We now leave the physiological class and take up those tanning
materials included in the pathological class, or those of abnormal
growth.
_Galls_.--These are not consumed to any great extent at the present
period, but formerly they were used quite extensively. The galls are
found upon the leaves of the oak or sumac, etc. The direct cause of
their growth is that a certain wasp (cynips galles) stings into the
leaf and after depositing its egg, flies away. The egg develops into a
larva and then into a full-fledged wasp, boring its way out of the
gall which has served as a protection and nourisher. This accounts for
the hole noticed in almost every gall. The different varieties include
Aleppo. It is found upon the same trees as the valonia and contains 60
to 75 per cent. tannin; Istrian galls, 32 per cent. tannin; Persian,
28 to 29 per cent. tannin. Chinese galls, giving 80 to 82 per cent.
tannin, are the results of the sting of a louse, and make a very
light-colored leather. The dyers also use this material for coloring.
_Knoppern_--Belongs to the family of galls, and is a most important
factor of commerce in Austria. The knopper is generally found on the
acorn or leaf of the oak tree. The greatest quantity is derived from
the steel oak of Hungary. The tannin contained varies from 27 to 33
per cent. Knoppern are not being used so much now as formerly, and
consequently the amount harvested lessens from year to year. Its main
use was and is in combination with valonia as layers for sole leather.
Valonia gives better weight results than knoppern, and is replacing
knoppern more and more every year. The combination of knoppern,
valonia and myrabolams is also quite popular, and gives good results.
Knoppern are seldom used alone, being generally combined with some
other tannin. Austria is almost the only consumer at present, but
Germany used it extensively formerly.
_Bark and Wood Extracts_--Are becoming general favorites throughout
Europe, partly because of their weight-giving qualities and partly as
the transportation costs so little; they can be used to strengthen
weak bark liquors.
_Oak Extracts_--Are well liked, both wood and bark, and are used
extensively. Slavonia furnishes a great deal of it.
_Chestnut Oak Wood Extract_--Is manufactured in quantities, and easily
finds purchasers.
_Pine Bark Extract_--Is also consumed in goodly amounts.
_Quebracho Wood Extract_.--The wood is shipped from Brazil to Hamburg
and other ports, and the tannin extracted there. Hamburg furnishes
quantities of it.
_Hemlock Extract_--Is used in Russia, and seems to have taken a hold
on the shoe buyers' fancies, as they now make imitations of it in
color. The hemlock that is consumed is imported from America.
As most leather is sold by weight in Europe, the leather manufacturers
aim to obtain as good weight results as possible, and often, I am
sorry to say, do so at the sacrifice of quality. This is common to
both upper and sole leather. Sole leather is nine times out of ten
given false weight by forcing entirely foreign substances into the
leather, such as glucose, barium chloride, magnesium chloride, resins,
etc. Glucose and resin are also used for weighting upper leather.
Leather is also weighted with extracts by overtanning. Leather buyers
have become very wary of late and do not purchase large quantities
before an analysis is made of a fair sample.
One more word before I close. The governments and private individuals
in Europe cultivate and raise trees for both lumber and bark purposes.
The forests are excellently cared for by efficient foresters, and the
result is that the tanners obtain much cleaner and better bark, and of
a very even quality. Would it not be a good idea if some individual,
who would certainly earn the everlasting gratefulness of the tanners,
would look into this matter, and see that not only the lumber side of
our forest cultivation is not neglected, but that the bark also is
preserved and cared for? Of course, we can obtain all the bark
necessary at present and for some time to come, but the time will come
when we shall certainly regret not having taken these steps, if the
lumbermen and bark peelers go on devastating magnificent forests.
Below will be found a table of weight results. Sole leather tanned
with these materials gives for every 100 lb. green hide the following
quantities of finished leather:
lb.
Oak bark 48 to 54
" extract 55 to 56
Pine bark 44 to 46
" extract 48 to 50
Willow 45 to 46
Birch bark and oak extract 49 to 51
Quebracho wood and extract 48 to 49
Valonia 52 to 56
Knoppern 51 to 53
Myrabolams 50
Knoppern, myrabolams and valonia 52 to 53
Hemlock 55
Specification of tanning materials used in different countries:
_France_.
Oak bark (kirmess).
Sumac.
Chestnut wood extract.
Quebracho " "
Some gambier.
_Italy_.
Oak bark.
Pine "
Sumac.
Valonia.
_England_.
Oak bark.
Divi divi.
Myrabolams.
Valonia.
Mimosa.
Extracts { Oak bark and wood hemlock.
Gambier.
Cutch.
_Germany and Austria_.
Oak bark.
Pine "
Willow bark.
Valonia.
Knoppern.
Myrabolams.
{ Oak bark and wood.
Extracts { Pine bark and wood.
_Russia._
Birch bark.
Willow "
Oak "
Pine "
Hemlock extract.
_Norway and Sweden_.
Birch bark.
Willow "
Oak "
WALTER J. SALOMON.
--_Shoe and Leather Reporter_.
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