EXPERIMENTAL MILLING AND BAKING. 13 
gives the operator a better opportunity to vary his method of grind- 
ing and bolting to suit the character and condition of the individual 
sample. Furthermore, it decreases the possibility of losing material 
or of contaminating one sample with another because of the fewer 
number of places in which material may lodge. Other points of dif- 
ference are the absence of purifiers and bran and shorts dusters. In 
spite of these differences, a skillful and experienced operator is able 
to accomplish results on this mill which compare favorably in quality 
and efficiency with the work of commercial mills. An approxima- 
tion of the procedure followed and the sizes of cloths used are given in 
Figure 11. 
To accomplish the five breaks shown on the flow sheet in Figure 
11; the first stand of rolls, having 16 corrugations per inch, is used 
for the first and second breaks, the second stand with 20 corruga- 
tions per inch is used for the third break, and the third stand of 
rolls, having 24 corrugations per inch, is used for the fourth and fifth 
breaks. In those instances where one stand of rolls is used for two 
breaks, the rolls are reset when changing from one break to the other 
to grind to the fineness desired. The speed differential of the break 
rolls is 2h to 1. 
The smooth rolls are used for the middlings and tailings reductions. 
The reduction of the different grades of middlings stock on these rolls 
is merely a matter of proper adjustment. The speed differential of 
the smooth rolls is H to 1. 
The sifter is so constructed that five sieves may be used at one 
time. The sieves used in the sifter in making separations from the 
first break grinding are, from top to bottom, clothed with No. 16 
wire, 30, 50, and 70 grit gauze, and 10 XX silk, respectively. The 
sieves used for the separation of stock from the second, third, fourth, 
and fifth breaks are. with the exception of the top sieve, the same as 
for the first break. The top sieve used for sifting second break is 
clothed with Xo. 18 wire, third and fifth breaks with No. 20 wire, 
and the fourth break with Xo. 24 wire. 
The various grindings necessary for milling a sample and the size 
of sieves to be used in the sifter after each grinding are indicated on 
the flow sheet shown in Figure 1 1 . 
In milling a sample the ground material is transferred by hand 
from the rolls to the sifter and from the sifter to the rolls. All the 
separations resulting from each sifting are not removed immediately 
from the sifter, but some are left to accumulate through the sittings 
of several different grindings. 
The products — bran, shorts, and flour — obtained from the milling of 
a sample are weighed, the weights are recorded on the milling record 
sheet shown as Figure 9, and together with other weights recorded 
thereon form the basis for calculating percentage milling 3delds. 
A 150-gram portion of the flour is placed in an air-tight can for 
moisture, ash, nitrogen, and any other chemical determinations 
desired. The remainder of the flour is placed in a sample can and 
set aside for the baking test. 
This completes the milling of the sample. By following this 
procedure an operator can mill, depending on the character and 
condition of the wheat, from four to six 1,500-gram samples in a 7- 
hour day. The next step in the investigation of the sample is that of 
baking the flour. 
