How much rain a jacket can withstand depends on the hydrostatic pressure, but you can’t just look at the hydrostatic pressure. You also need to consider breathability.
As a technological product, the jacket is the safety guarantee for mountain friends. Before you go wired, buying a jacket will give you a lot of peace of mind. When it comes to jackets, mountain enthusiasts often focus on “how much rain they can protect against.”
To know how rainproof a jacket is, you only need to know the hydrostatic pressure, but this is not enough. You also need to pay attention to breathability so that it can be worn easily. More comfortable.
So, what is hydrostatic pressure?
1. Rainproofness of Jackets: Hydrostatic Pressure
When mountaineering, it is common to encounter rain and snow. Jackets are an important weapon to resist rain invasion. You definitely want a jacket that’s strong enough to keep you from getting wet. But how do you tell if it’s waterproof? It depends on an important parameter: hydrostatic pressure.
The key indicator of waterproofing of a jacket: hydrostatic pressure – Many mountaineers think that if water is poured on the jacket, if it does not leak, it means it is waterproof. In fact, this is not the case. In addition to the natural penetration of water, the pressure exerted by the outside world will also Forces water to penetrate the fabric. The level of hydrostatic pressure of a jacket indicates its ability to resist being penetrated by water.
The hydrostatic pressure endured by the fabric represents the resistance encountered by water penetrating the fabric. Under standard atmospheric conditions, one side of the sample is subjected to continuously rising water pressure until three water seepage points appear on the other side. The pressure value when the third water seepage point appears is recorded to evaluate the waterproof performance of the sample. (Source: GB/T4744-2013 “Textiles
Detection and Evaluation of Waterproof Performance by Hydrostatic Pressure Method”)
The higher the hydrostatic pressure, the better the waterproofness – the higher the hydrostatic pressure of a jacket, the greater its ability to resist water penetration. The stronger it is, the better the waterproofness is. The specific data are as follows:
Data comes from: GB/T4744-2013 “Hydrostatic Pressure Method for Detection and Evaluation of Waterproof Properties of Textiles”
After reading this table, you may be wondering, why does the waterproof performance of jackets need to be classified?
The heavier the rain, the higher the hydrostatic pressure required by the jacket – the waterproof performance of the jacket is related to the intensity of the rain. The heavier the rain, the larger the radius of the raindrops and the greater the closing speed, resulting in a greater “impact” on the jacket, which requires higher hydrostatic pressure to prevent the raindrops from “penetrating” the fabric.
Data source: Lou Chenyu “Research on Evaluation Methods of Waterproof and Moisture Permeable Function of Jackets” 2016 Modern Textile Technology Issue 1
…The larger the radius of a raindrop, the greater its speed. Raindrops vary in radius and finish at different speeds. (Source: Liu Junjie and Zhou Xiuzhi “General Discussion on the Final Speed of Raindrop Falling” Physics and Engineering Vol.20 NO.5 2010)
According to According to national regulations, the hydrostatic pressure standards for jackets are as follows:
The hydrostatic pressure resistance of finished products with rainproof function requirements is not less than 13kPa (approximately equal to 13000mm), and the hydrostatic pressure resistance of finished products with rainproof function requirements is not less than 13kPa (approximately equal to 13000mm). The hydrostatic pressure resistance is not less than 35kPa (approximately equal to 35000mm). (Source: GB/T 21295-2014 “Technical Requirements for Physical and Chemical Properties of Clothing”)
So, the heavier the rain, the higher the hydrostatic pressure required for the jacket. The pressure from backpacks, bodies, etc. will further increase the hydrostatic pressure requirements of the jacket.
The greater the external pressure, the higher the hydrostatic pressure required by the jacket – if you carefully observe the parameters of the tent, you will find that they only have a hydrostatic pressure value of 1200~5500mm to resist rain, while the jacket A hydrostatic pressure of more than 13000mm is required. The reason behind this is that the external pressures they bear are different.
When backpacking on a rainy day, the backpack will put a lot of pressure on the raindrops dripping on the surface of the jacket. If the hydrostatic pressure is low, the rainwater will be “pressed in” “The fabric, while having high hydrostatic pressure, will effectively resist rainwater penetration.
Similarly, when climbing in rainy or snowy weather, squatting, sitting, or leaning on wet tree trunks will increase the external pressure on your clothes. Moisture on the surface of the contact point may be “pressed” into the fabric.
For example, sitting on a wet surface will generate about 2000mm of hydrostatic pressure. A jacket needs to have high hydrostatic pressure to avoid getting your butt wet.
Therefore, mountaineering activities with heavy loads require a jacket with high hydrostatic pressure – because of the hydrostatic pressure of the jacket The demand for pressure is related to external pressure, and long-distance hiking with heavy loads is more likely to encounter sudden rain, so a jacket with high hydrostatic pressure is needed to avoid getting “wet”.
Since the hydrostatic pressure of a jacket is directly proportional to its waterproofness, does the higher the hydrostatic pressure, the better the jacket? No.
The breathability of the jacket also needs to be considered
It is inevitable to sweat a lot when climbing. If the sweat is not discharged in time, you will get soaked and feel uncomfortable. Therefore, in addition to being rainproof, the jacket also needs to be breathable. Rainproof is a safety requirement, and breathability is a comfort requirement. , but you often can’t have both, so you have to make a balanced choice.
Breathability is about comfort – the sweat emitted by the human body is transmitted to the outside world in the form of water vapor through the jacket, thereby preventing sweat from gathering and condensing inside the jacket. , is the key to the comfort of the jacket.
There is a “microclimate zone” between the human body and clothing. If the evaporated sweat of the human body cannot be discharged from the fabric, it will increase the water vapor in the microclimate zone. content, leading to an increase in relative humidity and even condensation of sweat, making the wearer feel hot, humid and uncomfortable. (Source: Lou Chenyu, “Research on Evaluation Methods for Waterproof and Breathable Functions of Jackets” 2016 Modern Textile Technology Issue 1)
The higher the waterproofness, the weaker the breathability – this is because the waterproofing and breathability of the jacket use the same channel – the membrane Micropores. The contradiction between the thickness of one and the thinness of the other creates a contradiction between the two: to improve the waterproofness, the micropores of the film need to be smaller and denser, which is less conducive to the evaporation and discharge of sweat. Therefore, the higher the waterproofness of the jacket, The weaker the breathability, vice versa.
When should high breathability be considered? Since the breathability of a jacket is inversely proportional to its waterproofness, in some rows For outdoor activities with high sweat requirements and low threat of rain and snow, such as cross-country running, you need to prefer a jacket with high breathability.
The high waterproofness and high breathability of the jacket are incompatible with each other. How should you choose?
Balancing the waterproofness and breathability of the jacket according to the activity
The waterproofness and breathability of the jacket cannot be achieved at the same time. When purchasing, you cannot expect to buy an “all-rounder” Jackets should be balanced according to your type of outdoor activities.
Cross-country running activities – cross-country running requires a jacket with high sweat wicking efficiency, so it must have high breathability; cross-country running requires little carrying, and a backpack is required in rainy weather The pressure on the jacket is small, so the waterproof requirements are low. Mountain enthusiasts can choose jackets from the GORE-TEX Active Products series.
Single-day hiking – The amount of exercise during a single-day hike is moderate, and the jacket does not require high-intensity perspiration; carrying a light bag in rainy weather will cause some damage to the jacket. pressure, so a jacket for one-day hiking should have a mid-range level of breathability and waterproofness, such as the GORE-TEX Products series.
Long-term heavy-duty hiking and high-altitude mountaineering—such activities require carrying heavy-duty bags. In extreme rain and snow, the jacket may be soaked due to the pressure of the backpack. , thereby bringing about the risk of hypothermia. Therefore, such activities require jackets with high waterproofness and compromise on breathability, such as GORE-TEX Pro series products.
Write it at the end
The waterproofness of the jacket depends on the hydrostatic pressure, but you can’t just pursue high hydrostatic pressure, you also need Consider breathability. There is a dilemma between waterproofing and breathability. According to different activity needs, a balanced choice between waterproofing and breathability is the way to choose a jacket.
