Quote:1. The Technique of Water-Hardening Leather.
Vegetable tanned leather is initially soaked in water for long enough to wet it through
completely. This takes approximately 10 minutes. If the soaked leather is then placed in a
pot of water which has been pre-heated to 180
̊
C, it will begin to
change in shape and
texture.
After approximately 60 seconds, the leather dark
ens, goes limp and begins to curl up. If
extracted at that stage, it will have shrunk a bit, thickened slightly, and still be able to be
stretched, such as a sheet of rubber. At this stage - it is possible to stretch and form the
leather into required shapes. After a minute or
two, the stretchiness goes away, however,
the leather will still be fairly flexible. After air-drying for a few hours, the leather becomes
increasingly stiff, thickens slightly and becomes harder.
The longer the period of time that the leather is left in hot water, the more it shrinks, the
darker it gets, the thicker it becomes, and the
harder the finished product is. Sufficient time
in hot water will render leather into something which resembles wood, however, as with
most natural things, the process does have a tr
ade-off, in that the ha
rder the leather, the
more brittle it becomes. In the case of actual armour, it is likely that the leather would have
been hardened to the maximum, and replaced
after every battle. For purposes of re-
enactment or the making of object d-art - it
is desirable to harden
the leather without
detracting from it’s strength.
Approximately 30 seconds of immersion is usually sufficient to harden leather to a suitable
state - where the leather is hardened but still flexible - and results in a shrinkage of approximately 1/8
th
the original size (i.e. the
finished article will be 7/8
th
the size of the
original) and an increase in thickness of approximately 25%.
Due to the fact that the process is very temperat
ure sensitive, it is advised that an accurate
thermometer is used. To a certain extent, the finished product will also be dependant on the
leather itself, and experimentation with scrap leather is recommended. While being guided
by the clock, allow yourself to learn how the different types of leather behave and work
according to the changes you observe during th
e process as it proceeds in order to achieve
the end result you desire.
The Cuir Bouilli process can be considerably shortened by the use of boiling water. Thirty
seconds of immersion in boiling water will result in a shrinkage to 7/8
th
of the original size
and 40 seconds immersion in boiling water results in a shrinkage to 2/3
rd
of the original size
and approximately doubles the thickness of the original leather.
The use of boiling water has the advantag
e of speed and removes the need for a
thermometer, however it does hold two distinct
disadvantages, viz. the
process is harder to
control, and secondly, the hotter water result
s in a less uniform hardening process. Patchy
softness or brittleness can caus
e surface cracks to develop over
a period of time, and makes
the lower temperature process more desirable
when producing items intended for long-term
use or as items of
art/functionality.
so how do I know if my leather has been vegetable tanned or not - and what kind of vegetable tans leather ?
seem simple enough - except for the part where it says to heat water to 180C - this isn't actually possible water only get to 100 and then it turns to steam
So we'll just substitute - 'boiling water' for that part, I think.
Actually she probably meant 80c - hence the later reference to a thermometer and boiling water being much quicker.
anyway seems simple enough to try a few scraps of the leather I have and see what happens. Sounds like what I'm after though.