We deem it advisable, in order to examine the hide properly so-called,
to dispense with those eradicable substances which may be regarded, to
some extent, as not germain to it, and confine our attention to the raw
stock, freed from these imperfections.
It is well known that a large number of vegetable substances are
employed as tanning agents. Our researches have been directed to leather
tanned by means of the most important of these agents.
Many questions present themselves in the course of such an examination.
Among others, that most important one, from a practical point of view,
of the weight the tanning agent gives to the hide, that is to say, the
result in leather of weight given to the raw material. The degree of
tannage is also to be considered; the length of time during which the
tanning agent is to be left with the hide; in short, the influence upon
the leather of the substances used in its production. That is why we
have made the completest possible analysis of different leathers.
Besides ordinary oak bark there are used at present very different
substances, such as laurel, chestnut, hemlock, quebracho and pine bark,
sumac, etc.
Water is an element that exists in all hides, and it is necessary to
take it into consideration in the analysis. It is present in perceptible
quantity even in dry hides. This water cannot be entirely eradicated
without injuring the leather, which will lose in suppleness and
appearance.
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