Water repellency has quality. How to check water repellency.

In youtube videos that verify the use and effectiveness of water repellents such as waterproof sprays and NIKWAX, you will see videos that show how water repellency is restored by dropping water on the surface after water repellent treatment, or by applying tap water, but evaluating water repellency is actually not as simple as that. Of course, it can be seen as a part of evaluating water repellency, but in reality, water repellency needs to be evaluated in a more complex and multifaceted manner, which will be described in this article.

Check the water repellency. (It is different from water repellency.)

The method to check water repellency is very simple. Just drop water on the jacket and check if it repels water. If it repels water, it can be said to have water repellent performance. Some people describe this as water repellency, but this is incorrect. Waterproofness refers to the property that water does not pass through even if water pressure is applied. Water repellency, on the other hand, is the ability of water itself to curl up and remain as droplets instead of being absorbed by the fabric. Water repellency and water resistance are two different physical phenomena.

Despite checking for water repellency

However, despite having been checked for water repellency, water may quickly seep into the fabric when used in actual rain.

This may involve two problems. (1) Poor water repellency checks, and (2) lack of consideration for sustainability.

(1) Lack of water repellency checks

Checks such as dripping water or exposing the jacket to tap water are lax checks for water repellency. Even if the water repellency is not very high, water can be repelled by these checking methods. Conversely, if water does not repel when the garment is exposed to dripping water or tap water, it is safe to say that the garment is not water-repellent at all for practical use. Since actual rain hits the garment more strongly, simply spraying water on the garment is insufficient.

2) Persistence of water repellency

Unfortunately, when we say we check water repellency, we are only checking the water repellency at the current moment. Water repellency decreases with use. It also depends on the conditions of use. It also affects the accuracy of the water repellent film coated on the jacket.

It is very difficult for the average user to check these factors. This is because manufacturers evaluate water repellency after subjecting the jacket to a number of stresses before selling it on the market. While water repellency treatments performed by ordinary users are easy to perform, the perfection of their water repellent coating films is not very good, and they quickly degrade.

Drop Roof was developed in response to this problem. We form a water-repellent coating film that cannot be reached by the average user, allowing us to provide water-repellent treatment with the same precision as jackets sold on the market. That is the DANSUI coating performed by Drop Roof.

Water Repellency Evaluation Index

There are several indicators of water repellency. A typical example is the spray test, which is defined in ISO and AATCC, and is rated on a scale of 0 to 5 for ISO, and on a scale of 0 to 100 for AATCC, which also has six levels.

Another way to look at it is to measure the contact angle. This is a method of measuring the contact angle when a certain amount of water is dropped on the surface. There are two ways to look at this: static contact angle and dynamic contact angle. The dynamic contact angle is the one that makes the difference more visible.

The Bundesmann rainfall test apparatus may also be used for testing that simulates actual rain. Recently, this evaluation has become the mainstream.

However, these tests are only limited. What we climbers need is water repellency to withstand several days of bad weather in the mountains. The tests introduced earlier are only initial evaluations, and we need to add the perspective of how far it can endure.

In other words, we need to look at the initial performance of water repellency x its staying power. The quality of water repellency is determined by the combination of both of these factors.

However, the durability is a bit tricky. You have to decide what you are looking for in terms of sustainability. In other words, what kind of stress do you expect? It could be friction, it could be strong rain, it could be dirt. There are various kinds of stresses, and each has its own strengths and weaknesses, so the evaluation may differ depending on where the tuning is set.

These are no longer evaluated by ISO or JIS, and each manufacturer makes their own evaluation. Some manufacturers conduct spray tests after applying mechanical stress and long Bundesmann rainfall tests. Several evaluations are conducted to assess lasting water repellency.

Conclusion.

Either way, water repellency needs to be evaluated from these perspectives and is quite complicated. So not just any water repellent treatment will do, we need to be concerned about the quality of the water repellent treatment. After treating with water repellent agents such as household waterproofing sprays or NIKWAX, we should not simply judge that water repellency has been restored by applying tap water.