When describing fabrics used in outdoor gear, two closely related terms are often used – “Waterproof” and “Water-resistant”. They refer to the degree to which a textile resists moisture and penetrates the water. You will learn more about What’s The Difference Between Waterproof and Water-resistant by LCNOutdoors article.
Where do you draw the line between “Waterproof” and “Water-resistance”?
Theoretically, there is none – water can penetrate or cut through materials under certain pressures. Therefore, technically, all fabrics can only be considered “Waterproof” to a certain extent. In addition, in industry, the term “Water-resistant” usually refers to the resistance of a material to water damage/softening.
For this reason, manufacturers of functional fabrics, in general, use the terms “Waterproof” and “Water-resistant” to describe the properties of their products, meaning the ability of a textile to keep water from passing through or getting wet under certain conditions.
The term “water-repellency” is sometimes used by manufacturers as a synonym for water resistance. waterproof is a material that can trap water from the external environment only under certain conditions and for a relatively short period of time.
Waterproofing of fabric is achieved by applying a hydrophobic polymer layer based on Teflon or silicone to its surface. It creates a high surface tension that allows water to collect into droplets that roll off the fabric without penetrating into the fabric.
A prime example of a Waterproof fabric is a textile that has been treated with a water repellent impregnation. If the water pressure is kept within a certain range and the impregnated polymer lies as a homogeneous layer on the fabric, water collects as droplets and rolls off the fabric. However, once the water pressure increases, the water finds a “hole” between the polymer chains and soaks into the fabric. The same thing happens if the fabric is damaged or if the impregnation layer is not applied uniformly.
The fabric becomes impervious to water in two ways.
- by applying one or more layers of a non-absorbent polymer, such as PVC, silicone, or polyurethane. This method is commonly used to make our garments such as awnings, backpacks, and compression bags watertight because they do not require the intensive discharge of evaporated water. The more layers of polymer applied to the fabric, the higher its water resistance and weight.
- The fabric is attached to a membrane that is impermeable to water in liquid form, but is capable of transmitting water vapor. Because of the breathability (water vapor permeability) of the resulting material, it is used to make fabrics for outdoor clothing used for active recreation and sports. The technology of the membrane itself and how it is bonded to the face fabric will affect its ultimate waterproofness, which can vary greatly.
How The Water Repellency Of A Material Is Determined
The so-called “hydrostatic test” (JIS 1092 Method A; AATCC Test Method 127) is used worldwide to determine the water-resistance of a material. According to this method, fabric samples are washed 10 times to approximate the real conditions of use. A special machine is then used to apply a pressure equivalent to a column of water of a certain height in millimeters over an area of 0.001 square feet (1 square centimeter). Another unit of measurement is psi – pressure in units of area per square inch (1 psi = 704 mm water column).
The test described is not the only method, and there are variations – for example, water pressure can be applied quickly or gradually, and fabrics can be tested not only after washing but also when new.
What Materials Can Be Considered “waterproof”?
Although there are few variants of the hydrostatic test and all give almost identical results for the same test samples, fabric, and garment manufacturers disagree on which numbers allow material to be called “waterproof” in the “domestic” sense.
You can see many numbers being quoted. the REI Quality Lab considers fabrics with a water column of 2,112 mm to be watertight based on their testing. The European standard EN-343 suggests a more conservative figure of 1,300 mm, even after the fabric has been washed and dry cleaned five times. U.S. military authorities have several standards and definitions for what constitutes an impervious fabric, according to REI. And the declared values for clothing, tents, and backpacks can vary. Some membrane fabric manufacturers contribute to this difference of opinion, with thresholds ranging from 10,000 to 23,000 mm watertight.
Compounding the problem is the fact that there are no reliable studies today to determine how much water pressure a person faces in severe weather. From time to time, it has been mentioned on the Internet that rain with hurricanes can produce a maximum water pressure of 7,040 mm. Or, in some cases, a person may generate too much pressure on the fabric-for example, when a 165 lbs (75 kg) hiker gets down on one knee, he generates about 11,000 mm of pressure, and when he sits, he generates about 6,000 mm of pressure. Unfortunately, these figures are not supported by calculation methods, experimental tests, and reliable sources.
However, special internal standards have been developed for the production of waterproof clothing and equipment for sports and outdoor activities, based on data obtained from laboratory and field tests.
“Water resistance” of the membrane
For membrane fabrics, the minimum barrier to obtain a “waterproof” status in practice is about 10,000 mm of the water column. This material is capable of withstanding continuous rain of any intensity, wet and dry snow, high humidity, and fog. This figure even includes some guarantees for the inevitable wear and tear of the material. As you can see from our table, this waterproofing figure is common to many of the films used in the industry, including the economical and top-of-the-line films – Texapore, NanoPro, Shelter Neo+, Neoshell.
Tips: But why are there membrane materials in the industry that have a prohibitive waterproofing value of 20,000 mm or more, well beyond the required value?
Alas, but it is impossible to get a definitive answer to this question. Obviously, the particularities of the production process and raw materials of this membrane simply do not make the material less waterproof. However, for the user, it brings certain advantages. A membrane with a water resistance of more than 20K is a strong guarantee against leakage under absolutely all forms of precipitation during long-term operation. Provided that the material used maintains its mechanical integrity.
Watertightness of plastic-coated fabrics
Due to their lack of unique “breathing” properties, these materials are hardly used in the manufacture of sports and outdoor clothing – except for various ponchos, ponchos, and capes. However, they are actively used in the manufacture of tents, backpacks, rain bags, and other equipment that require some degree of protection from precipitation.
Compared to waterproof membrane fabrics, this group of materials has decidedly more average waterproofing properties, rarely exceeding 10,000 mm. However, they succeeded in protecting us and our equipment from all types of precipitation and its duration. Perhaps for this tissue, the value of 2,112 mm of water column mentioned by REI Labs would be the threshold for the material to be considered “waterproof”.
What Kind Of Waterproofness Do I Need?
This is usually the question users ask when purchasing a windproof jacket. Based on published water resistance data and practical applications, membrane materials used today can be divided into three categories.
- Up to 10,000 mm – These materials do a good job of protecting their owners from light and brief precipitation and “dry” snow. These cannot truly be called “waterproof.” SoftShell and more affordable membrane-type garments are often waterproof.
- from 10,000 to 20,000 mm – a broad group of different levels of membrane fabrics – from budget to top of the line. These membranes are used to make storm weather garments that can withstand continuous rain or slushy snow combined with windstorms.
- from 20,000 mm – membrane materials provide absolute protection against all types of rainfall and guarantee long-term water resistance.
The variation in the assessment of fabric water resistance that we have described has led many manufacturers today not to publish specific figures and data to avoid false comparisons. Often, they simply guarantee the waterproofness of their materials or garments under product design conditions without reference to test data.
When choosing a rash guard, it is never a good idea to chase exceptionally high waterproofing values. The vast majority of membrane materials used today, sometimes even at the budget level, provide high levels of waterproofing with adequate reserves. What is more important is their breathability, as well as the cut of the garment, the fabric in front, and the accessories used in it.
It is also important to remember that it is not just the materials used that make a garment waterproof. The sealing quality of the seams, the waterproof impregnation used on the front of the material, and even the cut features all have an impact.
The material is based on publicly available laboratory data from REI, MSR, and W.L. as well as test specifications based on various quality standards.