SIEVES 
171 
Sieves. — Tiny sieves are conveniently prepared from silk 
bolting cloth, drawn taut by means of small rings, one slipping 
over the other in the manner of ordinary embroidery rings. 
A convenient size has been found to be about 25 mm. for the 
inside diameter of the inner ring. The following values may 
serve as a guide in selecting the proper bolting cloth numbers 
corresponding to the Tyler Standard Screen Scale. 
Cloth Number. 
16.. .. 
15.. .. 
14.. .. 
13 ... . 
10.. .. 
9. . . . 
8 . . . . 
6. . . . 
4. . . . 
2. . . . 
o. . . . 
Approximate Standard 
Screen Meshes 
to inch. 
190 to 180 
130 
120 
no 
100 
80 to 90 
70 to 60 
50 to 60 
45 to 50 
40 
30 to 20 
These values were obtained by measuring the diameters of 
the largest openings with a filar micrometer and averaging the 
results. The sizes of the openings in bolting cloths are variable. 
The advantage of employing bolting cloth lies in the ease with 
which a tiny sieve may be prepared, moreover after using a 
disk of cloth it is thrown away; there is no need for economizing 
by cleaning it. 
These little sieves are useful only in roughly separating fine 
from coarse particles, but are not uniform enough to serve as 
classifiers. 
