|Gore Tex is
designed to allow moisture vapor to flow while
preventing access to water droplets. The ability
to transfer moisture vapor and to provide
waterproofing are often opposing requirements. On
the one hand, moisture vapor needs to be
transfered outward. On the other hand, water must
be prevented from migrating inwards. One requires
flow-through, the other requires a barrier.
high quality materials can allow this within
certain parameters, understanding how to keep
this breathable and waterproof system working
will go a long ways to achieving the desired
result and to maintain this performance over
Manufacturing a waterproof motorcycle boot is not
difficult. For example, rubber boots are very
waterproof. Unfortunately, they are low on the
comfort scale. They offer no permeability to vent
moisture, no breathing. The challenge becomes to
manufacture a waterproof motorcycle boot that is
also comfortable to wear.
what is Gore Tex?
Tex is a waterproof inner membrane that is
composed of holes, much like perfed leather. In a
Gore Tex membrane, the holes are big enough to
allow vapor molecules through but are too small
to allow water molecules to penetrate. So it's
really like a filter or screening mechanism. If
you're a vapor molecule, you get a green light.
If you're water molecule you get a red light.
in a name?
a note on breathable membranes. Not all
breathable membranes are created equal. Gore Tex
is an established brand that has performed over
time. There are other quality breathable
membranes that also perform well. But some just
carry the a designation stating breathable and
waterproof, while performing quite poorly when
judged on their ability to transfer water vapour.
So buyer beware.
a Gore Tex membrane to perform optimally and as
intended, it must work as part of a system.
Internal moisture must have an open path that
vents to atmosphere and there must be positive
pressure on the inside to push the moisture
the process is:
||Body emits moisture: this
heated moisture increases the pressure on
inner side of the Gore Tex membrane. A
Gore Tex membrane relies on this positive
pressure to drive the moisture through
the membrane and on to the next stage.
||Moisture is pushed through
the Gore Tex waterproof membrane. The
principle is that the hotter you are, the
more heat and moisture that you generate.
This increases the pressure available to
pump the moisture through the Gore Tex
membrane. No positive pressure equals no
||Moisture is then is
absorbed by leather and wicked to the
outer surface where it is evaporated to
If there is an obstruction
impeding the flow in this process, performance
Considerations for Gore
Typically, waterproof leather will
be used in Gore Tex boot applications. This
leather limits the amount of water that it
absorbs and, more importantly, allows it to flow
moisture vapor (what we refer to as being
A Gore Tex membrane will only work
within a system where all the components are
permeable to moisture vapor ie the Gore Tex
membrane, the inner liner, and the leather.
Clogging one of these components, will
significantly reduce the effectiveness of the
Gore Tex membrane.
Think of this like the exhaust
generated by an engine. The harder an engine
works, the more exhaust it produces and the more
pressure this exhaust gas will generate. You can
have a tuned and high performance header system
and pipes, but if you obstruct the exhaust
cannister, you get an increase in back pressure.
The more the exhaust cannister is obstructed, the
higher the back pressure. An effective exhaust is
all about flow. In the same way, effective
transfer of moisture vapor is also about flow.
If we apply traditional
waterproofing agents on waterproof leather ie
oils, creams, or greases, we obstruct this
breathability by clogging the pores of the
leather. This is similar to obstructing the
With vapor having nowhere to go
when it hits the now clogged leather surface,
pressure will build between in the inside and
outside of the Gore Tex membrane, impeding
directional flow. The inside moisture ie next to
your socks, will condense, leaving you with
clammy-feeling wet socks. This is similar to what
happens when you wear a pair of rubber boots. So,
in effect, you lose the comfort advantage of
breathable waterproof leather boots. The leather
may then become somewhat more waterproof but at
the detriment of having wet feet resulting from
inner vapor condensation.
Making your leather waterproof by
applying a product that clogs the leather pores
(ie provides a physical barrier to water) tends
to nullify much of the benefits offered by the
Gore Tex membrane. So, what to do?