10 
BULLETIN 1168, U. S. DEPARTMENT OF AGRICULTURE. 
tent (lots 8 and 9 and lots 29 and 30), however, show the smallest 
differences in wear. Approximately 8 per cent greater wear is shown 
for the loaded leathers. Had the tests been conducted in a damper 
climate this result might have been quite different. 
Differences between certain regular brands of leather used in these 
experiments permit an additional comparison showing the effect on 
the wear of low and high glucose and epsom salts content. 
Data secured on 90 soles from 5 lots, consisting of only regular 
brands of sole leather having less than a total of 3 per cent of glucose 
and epsom salts, were assembled. The total glucose and epsom salts 
content varied from 1.23 to 2.99 per cent and averaged 1.95 per cent. 
The average days wear per 9 irons for all lots was 80. 
Data secured on 249 soles from 12 lots, consisting of only regular 
brands of sole leather having more than a total of 7 per cent of glucose 
and epsom salts, were assembled. The total glucose and epsom salts 
content varied from 7 to 11.08 per cent and averaged 8.92 per cent. 
The average days wear per 9 irons for all lots was 80. 
The results of this comparison may seem to disagree with those of 
the first comparison (p. 9). In the first comparison, however, 
the two sets of leather having the greatest differences in glucose and 
epsom salts content show no differences in wear. Therefore the indi- 
cations from all these tests are that, within the limits noted, the 
content of glucose and epsom salts does not materially affect the 
wear of shoes in a dry climate. 
Effect of Rolling Leather. 
The wearing qualities of rolled leather from regular brands were 
compared with those of unrolled leather from the same brands. 
The results are given in Table 4. 
Table 4. — Effect of rolling on wear of sol e leather. 
Lot 
No. 
Description of leathers. 
No. of 
soles, 
Composition of original leather (moisture- free basis). 
Total 
ash. 
Petro- 
'eum- 
ether 
ex- 
tract. 
Un- 
com- 
bined 
tan- 
nin. 
Non- 
tan- 
nins. 
Water 
solu- 
bles. 
Ep- 
som 
salts. 
Glu- 
Hidc 
sub- 
stance. 
Com- 
bined 
tan- 
nin. 
Aver- 
age 
days / 
wear 
per 9 
irons. 
Oak tannage: 
Regular 
Same as lot 5 except 
unrolled 
Chestnut tannage: 
Regular 
Same as lot 16 ex- 
cept unrolled 
Regular 
Same as lot 20 ex- 
cept unrolled 
Per 
cent. 
1.01 
.94 
1.14 
.94 
1.48 
Per 
cent. 
2.03 
2.18 
2.75 
2.34 
2.38 
Per 
cent. 
16.56 
14. 89 
15.77 
15.82 
13.44 
Per 
cdil. 
9.39 
12.29 
9.30 
16.32 
Per 
cent. 
25. 95 
23.28 
28.06 
25.16 
29.76 
Per 
cent. 
1.37 
1.47 
3.19 
3.28 
3.71 
2. 56 13. 35 
29.70 4.02 
Per 
cent. 
1.08 
1.10 
5.03 
3.13 
6.90 
6.28 
Per 
cent. 
40.04 
40.45 
41.23 
42.21 
44.05 
42.50 
Per 
CI lit. 
31. 85 
33.87 
27.84 
30.19 
23.64 
25.11 
The results in Table 4 indicate that a well-rolled, compact leather 
wears longer than a corresponding unrolled leather. Approximately 
16 per cent longer wear is shown for the rolled leathers. These 
indications support the regular tannery practice of rolling sole leather 
to make it firm and compact. 
