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If you’ve shopped for rain gear lately, you’ve noticed that top clothing manufacturers produce lightweight jackets made from “breathable” materials. Jackets aren’t living things, so how can they breathe?
The technical term for breathability is called moisture vapor transfer, or MVT. The process works like a cold glass of water in a hot room. Warm moisture in the air travels toward the glass, causing the outer glass to form sweat droplets. In the same way, warm body moisture on the skin wants to travel toward the layers of a cooler jacket.
“Our Omni-Tech products, like the HydroTech Packable jacket, provide waterproof and breathable protection by keeping outside elements from getting in, while still allowing moisture vapors to move away from the skin,” says Krystl Tonkin, a marketing specialist at Columbia Sportswear. “Microporous membranes permit air passage while keeping water from penetrating the fabric allowing perspiration to escape so anglers stay dry.”
Hydrophobic and hydrophilic coatings are sometimes added to fabrics to help pull the moisture away from the skin. This helps when outside heat and body moisture are similar temperatures. Put simply, the hydrophilic coating on the inside of the fabric attracts the moisture, then the hydrophobic lamination on the outside forces the wetness away.
“Frequently, a numerical rating is used to assess how waterproof and breathable a jacket is — something like 10,000 millimeters/5,000 grams — in an effort to help consumers measure the garment’s properties,” says Ron Ballanti, with Grundens.
The second number (5,000 grams in this example) refers to the amount of water vapor that can travel from the inside to the outside of 1 square meter of the fabric over a 24-hour period. The higher the number, the more body moisture is allowed to escape through the fabric itself.
A breathability rating of at least 3,000 grams means the jacket does a suitable job of dissipating body moisture as long as the fisherman is wearing the proper wicking layers underneath, Ballanti says. But MVT ratings get much higher than that: Grundens Burning Daylight jacket is manufactured from a heavy-duty material that still provides breathability up to 10,000 grams.
In the past, some anglers were turned off from the nomenclature of “waterproof.” A number of jackets that were said to be waterproof still allowed water to leak at the most inopportune times. That, or you had to use a heavy, insulated jacket that kept the rain away, but left you sweaty and stinky. Today, clothing manufacturers go to extremes to test their new jacket styles, even if it’s not storming outside.
“When we received the first-ever samples of our Waterproof Fishing Jacket, our president, Bill Shedd, wanted to test just how waterproof the jacket was,” said Casey Shedd, of AFTCO. “He decided to forgo his normal shower, and minutes later he stepped out of the bathroom perfectly dry and was excited to report that the jacket passed the ‘shower’ test. The jacket has since been tested on the water by countless pros.”