Understanding Waterproof Ratings & How Testing Is Performed
By Treas Manning
Every sales associate in every ski shop talks about the waterproof rating of a particular piece of skiwear. Many depend on the manufacturer’s product hangtag and some actually pay attention during the product clinics given by the company’s tech rep. But sadly, very few ski shop employees really understand the testing technique or what the rating actually means. Here we go, a straight forward description of waterproof testing and what those darn mm numbers mean.
STATIC COLUMN TEST
The Static Column test is remarkably simple and widely used throughout the textile industry. The Static Column is an acrylic cylinder that’s one inch in diameter and open on both ends. The bottom of the cylinder is outfitted with a watertight gasket or footing. The gasket is designed to keep the water from spreading out sideways once the cylinder is filled with water.
The cylinder is marked from bottom to top 0, 1-1k, 1k-5k, 5k-20k, 20k-40k. These numbers reflect the amount of water pressure on the fabric when water is filled to a particular mark.
The Static Column is placed on a suspended swatch of fabric and water is poured into the cylinder. If water starts leaking through the fabric at the 1k mark, your test is done and the fabric is assigned a 1000mm or 1k rating. Translation, the more water pressure a fabric can withstand before leakage, the more waterproof it is.
See, I told you it was pretty simple…but wait, there are some outside forces that can mess the whole thing up. Let’s say you’re wearing a pair of 40k backcountry ski pants and you sit in the snow to move around and get comfortable. Believe it or not you are applying more pressure to the fabric. That’s why the seat of your pants will get wetter, sooner than other areas. What does this all mean? Now don’t be disappointed, but even a highly rated garment can, under the right circumstances, give way to water penetration. Bottom line, waterproof rating is not an exact science.
HOW YOUR SKIWEAR IS BUILT AND WHAT IT IS MADE OF WILL AFFECT HOW WATERPROOF IT WILL BE
2 LAYER SKIWEAR . GOOD
A 2L or 2 layer is a garment that’s constructed with 2 layers bonded together. The face or outside fabric is bonded to a waterproof breathable membrane. A 2L ski jacket is going to be lightweight, and tends not to be as bulky as a 3L, therefore it will be easier to stuff into a backpack and takes up less space.
Now remember, the waterproof breathable membrane is on the inside of your ski jacket and exposed to wear and tear from rubbing again whatever you are wearing underneath. It is also likely to absorb sweat and oils from your skin and this is definitely going to effect the long term wear and performance of your garment, that’s the downside. The upside, like we already mentioned, the 2L tends to be lightweight and packable. It is also likely to cost less than a 2.5L or 3L garment.
2.5 LAYER SKIWEAR . BETTER (with some trade offs)
2.5L is a step up in the longevity of your skiwear item. Improved wear is achieved by spraying or coating the membrane to protect the garment. The upside of your garment is obvious, the life of the membrane will probably be longer if you haven’t really added much in the way of weight or bulk. This is a nice compromise if you are concerned about packability.
3 LAYER SKIWEAR. BEST (also with some tradeoffs)
A 3L garment is made up of the face fabric, the face fabric is bonded to the waterproof breathable membrane, and the membrane is backed with a protective woven fabric. The third layer is commonly known as scrim.
A ski jacket made with 3L construction is going to be more durable. It is also going to be heavier, thicker, and not as soft to the hand, but the life of the waterproof dependability will be greater. The downside, by adding the protective scrim to the membrane your garment will not be as breathable.
Lots of things to consider when selecting your skiwear. Cost, longevity, weight, packability, waterproofness, and breathability.
WATERPROOF BY CONSTRUCTION
CRITICALLY TAPED SEAMS
Seam tape has been added to the seams of your garment to the seams of your garment that are the most exposed to the pressure of driving snow or rain. Shoulder seams, seams down the front of your garment, and seams on the seat of your ski pants should be the areas taped. Seams that might not be taped would be the areas less affected by the elements. Side seams and under arm seams, and seams at the cuff are not as exposed to driving rain or snow and therefore are probably not taped.
The upside, not as costly as fully taped seams and not as much weight is added to your skiwear garment.
FULLY TAPED SEAMS
This one is pretty self explanatory, all seams are taped giving more protection from leakage. The downside, added cost and weight.
Seam welding is pretty cool technology. The panels of your garment are either glued together instead of stitched, or they are bonded with a sonic technique actually melting the seams together. The seams are less constricting than taped seams, and they're also less bulky. The seams will actually have a bit of stretch making your skiwear more comfortable, and because there is not seam allowance fabric or tape, your garment will be lighter than 3L. If that's not enough, welded seams are much more waterproof as they are stronger and more resistant to water pressure.
Yes, you guessed it; the process of welding seams is going to add to the cost of the garment.
It is important to consider your needs and constraints. Budget can be an obvious constraint. How much use will your garment experience? Are you a backcountry skier where packability, breathability and waterproofness are a big concern? What about comfort?
FYI: A little side not. Ever wonder why Gore-Tex costs more than many other waterproof breathable treatments?
Gore-Tex understands that outerwear is only as waterproof as the design features of the garment. A ski jacket can be built with top of the line 3L waterproof breathable membrane. But if the seams aren't taped or welded, if the zippers are not waterpoof or protected with an inner and outer storm flap, water will eventually find its way in.
That's why Gore-Tex requires that manufacturers seeking to construct their garments with their membrane technology, must submit a prototype to be put through the riggers of waterproof testing. A Gore-Tex garment must also be waterproof by design.