38 BULLETIN 882, U. S. DEPARTMENT OF AGRICULTURE. 
Table 15. — Effects of mercerization upon construction of cloth. 
Diameter of yarn. 
Dimensions of Variations in 
interstices. ] diameter of yarn. 1 
Warp. 
Filling. 
Warp. 
Filling. 
Warp. 
Filling. 
Inches. 
0. 008393 
. 007873 
Inches. 
0.008718 
. 008491 
88? 
01=0 
oco* 
Inches. 
0. 004500 
. 004330 
11-18 
12-17 
12-19 
11-17 
1 The figures in this column may be converted into inches by multiplying by 0.03937 and dividing the 
result by 70. 
Having determined the various properties of the fabric composed 
of 3/80's yarn, further tests were made to determine if the ideal 
conditions of equal stretch in the warp and filling could be obtained 
for the 2/60's fabric through piece mercerization. Sea Island cot- 
ton was used for this experiment and cloth made according to the 
Signal Corps Specifications 16,004— A was tested. This cloth was 
sent to two finishing plants for mercerizing in the piece, without 
direct supervision by the personnel ~of the Bureau of Markets, so as 
to furnish an indication of what might be expected of cloth of this 
description under normal commercial conditions of mercerization. 
The results corroborated the conclusions drawn from the tests on 
the 3/80's cloth. These results are shown by Table 11 and also by 
Figure 17. 
DOPING. 
In order to give the airplane wing the smoothness, tautness, and 
rigidity necessary to minimize the wind resistance, a solution com- 
monly termed " dope " is applied. Doping usually consists of the 
application of several coats of either cellulose acetate or cellulose 
nitrate, or both, and is followed by a single coat of varnish to make 
the fabric waterproof. 
A representative of the Bureau of Markets visited an airplane 
factory in order to study the methods of application of the dope to 
fabrics. Several conferences were held with the experts of the 
factory and an analysis was made of a doped sample. As a result the 
following method was adopted for comparative tests on the doped 
fabrics made from the different varieties of cotton and also for com- 
parative tests to determine the best weave. It was thought that these 
conditions approached as nearly as possible those that prevail in 
airplane factories. 
(a) Four coats of dope and one coat of varnish, weighing approximately 60 
per cent of the fabric, were used. 
(b) Nitrate dope used exclusively. 
(c) Fabric stretched under 5 pounds floating load. 
