When it comes to providing a range of clothing that will keep you protected and cool at the same time, you’re going to be looking at those garments made up of breathable materials. But what exactly is a breathable fabric?
Breathability in a nutshell is the ability for a fabric to allow moisture vapour to pass through the material, thus helping you to stay cool. This is done through a measurement of how quickly moisture can pass through a fabric, otherwise known as the moisture vapour transmission rate (MVTR).
Why is this a good thing?
Over the course of a day, we all begin to perspire due to the various tasks we undertake. When wearing garments that offer little to no breathability, this perspiration becomes trapped between yourself and the garment, resulting in your clothing becoming damp and clammy. While you may think this is more of an annoyance than anything, it can have serious health issues within certain scenarios. As a rule of thumb, water is much more thermally conductive than air. This means that when you become wet, you can become cold extremely quicker than if you are wearing dry or breathable clothing. If you are outdoors or in an area that already has a low temperature, this can lead to a number of health issues including hypothermia, painful joints and the common cold.
How is a fabric breathable?
There are two ways in which a fabric can be breathable. This is achieved through either standard ventilation within the garment or diffusion through synthetic fabrics such as Gore-Tex.
While breathable fabrics are meant to always provide you with a way to keep cool through the expulsion of water vapour, there are scenarios in which the breathability of a fabric can slow or completely stop altogether. If the outside air is very humid it caused the air to become saturated with water vapour particles. This means that when you perspire, there is simple to where for the water vapour to go so rather than evaporating through your breathable fabric, it just clings to your skin causing you to become damp. When you are in areas of extreme humidity there is no breathable garment that will be able to stop you getting damp.
Tests for Breathability
There are 3 tests used to check the breathability of a fabric. These tests are used to determine the Moisture Vapour Transmission and the Resistance of Evaporation of a Textile. The three tests are:
The Upright Cup Test
The fabric is placed onto a cup which is then sealed. The cup in then left over a period of 24 hours to see how much moisture has passed from the fabric and into the cup. Once the duration is up, the cup in then weighed to see how much moisture has passed through the fabric. The more moisture that is recorded in the cup, the more breathable the fabric is.
The Inverted Cup Test
In this test, the fabric to be tested is placed onto a waterproof membrane and submerged within a measured amount of water. An inverted cup is then placed on to the top of the fabric and held in place for 24 hours. Once the test is complete, the cup is then weighted to see how much water was been collected by the fabric. This allows a determination to be made as to the Moisture Vapour Transmission Rate of the fabric.
The Sweating Hot Plate Test
The fabric is placed on to a heated metal plate which is used to simulate the creation of human body heat and the subsequent sweat produced as a result . The plate is then kept at the same heat with the with the evaporation process recorded. This then records how much energy is needed to keep the plate cool, allowing the Resistance of Evaporation of a Textile to be determined.