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Waterproofing and DWR

From time to time, we have customers write us and mention that the “waterproofing” is gone from their dry suit or dry top, and they are wondering how to renew or refinish it. Since the term “waterproofing” in this context suggests incorrectly that the outer coating or finish on waterproof breathable garments is doing the heavy lifting in terms of keeping the garment dry, we wanted to write an article clearing up any misconceptions about how waterproof breathable fabrics work. We will also address different reasons why garments appear to be soaking through, and ways to remedy that.

Most dry tops and drysuits are made with what’s called a “3 layer” fabric. The 3 layers refer to the the outer shell fabric, a middle or “mid-layer’ waterproof breathable coating or laminate, and then on the inside of the garment a fine protective mesh or “tricot” glued to the mid-layer. The outer shell provides durability, the mid-layer is the waterproof barrier and the tricot protects the delicate mid-layer. Additionally, fabric manufacturers will almost always spray on a durable water repellant coating or “DWR” on the outer shell of the fabric as a final step. This DWR coating will make water bead off a garment for some period of time, but eventually will wear off.

The purpose of this DWR is to keep the outer shell from absorbing or holding water. When a shell starts to hold water, a couple of things happen that will adversely affect the “dryness” of a garment. The first is that a soaked shell will inhibit the breathability of the midlayer, making it easier for water vapor to remain trapped inside. The second is that a soaked shell is often very cool or even cold, making condensation far more likely inside a garment, especially a sealed garment like a dry top or dry suit. These things combined will often make a customer 100% convinced that a garment is “soaking through the fabric”, when in fact, the garment is still 100% waterproof.

To make matters worse, popular and very powerful DWR finishes from 10 years ago are now for the most part illegal to use in most of the developed world due to environmental and health concerns. Current DWR coatings on responsibly-made garments are far weaker, and only last for a short period of time.

Once these coatings wear off through exposure to dirt and oils or abrasion, your garment will lose it’s ability to bead water, and the outer shell fabric will start to wet out. There are after-market DWR coatings available from the IR website, and from most large outdoor sports retail chains. They work reasonably well, but not as good as the original (albeit weakened) DWR coating put on in the factory. These will be called things like “durable waterproofing” and are made by companies like Revive-X and Nikwax. There are two common methods of application – spray-on and wash in. Spray on is preferred because it’s only applied to the outside of the garment. Spray on DWR treatments allow you to target high wear areas like where you PFD straps rub. Wash in DWR applications will treat the inside and outside of the garment and can impair breathability.

You can also take into account the type of shell fabric used in a dry garment when shopping for a new suit or top. Outer shells made with polyester are more “hydrophobic” or shed water more quickly, as polyester does not readily absorb water. The downside of polyester is that it’s not as strong as the other common shell fabric material – nylon. Nylon shelled jackets are more abrasion resistant, but nylon thread is “hydrophilic” meaning that it’s more likely to absorb water. Note that polyester, even though considered “hydrophobic”, will not shed water like a DWR, but it will remain less saturated than a nylon shell.

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