper-boy as if it was something that was lost or misplaced over the years. The hopper-boy disappeared not because of its inherent problem with the possibility of material falling into the flour and contaminating it. Millers did try and enclose it the revolving rake in a round walled enclosure, but they discovered that in doing that, it destroyed its cooling effect. The hopper-boy needed to be out in the center of the room mixing with fresh air. The main reason that the hopper-boy became no longer needed, was that the milling processes and methods changed.

Millstone dressing also became more of a science than a one time art. The lightest of dressing and cracking was now sufficient in new process milling. Some millers claimed that millstones the French millstones without any dressing would grind the grain sufficiently just by use of the porous openings. Improvements in driving irons, balancing and truing the stones became more important. Various styles of dress was worked out that could produce more middlings that ever before. The miller spent his time, energy and resources to produce middlings as large, round and clean as possible. This was done at a time when there were no guidelines to follow, or text books written at the time that were available the miller to learn from. This perhaps added to the sense of mystery that some how the process by which it was produced was "patented" through the federal government. It a government secret between them and the miller. Basically the millers had to think for themselves. Some times they would try one thing and if that did not work then they tried another possibility. It became a perquisite that the miller now learned to dress and care for the millstones himself. It larger merchant mills they had crews of men who did nothing but dress millstones.

An important machine that came in to later use during this era was the middlings purifier. The purifier separated the middlings with the use of air currents thus separating the bran from the floury particles bonded to bran, known as middlings. A mediocre grade of flour. View by some to be fit only for the common or lower classes. The first middlings purifier was introduced into America by Edmund N. LaCroix from France in 1871. It was first used at the Washburn Mill in Minneapolis. New process mills that used smooth germ rollers operated from 1875 to 1883. After that the new process milling gradually went out of use because of the complete adoption of roller mills to replace the millstones. Why did this not happen over night? One reason was that the originally the Hungarian roller milling system that was brought to America, it was not automatic. It was like a the system of flour milling before Oliver Evans. Nothing was automatic, and each pair of rolls was a separate machine. Material was introduced into each pair of rollers as if it was being poured into a millstone hopper by hand. Then it was gathered up and carried to the next step or process by hand. At first the mills installed corrugated rolls to break the wheat and retained the millings stones, and used smooth iron, porcelain or both on the second middlings and tailings. Even French millstone material was made into rollers for use in new process milling. Gradually the rollers displace the millstones and in this time the roller system became automated fully.

A concept drawing of an early roller mill that was not automated like that of an Oliver Evans mill.

Buhr Stone Mill: This is the type of mill that was displaced by the roller mill. Generally it was not the Oliver Evans mill that was displaced by the roller milling system but the buhr stone mill that used new process milling. The size and capacity changed from the old flat grinding system to that of the "new process." The drawing does not show grain storage bins, flour chests, packers, or feed or offal bins. The machinery represented shows machinery mainly involved in the milling system of the buhr stone mill. This illustration is figure 13, page 25 of "Practical Milling," by Prof. B. W. Dedrick, National Miller, Chicago, Illinois, 1924.

Figure 13 An Old Buhr Stone Mill.

The one odd thing about Prof. B. W. Dedrick drawings is that he had the silent feed systems on the wheat stones and a conventional feed on the middlings stones. It should be the direct opposite the wheat stones should have the conventional feed and the middling stones should have the silent feed. The silent feed system is shown on the previous page. The following is a list of the parts of the mill in the order of the milling process:

H. Hopper.
D. Dump bin.
1. Elevator one.
R.S. Receiving separator.
W.C. Wheat conveyor.
2. Short elevator.
M.S. Milling separator.
S. Scourer.
W.G. Wheat garner.
D.R. Dust room.
W.S. Wheat stones.
M.S. Middling stones.
M. Main shaft.
U. Upright or vertical shaft.
J. Lay shaft on mill's second floor.
S.K. Sink in front of the millstones.
M.C. Meal conveyor.
4. Flour elevator.
B1. Bolting chest.
5. Middlings elevator.
P. Purifier.
6. Purified middlings elevator.
M.B. Middlings bin.
M.S. Middlings stones.
7. Ground middlings elevator.
B2. Bolting chest.
8. Tailings from middlings reels elevator.
B3. Meal bolting chest.
F.C. conveyor.
9. Flour elevator.
V. Vertical spout is a suction spout used to ventilate the millstones.
L. Lever used to adjust the top runner stone.
r. Rod used to adjust the millstones.
L.S. Hand wheel or screw.

The wheat stones are 48 inches in diameter and the middlings stones are 36 inches in diameter. The wheat millstones still operate at about 125 revolutions per minute but the middling millstones run about 200 revolutions per minute. The bolters operate 25 to 30 revolutions per minute. The elevators operate 40 to 45 revolutions per minute. The conveyor operates about 60 revolutions per minute. Such a mill is capable of turning out 80 to 100 barrels of flour in 24 hours. One barrel of flour contains 196 pounds or 14 stone. In 100 pounds of wheat there is about 72 percent of its total is white flour. In a larger mill, it was the custom to have one or two extra pairs of millstones to use in place of the ones taken up for millstone dressing. Oliver Evans reels were 18 to 20 feet long. New process milling the reels became shorter and were 8 to 12 feet long. Towards the end of new process milling cockle machines and bran dusters came into usage. Diagonal elevators as in 1 an 9 were used only to discharge material on the opposite side of the top floor thus acting as both an elevator and conveyor. Vertical elevators were much easier to layout and install in mills than the diagonal ones. Vertical elevators have to be operating at the proper speed for material to be discharged at the top, while diagonal elevators can be operating at any speed for material to be always discharged. Vertical elevators if not operating at the correct speed the material will fall down the "down" leg and in time clog up the system.

Before they became convetered to all roller mills,
a large merchant millstone mill of Minneapolis, Minnesota.

Typical layout of a stone flour mill of 1878 from the Northwestern Miller (September 7, 1894).
The basement contains the drive equipment, the first flour has mill stones,
the middle floors have purifiers and bolters, and the top floor has dust collectors.

To be Continued

Some other Interior Views of Mills Circa 1850-70

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Copyright 2001 by T.R. Hazen.