Use of Sulphite Cellulose Extract as a Tanning Material Page: 314
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Technologic Papers of the Bureau of Standards
desirable property. The Ph values of solutions of analytical strength
ranged from 2.86 to 3.50 as compared with a range of from 3.7 to 4.7
for such generally used materials as chestnut wood, hemlock bark,
wattle, oak bark, mangrove bark, and quebracho wood extracts.
2. TANNING EXPERIMENTS
The analyses described above showed that sulphite cellulose
extracts contained materials which would combine with hide sub-
stance and would, therefore, be termed "tannins." The next work
involved a number of trial tanning tests in which pieces of calfskin
and samples of hide powder were tanned with these extracts alone.
The results demonstrated that the hide substance was converted
into a nonputrescible form which would withstand prolonged washing
with water at ordinary temperatures without reverting to a raw
condition. In other words, leather was thus produced. A series
of experiments were then planned and conducted to indicate the
value of these materials for tanning purposes.
(a) COLOR TESTS.-In the manufacture of leather, particularly
sole leather, color plays an important role. In order to be mer-
chantable, the leather first must have a satisfactory color although
the latter bears no relation to the most desirable property, that of
resistance to abrasion. Satisfactory color is practically indefinable
as a term and there are many varieties from which to choose. In
general, however, the leather must have a uniform, light color to
suit the requirements of the shoe industry. Thus it occasions no
surprise that the tanner inquires as to what effect any proposed
new material will have on the color of his finished leather, and further
as to whether its use will aid in producing the color desired. These
tests are usually carried out by tanning pieces of sheepskin or calfskin
skivers (thin grain thicknesses of the skin) by procedures, which
experience has shown give a satisfactory indication of color.
After trying several methods of making color tests the following
one was found to be most satisfactory. The method is given because
of the difficulty some have experienced in making color tests with
sulphite cellulose extracts, synthetic tanning materials, and other
special materials proposed for use in leather manufacture. A
sample of sheepskin skiver (6 by 6 inches) was removed from the
sodium chloride preserving solution and washed out in distilled water
and then placed in 400 cc of a 200 barkometer (sp. gr. 1.02) liquor
made from the material to be tested. The solution was shaken
periodically and allowed to stand for 24 hours, after which the skiver
was removed and washed for 24 hours with several changes of water
and then placed in distilled water overnight, and finally rinsed.
Next the skiver was drained for 30 minutes and then placed on a
[ vol. 2l
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Wallace, E. L. & Bowker, Roy Clement. Use of Sulphite Cellulose Extract as a Tanning Material, report, November 1, 1926; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc66515/m1/6/: accessed April 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.