of Oliver Evans
The hopper-boy, or cooler, was invented in the late 1700's by America's
best known milling engineer and inventor, Oliver Evans. This mechanical
device, once commonly found in the upper floor of mills, is no longer in
use. It faded out of popularity less than 100 years after its invention.
Designed to cool hot flour coming off the buhr stones, the hopper-boy was
automated and more sanitary than the traditional method it replaced. This
was one of the five inventions that were to make Oliver Evans famous to
Our story begins in 1782 when Oliver Evans and his younger brother Joseph
moved from Delaware to Tuckahoe, Maryland. Here they opened a store on the
Eastern Shore. However, his two older brothers in Delaware were planning
to run a mill. Because Oliver Evans had mechanical training and interests,
he was charged by them to design the mill machinery. He began to inspect
local Maryland large and small mills. Prompted by the current inefficient
practices, he began to formulate his ideas for a completely automated flour
mill. His efforts started with paper models of bucket elevators. He went
on to build several devices which together became his new system of automated
After his September 1785 marriage to Sarah Tomlinson, Evans continued work
on his revolutionary ideas and perfected the principle of the hopper-boy.
By September 1785, after nearly two years work, the Evans brothers had invested
in a mill on Red Clay Creek near Newport, Delaware. Their aim was to secretly
revolutionize milling practices utilizing the devices Oliver Evans had labored
so long to perfect.
Bucket elevators, conveyors, drills, descenders, and the hopper-boy were
built for the mill from models that Evans had perfected. The devices were
concealed from the public, and the doors were kept locked while the interior
was completely renovated. These mechanical devices would become the heart
of the American, or flat grinding, system, still used by smaller, custom
mills into the early 20th century.
In the pre-Evans mill, millers or boys would carry freshly ground flour
sacks up ladder like stairways to the top floor or attic of the mill. Sometimes
it was hoisted up using ropes and buckets or sacks, and dumped on the floor
where it was spread with a rake to cool and dry it. The miller's helper
in this process was called the hopper-boy. The flour might remain on the
floor for many hours, filling the loft with flour while waiting for the
moisture to evaporate so it would not sour later. Egg laying insects loved
it! After the flour was dried and cooled, it was bolted, where again it
would be deposited in hoppers or bins to age and whiten. Evans invention
cooled and raked the freshly ground flour mechanically: saving labor, time,
and space; and, it did a better, more complete job.
The hopper-boy was a much more difficult device to invent than the bucket
elevator. Evans would later say, "Both to spread and gather at the
same time then seemed absurd, and the discovery caused months of the most
intensive thinking, for the absurd always presented itself to baffle and
defer me!" In 1795, Evans wrote and published his famous classic, "The
Young Mill-Wright and Miller's Guide" (reprint for sale in
SPOOM's Bookstore) that would be reprinted three times during his lifetime,
and in twelve more reprintings after his death. In his book he describes
how to build his inventions.
Ground wheat from the millstones would fall into a bucket elevator where
it was raised to the hopper-boy on the upper floor. The hopper-boy was customarily
enclosed within a circular or octagonal wall (not found in Evans original
drawings or descriptions) that kept the flour confined. As refinements were
made, these walls became more and more completely enclosing the device,
however, this would defeat its purpose as it needed an exchange of air to
complete its purpose.
The miller's hopper-boy once worked in a room in the loft with a rake. But
Evans hopper-boy would fill the loft with a shallow, circular tub which
contained a revolving rake usually about 12 to 15 feet long. The actual
size would depend on the capacity of the mill. The rake, with arms of soft
poplar, was turned by a cog wheel, and it turned the flour over and over
by the use of paddles. The flour was eventually swept by the device into
a chute that directed it to the bolter below. The size of the rakes actual
varied from 4 to 15 feet long. Smaller machines had one discharge hole to
one bolter, while larger machine had two discharge holes feeding two bolters.
In operation, the rake was attached to a central vertical shaft which effected
the motion about 4 rpm's. To the shaft was attached a horizontal balance
arm; the arm was pinned to the vertical shaft in the center. The rake itself
would float upon the vertical shaft being governed by a counter weight that
was tied with a rope at one end and ran up the vertical shaft through a
pulley in the shaft to the rake at the opposite end. The rake had to be
able to float to adjust to the volume of the flour dumped into the tub.
The counter weight regulated the length of the time flour spent in the hopper-boy.
The rake, always on top of the flour, moved the flour in a declining spiral
to an off-center discharge hole, or holes. The action of the rake's paddles,
or flights, turned the meal over many times before falling to the bolter.
Other of Evans inventions were designed to move material horizontally or
vertically through the mill. These were the elevators, the conveyors, the
drill, and the descender.
The elevator raised material vertically. It was an endless strap of (white)
leather that revolved over two pulleys. To the strap were attached a number
of equidistantly spaced small, wooded or metal cups.
The conveyor was made of maple or smooth hardwood paddles that were attached
to an endless screw and arranged in two continuous spirals. The device was
placed in a wooden trough and was used to transport material horizontal
through the mill.
The drill is similar to the elevator and the conveyor in design. It has
an endless strap, like the elevator, to which are attached blocks of popular
or willow. Moving between two pulleys, the drill moves material horizontally
along the bottom of a wooden case from machine to machine.
The descender was a broad endless strap made of leather like an elevator,
but moved freely over two pulleys with different elevations creating a slight
downward slope. The descender operates by the weight of the material, much
as water falls over a water wheel, rather than by some outside force. The
material moves on top of the belt at a controlled rate, much like an assembly
line conveyor belt.
When Oliver Evans opened his automated mill on Red Clay Creek, it was seen
by 5 Brandywine millers. J. Shiply exclaimed, "It will not do it, cannot
do, it is impossible that it can do!" But he saw it with his own eyes,
and millers of the era who declined to adopt Evans's hopper-boy were doomed
to produce an inferior flour. Evans thought the most of his hopper-boy invention.
He organized a company in Philadelphia which made and sold milling goods;
however, they refrained for whatever reason from putting their name on their
goods. Thus, it is impossible to prove that any Evans produced machinery
In Evans's day, American millers used the old American or flat grinding
system of milling. The fast turning millstones were set close together and
placed a lot of pressure on the grain. They needed to be well dressed to
do their job. The object was to produce as much flour as possible through
one pass through the stones. Grind once, sift once was the rule. The meal
would leave the stones hot and damp; the duller the stones, the hotter would
be the flour. The bran was broken into fine particles, and the middlings
turned into warm clumps which would clog the bolting cloths if not cooled
before bolting. Hence the need for a device (or person) like the "hopper-boy."
The hopper-boy fell out of use with the coming of the high grinding, or
gradual reduction process of milling that was popularized in the 1880's.
In this method, the stones were set farther apart, and naturally produced
a cooler flour. The flour was additionally cooled in the elevators as it
was carried up through the floors in small cups.
An adaption of the hopper-boy is still used in some coffee mills today
to cool freshly roasted coffee beans before they are ground. The adaption
of the hopper-boy or cooling pan is the round red device in front of the
coffee roaster (that is silver with the red hopper) to the left.
Hopper-boys can still be seen today. Remnants are occasionally found
in attics with only the rakes, vertical posts, or tub circle remaining.
The uninitiated do not realize what these devices did. Complete hopper-boys
can be seen today at (1) Klines Mill south of Stephens City,
Virginia. (2) Pierce Mill, Rock Creek Park, in Washington, D. C.
where a hopper-boy from the Boxman Mill, Linesboro, Maryland was removed
and reinstalled in the Pierce Mill by the Fitz Water Wheel Company on the
1930's. (3) Colvin Run Mill, Fairfax, Virginia has a reconstructed
hopper-boy. (4) The Duff Roblins Mill, Black Creek Pioneer Village,
located just north of Toronto, Canada, has a reconstructed hopper-boy. (5)
The Hagley Museum, Wilmington, Delaware, has a working, miniature model
of the hopper-boy in an Oliver Evans Mill model. (6) The Staley Mill,
the oldest mill inOhio, was built in1818, at the Staley Saw Mill Farm in
Miami County. It has a hopper-boy besides other musuem pieces in the mill.
Note: A version of this article by T.R. Hazen appeared in
OLD MILL NEWS, Summer 1995, Vol. XXIV, No. 3, Whole Number 92, pages
8 & 9.
Return to HomePage