Moisture Management

The Problem

Moisture management is a part of active outdoor activities.  As you exercise, your body produces moisture in the form of sweat.  At the same time, being outdoors, means you may be subjected to  rain and snow.  In either case, if your insulating garment becomes wet, it will loose all or part of its insulating ability.  Using a waterproof shell will eliminate the issue of getting wet from the outside, but it will simply exacerbate the  problem of getting wet from the inside.

Garment permeability

Permeability is the ability of a garment to  transport water, vapor or air.  

Constantly evolving garment technology is changing the traditional clothing design goals for permeability by actually increasing permeability in garments designed for highly aerobic activities.  These garments can place a premium on moisture removal at the cost of warmth when speed or wind increases.

The bottom line is that you want to achieve garment permeability that is commensurate with the moisture you will introduce for a given level of exertion.

Permeability Testing

Our laboratory equipment provides several modes of testing for water and vapor permeability.

Our drying test investigates how rapidly a garment can transport and remove liquid water.  The  test applies low level heat to a wet garment.   As the garment dries, surface temperature of the garment increases and vapor pressure beneath the garment decreases.  When the garment is dry, the garment temperature will cease changing at approximately ambient temperature and the vapor pressure will equal ambient room vapor pressure.   We produce time lapse thermal video of the drying process as well as plots of vapor pressure changes and temperature changes.  The quantitative data may be used to compare the drying characteristics of  fabrics, base or intermediate layers or outer garments.

Our wicking test places a known quantity of water beneath the test garment.  Low level heating is applied.  Similar to the drying test, we measure top surface temperature of the garment, temperature and vapor pressure below the garment.  The thermal imager permits us to visualize the spread of moisture across the garment as wicking occurs.  Of course, we can observe the rate of wicking/drying and compare this characteristic across garments.

Vapor transmission through waterproof/breathable membranes can also be measured.  We introduce a known quantity of water and low heating.  This test monitors vapor pressure across the test garment.  The amount of vapor pressure differential that drives vapor transfer distinguishes one membrane solution from the next.  More effective membrane solutions transfer vapor at reduced pressure. Our test system  measures the vapor pressure differential and can identify the conditions under which  a garment performs effectively.  

All of these tests allow us to measure grams of water moved per minute.

The Bottom Line

Our array of tests permits us to quantify drying, wicking and vapor transport and provide objective comparisons of competing products. 

Below  are examples of drying and wicking thermal time lapse videos.

Dry Test: Two Base Layers

This test compares drying for two base layer garments.  When the test starts, the garments are cold and show low temperatures (purple).  As they dry, surface temperatures rise.  When the garments are dry, the surface temperatures stabilize.  The video shows a substantial difference in drying performance between the two garments.

Drying Tests Quantitative Data

These plots show surface temperature and partial vapor pressure plots that correspond to the dry test video.

As is seen, when the samples are dry, the temperatures and vapor pressure differentials stabilize, allowing the dry time characteristics to be recorded and compared.

The plots show the significantly different drying performances of the two products being compared.

Wick and Dry Testing of Two Base Layers

In this test, a water source is placed in contact with each garment at two locations.  The garments wick water from the sources until saturation is achieved.  The water then begins to dry.  At the end, the outline of each water source is seen, but the sources have dried to that point that wicking is no longer supported.

The left garment wicks more water   then the right garment.  Drying times are similar for the two, but the left garment moves more water then the right garment.